COVID

I take COVID-19 spread prevention very seriously.  The Darren Difference COVID-19 Prevention Procedures and Precautions, were developed in conjunction with local and provincial health standards, local real estate boards, in addition to prevalent research on the Novel Corona Virus.  Please refer to Sections 5 and 6 for detailed information on COVID-19.

On This Page:

  1. Spread Prevention Precautions – Printed Marketing Materials and Documents
  2. Spread Prevention Precautions – Home Showings by Sellers
  3. Spread Prevention Precautions – Home Viewings by Buyers
  4. Spread Prevention Precautions – Client Meetings
  5. About the COVID-19 Virus.
  6. Spreading Mechanisms of the COVID-19 Virus.

Spread Prevention Precautions – Printed Marketing Materials and Documents

The main risks associated with printed marketing materials are fomite contamination, fomite spread, and aerosol contamination.  These procedures have been designed to address these concerns.

Home Distributed Materials

  • Post Printing, marketing materials are airtightly quarantined for a period of 14 days, to address fomite contamination from printing and aerosol contamination during the quarantine.
  • Marketing materials are removed from quarantine using clean, freshly laundered gloves, which are also sanitized using a product containing a minimum of 70% alcohol. Freshly laundered or new disposable face masks are worn in conjunction with gloves.  Marketing materials are placed in a sanitized or “soap & water” washed plastic container.
  • Transportation for distribution is done in a sanitizer container that is sanitized and/or “soap & water” washed, after each use. The internal surface of container only encounters post-quarantined marketing materials.
  • Laundered and sanitized gloves are used for distribution of printed materials. Gloves are frequently sanitized throughout the distribution event.  Gloves are replaced with a “fresh” pair of gloves for each distribution event.
  • A face mask or face covering is worn during distribution. Masks or coverings are replaced, laundered, or sterilized for every distribution event.
  • Efforts are made to minimize surface contact by using media such as Door Hangers which prevents the touching of external surfaces.
  • For Flyer or Newsletter distribution, glove contact surface of marketing material and glove contact service of mailbox is always separate and independent. Frequency of sanitizing of gloves is increased.

In-Home Materials

  • Display stands are freshly “soap & water” washed for each home. Delivery and utilization follow the same procedures as for all printed materials.
  • Post Printing, marketing materials are airtight quarantined for a period of 14 days, to address fomite contamination from printing and aerosol contamination during quarantine.
  • Marketing materials are removed from quarantine using clean, freshly laundered gloves, which are also sanitized using a product containing a minimum of 70% alcohol. Freshly laundered or new disposable face masks are worn in conjunction with gloves.  Marketing materials are placed in a sanitized or “soap & water” washed plastic container.
  • Transportation for distribution is done in a sanitizer container that is sanitized and/or “soap & water” washed, after each use. The internal surface of container only encounters post-quarantined marketing materials.

Client Materials

  • Post Printing, marketing materials are airtightly quarantined for a period of 14 days, to address fomite contamination from printing and aerosol contamination during the quarantine.
  • Client Materials refers to marketing materials provided to clients during meetings.

Documents

  • The utilization of electronic documents and the use of e-signatures, in accordance with the Electronic Commerce Act, 2000 (Ontario), are primarily used when applicable.

Spread Prevention Precautions – Home Showings by Seller.

  • In accordance with guidelines developed by Century 21 Canada, mandatory showing procedures are in place.
  • Before an appointment is booked, a Realtor must answer a list of questions and certify that they, and their client, are COVID-19 symptom-free and COVID-19 infection-free. In addition, they have not traveled out of the country in the past 14 days.
  • During said certification Darren, Century 21 Millennium, and the Home Seller is indemnified from liability due to infection.
  • During said certification, the Realtor must confirm adherence to a list of rules including – no use of bathrooms while on premises, no handling of light switches*, no handling of interior doorknobs*. (*when feasible)
  • All visitors are required to wear face coverings and gloves. If they do not have face coverings and gloves, they will be available, on premise, in addition to hand sanitizer, and sanitizing wipes.

Spread Prevention Precautions – Homes Viewings by Buyers.

  • During appointment booking, Darren must certify that himself and client(s) are COVID-19 symptom-free and COVID-19 infection-free, to the best of their knowledge. In addition, they have not traveled out of the country in the past 14 days.  During the certification, we indemnify the Listing Brokerage and Home Owner.
  • During said certification, we must confirm that we will adhere to a list of rules including – no use of bathrooms while on premises, no handling of light switches*, no handling of interior door knobs*. (*when feasible)
  • All visitors are required to wear face coverings and gloves. If they do not have face coverings and gloves, they will be available from Darren.

Spread Prevention Precautions – Client Meetings

  • Face to Face, indoor client meetings require face covers except for in cases where medical conditions prevent face coverings as allowed by the Province of Ontario.

Disclaimer: The COVID-19 prevention precautions and procedures, while developed with the best intentions, are not a guarantee against the spread of COVID-19 and no such claim is implicitly or explicitly conveyed or implied.   

Information Disclaimer:  The following information was developed by agencies independent and external to The Darren Difference, Darren Roopnarain, and all affiliates.  The application and use of this information are the responsibility of the user. The Darren Difference, Darren Roopnarain and any affiliates assume no liability resulting from any such application or use. 

