Other Routes

Household Animals

[Date of latest publication cited: November 18, 2020]

Cats have moderate risk of COVID-19 transmission, dogs a low risk, and rodents have high to low risk, because of the degree of similarity of their angiotensin converting enzyme 2 (ACE2), the chemical on the outside of cells that SARS-CoV-2 attaches to (Damas et al.; Howard).    Experiments found that cats can be infected with SARS-CoV-2 by intranasal inoculation and by staying near an infected cat, indicating respiratory droplet transmission (Gaudreault et al.Halfmann et al.; Kansas State University; Shi et al.).  Both stray and domestic cats in Wuhan had antibodies to SARS-CoV-2 after the epidemic started, but not before, perhaps indicating infection from humans (Zhang Q, Zhang H, et al.).  Since stray cats typically interact minimally and indirectly with humans, this shows how transmissible this virus is.  Cats and humans can transmit SARS-C0V-2 to each other.

Similar experiments with intranasal inoculation found dogs transmitted less efficiently than cats (Shi et al.).  A Hong Kong dog and a US dog were infected, perhaps by their owners (Office International des Épizooties; WRAL).  Two cats in New York state were found infected (Centers for Disease Control and Prevention “Confirmation…”; Peltz).  These studies indicate that household mammals could function as a vector and reservoir of SARS-CoV-2.   Cats can also get infected with feline coronavirus (FCoV, FECOV, or FECV), which has structures and functions partly similar and partly different from SARS-CoV-2 (Acheson; Ryu).  So if a cat had FECOV, that probably did not cause immunity to SARS-CoV-2.

The US CDC recommends that if people and animals live together, both animals and people should similarly take precautions and seek treatment (Centers for Disease Control and Prevention, “Confirmation” “If you have pets…”, “COVID-19.and Animals..”):

Do not let pets interact with people or other animals outside the household.

Keep cats indoors when possible to prevent them from interacting with other animals or people.

Walk dogs on a leash, maintaining at least 6 feet from other people and animals.

Avoid dog parks or public places where a large number of people and dogs gather.

If  a person or animal is sick with COVID-19 (either suspected or confirmed by a test), restrict contact and stay isolated from  other people and animals.

If a person or animal goes to a doctor, nurse, veterinarian, etc., tell the health professional about any exposed or sick people or animals in your home.


Fomite Surfaces

[Date of latest publication cited: November 18, 2020]

Fomite surfaces are also one of the main ways COVID-19 spreads (Lee E, Wada, et al.). Scientists using PCR found SARS-CoV-2 RNA in many places near infected people.  In a Nebraska hospital, 65% – 82% of room surfaces, personal items, and toilets had SARS-CoV-2 RNA (Santarpia et al.).  In hospitals in Wuhan, scientists found SARS-CoV-2 RNA on many surfaces in patient areas, ICUs, medical staff areas, and public areas.  They suspected that when patients coughed and breathed, the virus-laden droplets and aerosols deposited on surfaces (Guo et al.; Liu Y, Ning, et al.).  Patients who exhaled millions of SARS-CoV-2 viruses into the air also left SARS-CoV-2 on some, but not all of, the surfaces around them (Ma et al).

Scientists also suspected that viruses moved from surfaces to the air, when people disturbed virus-laden droplet deposits on surfaces (Guo et al.; Liu Y, Ning, et al.).  Surfaces had viral RNA even in the rooms used by a patient with only mild upper respiratory symptoms, in rooms without viral RNA in the air (Ong et al.), and rooms with asymptomatic infected people (Wei L, Lin, et al.).  Hands touching these virus-laden surfaces could transfer viruses to nose, eyes, or mouth (Brosseau).

On one of the cruise ships having many infected passengers, scientists found SARS-CoV-2 RNA on many surfaces in rooms of both asymptomatic and symptomatic infected passengers 17 days after the passengers left.  This shows that the viral RNA can remain there that long, maybe longer, but does not prove that this caused transmission (Moriarty et al.).

It would be difficult to prove or disprove if people could get SARS-CoV-2 from fomites.  Two people were infected, perhaps via fomites, on air flights closely studied by the Korean Centers for Disease Control (Bae, Shin, et al.).

Experiments found that guinea pig hair can transmit influenza to other guinea pigs, and rubbing tissue paper can disperse influenza viruses into the air, called “aerosolized fomites.”  So, perhaps SAR-CoV-2 could be spread this way (Asadi, Gaaloul ben Hnia; Robinson)

Laboratory experiments found that SARS-CoV-2 remains viable for 28 days on smooth surfaces at 20 degrees Celsius (68 degrees Fahrenheit), but they did not test longer than 28 days.  They cultured the viruses in cells to test viability, a more thorough method than using PCR to find viral RNA (Riddell et al.).  Another showed it lasting 3 hours to 7 days on different materials, but none tested them for longer than 7 days.  One research team spread viable SARS-CoV-2 viruses on surfaces, took samples from the surfaces after different time lengths, found them viable.  After 72 