About the Covid-19 Virus.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)[2][3] is the strain of coronavirus that causes coronavirus disease 2019 (COVID-19), the respiratory illness responsible for the COVID-19 pandemic. Colloquially known as simply the coronavirus, it was previously referred to by its provisional name, 2019 novel coronavirus (2019-nCoV),[4][5][6][7] and has also been called human coronavirus 2019 (HCoV-19 or hCoV-19).[8][9][10][11] The World Health Organization declared the outbreak a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020.[12][13]

SARS-CoV-2 is a Baltimore class IV[14] positive-sense single-stranded RNA virus[15] that is contagious in humans.[16] As described by the U.S. National Institutes of Health, it is the successor to SARS-CoV-1,[10][17] the strain that caused the 2002–2004 SARS outbreak.

Taxonomically, SARS-CoV-2 is a strain of severe acute respiratory syndrome-related coronavirus (SARSr-CoV).[2] It is believed to have zoonotic origins and has close genetic similarity to bat coronaviruses, suggesting it emerged from a bat-borne virus.[18][19][20][9] There is no evidence yet to link an intermediate host, such as a pangolin, to its introduction to humans.[21][22] The virus shows little genetic diversity, indicating that the spillover event introducing SARS-CoV-2 to humans is likely to have occurred in late 2019.[23]

Epidemiological studies estimate each infection results in 5.7 new ones when no members of the community are immune and no preventive measures taken.[24] The virus primarily spreads between people through close contact and via respiratory droplets produced from coughs or sneezes.[25][26] It mainly enters human cells by binding to the receptor angiotensin converting enzyme 2 (ACE2).[18][27][28][29]

Source: https://en.wikipedia.org/wiki/Severe_acute_respiratory_syndrome_coronavirus_2

Spreading Mechanisms of the Covid-19 Virus

Key Points

 The predominant mode of transmission of COVID-19 is via respiratory droplets during close unprotected contact

 Airborne spread has not been a dominant or common mode of transmission. Aerosols may be generated during aerosol generating medical procedures (AGMPs), which may increase the risk of transmission.

 Transmission through the ocular surface is considered a possible route of transmission for COVID-19.

 COVID-19 can survive on surfaces and may be transmitted via fomites. The extent that fomites contribute to transmission is unknown.

 COVID-19 has been detected in stool and blood, however the roles of fecal-oral and bloodborne transmission remain uncertain.

 There is evidence to suggest that vertical transmission (mother to child) may occur under certain circumstances, but further studies are needed. While viral RNA has been inconsistently documented in breast milk, there is no evidence to date of transmission from mother to child through breast milk. Vertical transmission and transmission through breast milk are considered uncommon modes of COVID-19 transmission.

 

The purpose of this document is to outline what is known about how COVID-19 is transmitted from person-to-person, based on a review of the scientific literature. The virus responsible for COVID-19, SARS-CoV-2, is genetically similar to other coronaviruses. In particular, it shares a high degree of genetic similarity (79%) (Lu R et al.), with the coronavirus (SARS-CoV-1) responsible for Severe Acute Respiratory Syndrome (SARS). Therefore, in instances of limited evidence for COVID-19, we have extrapolated existing data from other coronaviruses, in particular SARS-CoV-1.

Droplet and Contact Transmission Current evidence suggests that the primary mode of transmission of COVID-19 is through direct contact from respiratory droplets that have the potential to be propelled for varying distances (Centers for Disease Control and Prevention (CDC), European Centre for Disease Prevention and Control (ECDC), Imai et al., Schneider et al., Wilson et al.).

 The majority of COVID-19 cases have been linked to person-to-person transmission through close direct contact with someone with respiratory symptoms (e.g., Burke et al., Chan et al., ECDC, Pung et al.) or close contact with a case in the incubation period who was later confirmed to have COVID-19 (Huang R et al., Tong et al., Yu P et al.).High viral loads have been identified in individuals who were asymptomatic or pre-symptomatic (Arons et al., Chau et al., Wei et al.).  A report by the World Health Organization (WHO) Joint Mission on Coronavirus Disease 2019 (COVID-19) in China summarizes the experience with 75,465 cases and indicates that the route of transmission is droplet during close unprotected contact (WHO).  Respiratory droplets have been shown to be propelled up to 2 m (Schneider et al.) and in one study was found on the floor up to 13 ft (or 4 m) away from the patient (Guo et al.). A systematic review of studies assessing the horizontal distance travelled by respiratory droplets found that droplets can travel more than 2 m and up to 8 m (Bahl et al.).

Airborne Transmission Respiratory virus transmission occurs on a spectrum from larger droplets that spread at close range to smaller droplets (or aerosols) that have the potential to be infectious over longer distances and may be suspended for longer periods of time. As summarized above, current evidence supports that COVID-19 transmission is predominately through close, unprotected contact, which supports larger droplet spread. A recent commentary in Clinical Infectious Diseases appealed to the medical community to recognize the potential of airborne transmission based on experimental evidence that small respiratory droplets (or aerosols) could be inhaled. Another commentary in the Journal of the American Medical Association discusses how the balance of currently available evidence does not support long-range aerosol transmission as the dominant mode of COVID-19 transmission. While aerosols are produced during activities such as speaking, breathing and coughing (Stadnytskyi et al.), it is not clear what role in transmission these have for distances greater than 2 m as viable SARS-CoV-2 has not been detected during air sampling. The role of these aerosols has been suggested in a modelling study to be most important for transmission in close proximity (within 2 m) (Chen W et al.).

Experimental evidence of aerosol generation:  In a study comparing SARS-CoV-2 and SARS-CoV-1, van Doremalen et al. reported that SARSCoV-2 could be artificially aerosolized with a jet nebulizer and detectable for up to three hours in a rotating metal drum. The half-lives of SARS-CoV-2 and SARS-CoV-1 were similar in aerosols with median estimates of the half-life of 1.1-1.2 hours. While the van Doremalen et al. study concluded that aerosol transmission is possible, they did not demonstrate that it occurs (refer to the PHO Synopsis on this study for further details). Similar conclusions were drawn from a study conducting a similar experiment (Fears et al.).  Environmental exposures, such as sunlight, may have significant effects on viability of SARS-CoV2. Using a rotating drum experiment similar to other studies for viability of SARS-CoV-2, simulated sunlight (UVA/UVB) was applied to aerosolized virus through a window on the drum. Results indicated 90% inactivation of virus within 20 minutes supporting indoor environments as higher risk for transmission (Schuit et al.).

Secondary attack rates and epidemiologic reports are not consistent with airborne spread:   A report from the WHO China Joint Mission on COVID-19 summarizing 75,465 cases indicates that airborne spread has not been reported (WHO). This report stated that the majority of COVID-19 transmission in China occurred within households. Of all of the infection clusters investigated, 78-85% were within households, with a secondary attack rate of 3-10%. The absence of significant clusters in non-household settings suggests that the mode of COVID-19 transmission is not airborne. For comparison, the household secondary attack rates for measles are > 90%.  An article describing the active follow-up of 445 close contacts to the first ten cases of COVID-19 in the United States described two cases of secondary transmission only to close household contacts. Of the 445 close contacts, 19 (4%) were household members, 104 (23%) were community members who spent at least 10 minutes in close proximity to the case, 100 (22%) were community members exposed in a healthcare setting and 222 (50%) were healthcare workers. The symptomatic secondary attack rate of 0.45% (2/445) among all contacts and a symptomatic secondary attack rate for all household contacts of 10.5% (2/19) (Burke et al.).   Epidemiological COVID-19 transmission studies of thousands of secondary household contacts have identified attack rates between 7% and 23%. Non-household close contacts have secondary attack rates <1% (Bi et al., Cheng HY et al., Li W et al., Wang Y et al.). The limited transmission to contacts outside the household setting suggests that the mode of COVID-19 transmission is not airborne.   The reproductive number (R0) is less suggestive of airborne spread—airborne infections tend to have a higher R0. For example, in a systematic review (Guerra et al.) the R0 for measles in the prevaccine era was 6.1-27.0; compared to the range of R0 (2-3) reported for COVID-19 (Park et al.).

Studies have not consistently detected virus in air samples:   Multiple air sampling studies around confirmed COVID-19 cases were unable to detect any virus by PCR (Cheng V et al., Faridi et al., Ong et al., Wu S et al.).   Santarpia et al. was unable to culture virus from air samples collected outside of patient rooms.  Cheng V et al. sampled air at a high flow rate 10 cm from the chin of symptomatic and asymptomatic patients (n=6). No viable virus was detected by culture from collected air samples.   One study detected SARS-CoV-2 by PCR in 38.7% (14/31) of air samples from a London, England hospital during the peak of their epidemic. However, no virus was detected by culture suggesting there may not be adequate virus present in these air samples to cause transmission (Zhou et al.).

 Another study detected SARS-CoV-2 by PCR in 35% (14/40) air samples in the intensive care unit (ICU) and 12.5% (2/16) air samples on the general ward where patients with COVID-19 were managed. 15/16 PCR positive air samples were from within 2 m of the patients, with 1/8 samples positive at 4 m away (Guo et al.).  Chia et al., an extended study of Ong et al., detected genetic material of SARS-CoV-2 by PCR in the air within 1 m from patients in two of three airborne infection isolation rooms.

Long distance spread is uncommon:   An investigation of a COVID-19 outbreak in a restaurant in Guangzhou, China of three families sitting in close proximity for more than 1 hour concluded that the air conditioning (AC) ventilation likely contributed to droplet transmission (Lu J et al.). While this article is often used to support airborne transmission of COVID-19, there is more evidence to support transmission via respiratory droplets:  In this scenario, there was between 53-73 minutes of close contact between the presymptomatic index case and secondary cases.   The location of a consistently running AC unit (the outlet and exhaust flanked the index cases’ table) was in the airflow path of the secondary cases and was in an enclosed environment. No secondary cases occurred at adjacent tables that were outside of the likely “air column.”   The furthest distance between index and secondary cases was approximately 3 m (the authors state that droplets fall at <1-m distance, which is quite conservative).  The authors concluded that droplet transmission was in fact the most likely mode, with mechanical propulsion (not airborne spread).  The minimal transmission to passengers seated nearby cases who have travelled on airplanes does not support an airborne transmission route of COVID-19 (Schwartz et al., Chen et al., Yang N. et al.).

Airborne Transmission during AGMPs While airborne transmission has not been documented under routine circumstances (i.e., such as in households and in routine patient care), medical procedures that generate aerosols may be associated with an increased risk of transmission (Tran et al.).

 Two experimental studies have documented the stability of SARS-CoV-2 aerosols:  In the study by van Doremalen et al., aerosols were created experimentally (threejet nebulizer and Goldberg drum) and SARS-CoV-2 was found to survive up to three hours, supporting that aerosols may play a role in COVID-19 transmission.  In the study by Fears et al., aerosols were created experimentally (three nebulizers: the Collision 3-jet, Collision 6-jet and Aerogen Solo) for three coronaviruses (MERS, SARS-CoV-1 and SARS-CoV-2) and SARS-CoV-2 was found to survive up to 16 hours.  Two case series of exposures to COVID-19 patients during AGMPs have not demonstrated transmission to healthcare workers using droplet/contact precautions (Ng et al., Wong SC et al.).  During the SARS outbreak in 2003, infections disproportionately occurred among healthcare workers, with those involved in aerosol-generating procedures and manipulation of the airway (i.e. at the time of intubation) at greatest risk (Booth CM et al.). An investigation into a nosocomial outbreak of SARS in Toronto concluded that the epidemiological links described in their investigation support the theory that SARS is transmitted primarily through respiratory droplets and direct contact, noting that transmission occurred during high risk procedures (i.e. intubation) when only a surgical mask was utilized, in the absence of protective eyewear (Varia et al.). Iinfected healthcare workers were no less likely to contract SARS while wearing an N95 (vs. surgical mask), suggesting that it was most likely doffing (droplet/contact) where transmission occurred (Smith et al.).  More information on what is currently known about COVID-19 and the risks to healthcare workers can be found in the WWKSF document on the Risks to Health Care Workers.

Conjunctiva Transmission through the ocular surface is considered a possible route of transmission for COVID-19 based on recent case reports and evidence of virus detection from the eye among cases with conjunctivitis (Dockery et al.).

Infection acquired through the conjunctiva:  In a case report, the authors describe a healthcare worker who became infected with COVID-19 after visiting a patient; the health care worker was wearing an N95 respirator, but no eye protection. The health care worker developed eye redness and then pneumonia (Lu C et al.).   In a recent meta-analysis by Chu et al., eye protection provided significant protection against coronavirus infections (unadjusted RR: 0.34, 95% CI: 0.22-0.52), suggesting that transmission through the conjunctiva is possible. See PHO’s synopsis of Chu et al. for further information.

Conjunctivitis as a symptom of COVID-19 infection – viral RNA detection:  In one study of 30 confirmed COVID-19 cases with pneumonia, tear and conjunctival secretions were collected twice from each patient and tested using reverse transcription polymerase chain reaction (RT-PCR) assays. Only one patient had conjunctivitis with one of two samples yielding a positive RT-PCR result. The remaining 58 samples from all other patients were negative (Xia et al.).   In a series of 33 COVID-19 patients without ocular manifestations, two (6.1%) tested positive for viral RNA in ocular surface swabs (Xie et al.).  Wu P et al. reported that 2 of 28 (7.1%) COVID-19 patients had conjunctival swabs positive for viral RNA and both had ocular manifestations.  Zhang X et al. reported that 2 of 78 (2.6%) patients with laboratory-confirmed COVID-19 had conjunctivitis and one of these two patients had ocular discharge positive for viral RNA.  In a prospective cases series in Iran, viral RNA was detected in three of 43 patients with severe COVID-19, including one with conjunctivitis (Karimi et al.).   In Italy, a COVID-19 patient had ocular swabs tested almost daily during hospitalization; viral RNA was detected up to day 21 (and on day 27) of hospitalization (Colavita et al.).  Several studies failed to detect viral RNA in ocular secretions:  Recently, Deng et al. reported that none of the conjunctival swabs taken on 114 COVID-19 patients of varying disease severity tested positive for viral RNA using RTPCR.  In Singapore, viral RNA was not detected in the tears collected between days 3 and 20 after symptom onset from 17 COVID-19 patients (1 with ocular symptoms) (Seah).

Conjunctivitis as a symptom of COVID-19 infection – live virus detection:  To our knowledge, the study by Colavita et al. is the only instance where live virus was isolated from conjunctival swabs and produced a cytopathic effect on Vero E6 cells.

Fomite Transmission COVID-19 can survive on a variety of surfaces and may be transmitted via fomites. The CDC states “It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes. This is not thought to be the main way the virus spreads, but we are still learning more about how this virus spreads.” The evidence for fomite transmission of COVID-19 is not strong, as evidenced by a low household attack rate for COVID-19 and a single observational study that hypothesized that fomites were key in spread.

 From a detailed investigation, including whole genome sequencing, into an interfacility outbreak of up to 135 nosocomial COVID-19 cases (including 88 staff and 47 patients) in South Africa, Lessells et al. concluded that a patient in the emergency room likely spread the infection to at least five hospital units, a local nursing home and an outpatient dialysis unit on campus. Based on the pattern of transmissions, the authors of this report concluded that indirect contact and fomite transmission were the predominant modes of patient-to-patient transmissions, facilitated by frequent patient movements between wards.

Viral RNA detection:  Studies have documented the presence of viral RNA on surfaces in the environment of patients who have tested positive for COVID-19 (Chia et al., Jiang et al., Ong et al., Wu S et al.).   In a hospital in Wuhan, China, Ye et al. reported that the most contaminated surfaces were selfservice printers for patient use, keyboards and doorknobs.  In Italy, viral RNA was detected on the external surface of Continuous Positive Airway Pressure (CPAP) helmets worn by COVID-19 patients; however, samples inoculated on Vero E6 cells did not produce a cytopathic effect (Colaneri et al.).  A study reported viral RNA on surfaces (keyboards, telephones and scanners) in a clinical microbiology laboratory testing COVID-19-patient respiratory samples (Bloise et al.).

Surface stability of virus:  van Doremalen et al. compared surface stability of SARS-CoV-2 and SARS-CoV-1. The results of this study were recently summarized in a PHO Synopsis. An exponential decay in virus titre was seen for both viruses in all experimental conditions:  At 40% relative humidity and 21-23°C, both SARS-CoV-2 and SARS-CoV-1 were detectable for up to 24 hours on cardboard and up to two to three days on plastic and stainless steel. On copper, live SARS-CoV-2 and SARS-CoV-1 were not found after four hours and eight hours, respectively.  The estimate median half-lives for SARS-CoV-2 on these surfaces were 0.7 hours for copper, 3.5 hours for cardboard, 5.6 hours for stainless steel, and 6.8 hours for plastic. While the van Doremalen et al. study concluded that fomite transmission is possible given detection of SARS-CoV-2 on a number of surfaces, they did not demonstrate that it occurs.  Chin et al. investigated the surface stability of SARS-CoV-2 at 22°C and 65% relative humidity. Infectious virus could not be detected from inoculated printing and tissue paper after three hours after inoculation. Infectious virus was no longer present on glass or paper money by day 4 and on day 7 for plastic and stainless steel. The authors state “The virus is highly stable at 4°C, but sensitive to heat. At 4°C, there was only around a 0.7 log-unit reduction of infectious titre on day 14. With the incubation temperature increased to 70°C, the time for virus inactivation was reduced to 5 mins… SARS-CoV-2 can be highly stable in favourable environments, but it is also susceptible to standard disinfection methods.”  A couple of studies report conflicting results on the stability of SARS-CoV-2 at different temperatures; however, different methodologies were used:  Kratzel et al. found no major differences in stability of SARS-CoV-2 on metal surfaces at 4oC, room temperature (undefined) and at 30oC. Infectious virus was still detectable after 180 hours on metal surfaces at these temperatures. This study suspended the virus in bovine serum albumin, which does not represent natural conditions.  Matson et al. showed that SARS-CoV-2 in nasal mucus and sputum on surfaces was more stable in cooler and lower humidity conditions (4oC and 40% relative humidity) than in warmer and more humid conditions (27oC and 85% relative humidity).

Fecal-oral Transmission While the viral RNA and live virus have been detected in the stool of patients with COVID-19, the role of fecal-oral transmission remains uncertain.

Background:  As part of early investigations of the outbreak, SARS-CoV-2 has been detected and isolated in the intestinal tissues of animals challenged with the virus (WHO).    Tissues in the oral cavity express angiotensin-converting enzyme 2 (ACE2) receptors that are believed to be used by SARS-CoV-2 to enter cells (Xu H et al.). ACE2 receptor expression has also been documented in gastrointestinal epithelial cells (Xiao et al.).   It has been reported that a relatively small proportion of patients experience diarrhea and vomiting during COVID-19 infection (e.g., Chen N et al., Guan et al., Wang D et al.), with case reports of gastrointestinal symptoms in the absence of respiratory symptoms (Hosoda et al., Song Y et al.).  More information on fecal-oral transmission can be found in the What We Know So Far (WWKSF) document on fecal-oral transmission.

Viral RNA detection:  SARS-CoV-2 RNA has been detected in stool in various studies (Chen L et al., Chen Y et al., Han et al., Pan Y et al., Tang et al., Wu et al., Xu Y et al.), with prolonged shedding for over 3 weeks reported in some (Han et al., Wu et al., Xu Y et al.). Severity of COVID-19 was not associated with duration of viral shedding in stool.  A case report found SARS-CoV-2 RNA detection and intracellular staining of viral nucleocapsid protein in gastric, duodenal, and rectal epithelia demonstrating that SARS-CoV-2 infects these gastrointestinal glandular epithelial cells (Xiao et al.).  In a cohort study in Hong Kong, 15/59 (25.4%) of patients with COVID-19 had gastrointestinal symptoms and viral RNA was detected in 9 of these patients (Cheung et al.). The authors performed an additional meta-analysis of 4,243 COVID-19 patients, amongst whom the prevalence of gastrointestinal symptoms was 17.6% (95% CI: 12.3-24.5) and presence of viral RNA in stool was 48.1% (95% CI: 38.3-57.9).

 A systematic review noted that in combined studies, 53.9% (291/540) of COVID-19 patients had viral RNA-positive fecal samples (Gupta et al.). Duration of fecal shedding ranged from 1 to 33 days after negative NP swabs.  In a meta-analysis, Wong MC et al. reported a pooled detection rate of viral RNA in fecal samples among patients was 43.7% (95% CI: 32.6-55.0).  The WHO-China Joint Mission document notes that viral RNA has been detected in feces in up to 30% of patients from day 5 following onset of symptoms and in some cases has been detected for up to 4-5 weeks (WHO).

Live virus detection:  Live virus has reportedly been cultured from stool for up to several weeks (e.g., Wang W et al., Xiao, Sun et al., Zhang Y et al.). It is important to note that positive and negative controls in these studies were not defined.

Bloodborne Transmission While viral RNA has been detected in the blood, the role of bloodborne transmission remains uncertain.

 Several studies have reported detection of SARS-CoV-2 RNA, in either plasma or serum (e.g., Chan et al., Han et al., Huang C et al., Wang W et al.).  In Germany, viral RNA was not detected in whole blood or serum of 18 asymptomatic and symptomatic COVID-19 patients; however, viral RNA (low level RNA: 179 copies/mL) was detected in the plasma of one patient (Corman et al.).  More information on bloodborne transmission can be found in the WWKSF document on bloodborne transmission.

Vertical Transmission To date, there is some evidence to suggest that vertical transmission of COVID-19 may occur from mother to child. However, there are no confirmed cases (i.e. SARS-CoV-2 detection in umbilical cord tissue or blood) in the literature to date. The reported case series suggest that it is not a common occurrence and the case reports indicate that it may only occur under certain conditions.

The following studies have shown no evidence of vertical transmission:   In a meta-analysis of 87 pregnant women with COVID-19, there was no evidence of vertical transmission (Kasraeian et al.).  In a systematic review including 310 births, there was no evidence of vertical transmission (Huntley et al.).  In a study of 60 pregnant women with COVID-19, none of the 23 neonates tested positive by PCR; none of the neonates contracted COVID-19 through breastfeeding and viral RNA was not detected by PCR in placental tissue (Pereira et al.).  Khan et al. reported no vertical transmission after three pregnant women with COVID-19 delivered naturally; children had normal birth weights, lengths, Apgar scores, and tested negative for SARS-CoV-2 by PCR.   Yan et al. reported no vertical transmission in a series of 99 mothers with COVID-19 (laboratory confirmed + clinically diagnosed), no children (n=100) tested positive by PCR for COVID-19.   Qiancheng et al. reported no vertical transmission in 28 pregnant women and 23 newborns. All newborns had two negative PCR tests and no evidence of pneumonia.

 Zhu H et al. reported no vertical transmission after nine pregnant women with COVID-19 delivered; findings were confirmed with throat swabs for PCR taken at one to nine days after birth in 9/10 newborns and there was no evidence of vertical transmission.  Fan et al. reported no vertical transmission after two pregnant women with COVID-19 delivered and both infants were in good health and negative testing by PCR.   Chen R et al. reported no vertical transmission after 17 pregnant women with COVID-19 delivered via Caesarean section. Three births were premature, but newborns were over 2500 g and children were discharged in good health following brief observation in the neonatal intensive care unit. Lack of infection was confirmed with nasal swabs for PCR performed one day after birth and again on the day before discharge.  Chen H et al. reported no vertical transmission after nine pregnant women with COVID-19 pneumonia delivered via Caesarean section. SARS-CoV-2 could not be detected by PCR in amniotic fluid, cord blood, breast milk, or from neonatal throat swabs.  Chen Y, Peng H, et al. reported no vertical transmission in three pregnant women with COVID19; newborns tested negative by PCR from throat swabs.   Liu Y, Chen H, et al. reported no vertical transmission after 10 pregnant women with COVID-19 delivered via Caesarean section. There was no clinical or serologic evidence suggestive of vertical transmission (the serological test used was not reported).  Li Y et al. reported no vertical transmission after a pregnant woman with COVID-19 delivered via Caesarean section. An oropharyngeal swab, obtained immediately after birth, indicated the newborn was negative by PCR. During the next 2 days, the infant’s oropharyngeal swab, blood, feces, and urine samples remained negative for SARS-CoV-2 by PCR throughout testing at seven different time points.  Xiong et al. reported no vertical transmission in a child born by vaginal birth to mother with COVID-19; amniotic fluid, neonate throat swab and rectal swab were negative for viral RNA by PCR testing.   Liu W et al. reported no vertical transmission after delivery in 19 mothers with COVID-19 (laboratory confirmed + clinically diagnosed); neonates tested negative by PCR (throat swab, urine, feces);) amniotic fluid and breast milk also tested negative by PCR.   Yang P et al. reported no vertical transmission in seven pregnant women with COVID-19; neonates tested negative on throat swabs and/or amniotic fluid by PCR.

The following studies provide some evidence that vertical transmission of COVID-19 may occur:   Knight et al. report the results from a prospective national population based cohort study using the UK Obstetric Surveillance System (UKOSS), which included 427 pregnant women admitted to hospital with confirmed SARS-CoV-2 infection. Twelve (5%) of 265 infants tested positive by PCR for SARS-CoV-2, 6 of whom within 12 hours of birth. No viral analyses were performed on the umbilical cord blood, placenta or vaginal secretions. Infection prevention and control practice after birth were not described.  Zeng L et al. reported possible vertical transmission in 3 of 33 neonates who were born to mothers with confirmed COVID-19 pneumonia. They report that because ‘strict infection control and prevention procedures were implemented during the delivery’ it is likely that the source of infection was maternal, but details of these practices are not provided. Neonates were diagnosed by PCR on swabs done on Day 2 of life.   Zeng H et al. reported possible vertical transmission in 2 of 6 neonates who were born to mothers with COVID-19 pneumonia at Zhongnan Hospital of Wuhan University and delivered via Caesarean section. All mothers wore masks, and all medical staff wore protective suits and double masks. The infants were isolated from their mothers immediately after delivery. Neonatal throat swabs and blood samples collected at birth all had negative PCR test results. All 6 infants had antibodies detected in their serum, 2 infants had IgG and IgM concentrations higher than the normal level (<10 AU/mL).    Dong et al. reported potential vertical transmission in a newborn who was born to a mother at 34 weeks gestation with COVID-19 and delivered via Caesarean section. The mother wore an N95 respirator and did not hold the infant. The neonate had no symptoms and was immediately quarantined in the neonatal intensive care unit. At 2 hours of age, the COVID-19 IgG level was elevated at 140.32 AU/mL and the IgM level was also elevated at 45.83 AU/mL. Nasopharyngeal swabs taken from 2 hours to 16 days of age were negative by PCR.   Alzamora et al. reported possible vertical transmission in a newborn born by Caesarean section to a mother with COVID-19 pneumonia (4 days of symptoms). The infant was isolated immediately after birth without delayed cord clamping or skin-to-skin contact. Nasopharyngeal swab at 16 hours of life was positive for COVID-19 by PCR. The serology testing for IgM and IgG were negative.   Ferrazi et al. reported potential vertical transmission in 2/10 vaginal births and 1/8 Caesarean section births. In one vaginal birth, the child was isolated from mother immediately after birth and developed symptoms of COVID-19 on day 3 and tested positive by PCR.   Yu N et al. reported unlikely vertical transmission after one of three neonates delivered via Caesarean section tested positive by PCR. Thirty six hours after birth, COVID-19 virus was not detected in the placenta or cord blood by PCR.  Hu et al. reported that COVID-19 detected in one of the seven births examined was potentially due to vertical transmission. Amniotic fluid from all cases was negative by PCR and all children were isolated from mothers after birth. The neonate, who was exclusively formula-fed, tested positive on throat swab by PCR taken 36 hours after birth but subsequent throat swabs and blood, urine and feces tested negative by PCR.  Mehta et al. reported on a possible case of vertical transmission, where one of two twin babies tested positive on throat swab by PCR 72-hours after birth. The placenta and umbilical cord were not tested.    Sun et al. reported potential vertical transmission in one of three mothers with COVID-19. The neonate tested positive by PCR on day 6 of life; however, it is not clear if transmission occurred during Caesarean section, while in the operating theatre or recovery room, or when being cared for by family.   Gordon et al. report a case of possible vertical transmission of SARS-CoV-2 from a mother presenting at 32 weeks gestation with fever, cough, lymphopenia and positive swab for SARSCoV-2 by PCR. The baby was born via emergency Caesarian section and separated immediately after birth from the mother who wore a mask during delivery. The baby remained in the neonatal intensive care unit and had no contact with the mother, father or any family member. While the initial swab was negative by PCR on day 1 of life, the infant had a positive swab by PCR on days 4, 14 and 21.  Kirtsman et al. reported a case of probable vertical transmission SARS-CoV-2 infection in a neonate born to a mother who tested positive for SARS-CoV-2 by PCR on nasopharyngeal swab and was put on airborne, droplet and contact precautions. The mother had a history of familial neutropenia, gestational diabetes and frequent bacterial infections and presented with fever, myalgia, decreased appetite, fatigue and cough in the 24 hours prior to admission. The baby was born by semi-urgent Caesarean section and was placed in a resuscitator 2 m away from the mother. The NP swab was positive for SARS-CoV-2 by PCR at birth, day 2 and day 7. Neonatal plasma was positive by PCR on day 4 and stool on day 7. However, SARS-CoV-2 was not detected by PCR on the umbilical cord tissue and cord blood was not available for testing.  Evidence of placental involvement:  Li M et al. found that ACE2 (the receptor which SARS-CoV-2 binds to enter cells) was highly expressed in maternal-fetal interface cells in the placenta and also expressed in specific cell types of human fetal heart, liver and lung, but not in kidney. This was based on single-cell RNA sequencing (scRNA-seq) data available online which was used to evaluate the cell specific expression of ACE2.  Patanè L et al. concluded that viral RNA was found by PCR on the fetal side of the placenta in two mothers infected with COVID-19. Both children were also positive by PCR upon nasopharyngeal swabs taken at birth.  Hosier et al. analyzed the placenta from woman in her second trimester with symptomatic COVID-19 complicated by preeclampsia and placental abruption. SARS-CoV-2 was detected by PCR predominantly in the syncytiotrophoblast cells at the maternal-fetal interface of the placenta.

Breastfeeding Transmission Currently, there is no evidence to support mother-to-child transmission of COVID-19 during breastfeeding. While viral RNA has been detected by PCR inconsistently in studies examining breast milk, live virus has not been detected and there have been no documented cases where breast milk is the suggested mode of transmission to an infant. However, during breastfeeding, an infected mother can transmit COVID-19 to the child through respiratory droplets and close-contact transmission.

 In several studies of mothers with COVID-19, breast milk was negative for viral RNA by PCR (e.g., Chen H et al., Dong et al., Liu W et al., Li Y et al.).   A case report detected viral RNA by PCR in the breast milk of a breastfeeding mother with COVID-19 infection (Tam et al.). The breastfed child developed symptoms one day after his mother, at which time he tested positive by PCR on nasopharyngeal swab. The transmission route in this case could not be established.   Groß et al. report a study of two women who tested positive for SARS-CoV-2 by PCR after birth and were breastfeeding. Breast milk was positive by PCR in one of the two women at 10-13 days after birth. They did not attempt to culture the virus and therefore viability is not known. Both infants tested positive for SARS-CoV-2 by PCR (at day 8 and 11), but it is unknown if breastfeeding led to the infection in one of the infants as the two women and infants had shared a room for some time after delivery.  In a series of five pregnant women, viral RNA was detected in the breast milk by PCR of one woman (Zhu C et al.). In another study of two patients, viral RNA was detected by PCR in one lactating mother (Costa et al.). However, neither study attempted to culture the virus and therefore viability is not known.

Sexual Transmission Jing et al. reviewed the literature on ACE2 expression in the female reproductive system and noted expression of ACE2 receptors in the vagina. ACE2 receptors are also present in testes (Wang and Xu). While receptors for SARS-CoV-2 are present in reproductive organs, currently there is no evidence for sexual transmission of COVID-19, nor has live virus been detected in semen or vaginal secretions.

However, sexual transmission may occur through direct contact and through respiratory droplets and saliva.

 Li et al. reported that 15.8% (6/38) of male COVID-19 patients had viral RNA present in their semen; specimens were collected from two clinically recovered patients and four patients at the acute stage of infection. Viral RNA was detected by PCR up to 16 days after the onset of symptoms. For further information, please see PHO’s synopsis of Li et al.  Several studies have failed to detect COVID-19 viral RNA by PCR in semen and vaginal secretions of COVID-19 patients (Pan et al., Qiu et al., Song C et al.).  In a case report from Italy, viral RNA was not detected by PCR in the semen and urine of a confirmed case of COVID-19 (Paoli et al.).  Based on viral detection in feces, COVID-19 could be transmitted through certain sexual behaviours involving oral-anal contact (Patrì et al.).   In addition, viral RNA by PCR and live virus by culture has been detected in the saliva of COVID19 patients (e.g., Pasomsub et al., To, Tsang, Yip et al., To, Tsang, Leung et al.).

Appendix Glossary of Terms for COVID-19 Routes of Transmission

Advisory The glossary below contains definitions that may be fluidly changing with the understanding of evidence. Definitions may be different from how the same terms are used in other contexts or even seen as controversial due to different use within the same context by different organizations. Therefore, these definitions are provided to support the understanding of the COVID-19 – What We Know So Far About… Routes of Transmission document. This glossary is not exhaustive and may be updated with new terms or revised at any time.

Key Terms Airborne transmission: Transmission of infection occurring due to the inhalation of aerosols that have remained suspended for a long period of time or have been suspended on air currents over long distances.

Air sampling for virus: Collection of volumes of air by a device to determine if aerosols may contain virus. Collection can vary by aerodynamic size captured, duration of collection, volume per second collected, and media on which samples deposit. Air samples are can then be tested by molecular methods and/or viral culture.

Aerosol: Aerosols are defined by NIOSH as a suspension of particles (solids) or droplets (liquids) in the air.1 The diameter of microorganism-containing aerosols relevant to inhalation ranges from 0.01 to 100 μm. Discussion of respiratory infections focus on droplets rather than particles because the sources of infectious aerosols are assumed to be from respiratory mucosa or epithelium, which will be droplets (liquids) that contain infectious biological material. Droplets >100um are too large to be suspended in the air, and are therefore not considered aerosols.2 Droplets generally lose mass while suspended in air as aerosols due to evaporation of volatile components or water. The droplets that result from the process of evaporation are often referred to as droplet nuclei. The final size of a droplet will depend on a variety of environmental factors.

Aerosol generating medical procedures: Aerosol generating medical procedures (AGMPs) are defined as medical procedures that result in the production of aerosols that create the potential for airborne transmission of infections that may otherwise only be transmissible by the droplet route, and are epidemiologically associated with an increased risk of acquisition of infection.3

Contact transmission: Transmission of infection through direct contact.

Direct transmission: Transmission of infection through contact or droplet transmission.

Droplet transmission: Transmission of infection occurring due to impaction of large droplets (usually >100 um) that are too large to be suspended in air for long durations. Infection may follow by direct impaction onto mucosal surfaces (mouth, eyes, nose), or contaminate a person’s body/clothing which then makes direct or indirect contact with susceptible surfaces (e.g., mucosal surfaces for COVID-19).

Indirect transmission: Includes any mode of transmission where direct contact or droplet transmission is not involved (e.g., fomite transmission, airborne transmission, and vectors).

Fomite/Fomite transmission: Objects that may become contaminated with microorganisms and serve as vehicles of transmission.4

Polymerase Chain Reaction (PCR): A molecular method used to amplify nucleic acids. If nucleic acids of the microorganism of interest is present in a sample, then PCR can be used for the identification of that microorganism. This method cannot determine whether or not the microorganisms detected are viable.

Viral culture: Viral culture is used to determine whether a sample containing virus is capable of replication. Replication is a surrogate measure for inducing infection. Other methods to detect virus in a sample such as PCR cannot determine the viability of the organism in the sample. A sample is applied to a susceptible culture of cells and incubated up to a few weeks to detect morphological changes such as plaques that would indicate the presence of a viable virus.

Appendix Resources 1. National Institute for Occupational Safety and Health (NIOSH). Workplace safety and health topics: aerosols [Internet]. Atlanta, GA: Centers for Disease Control and Prevention; 2010 [cited 2020 Mar 18]. Available from: www.cdc.gov/niosh/topics/aerosols/

  1. Expert Panel on Influenza and Personal Protective Respiratory Equipment. Influenza transmission and the role of personal protective respiratory equipment: an assessment of the evidence. Ottawa, ON: Council of Canadian Academies; 2007. Available from: https://ccareports.ca/wp-content/uploads/2018/10/2007-12-19_influenza_ppre_final_report.pdf
  2. Health Protection Scotland, Infection Control Team. Aerosol generating procedures (AGPs) [Internet]. Version 1.4. Glasgow: Health Protection Scotland; 2020 [cited 2020 Jul 15]. Available from: https://hpspubsrepo.blob.core.windows.net/hps-website/nss/2893/documents/1_tbplr-agp.pdf
  3. Health Canada. Infection control guidelines: hand washing, cleaning, disinfection and sterilization in health care. Can Commun Dis Rep. 1998;24(Suppl 8):1-55. Available from: http://publications.gc.ca/collections/collection_2016/aspc-phac/HP3-1-24-S8-eng.pdf

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Citation: Ontario Agency for Health Protection and Promotion (Public Health Ontario). COVID-19 – What we know so far about… routes of transmission. Toronto, ON: Queen’s Printer for Ontario; 2020.

Source: Public Health Ontario. For more information about PHO, visit publichealthontario.ca.

Disclaimer This document was developed by Public Health Ontario (PHO). PHO provides scientific and technical advice to Ontario’s government, public health organizations and health care providers. PHO’s work is guided by the current best available evidence at the time of publication.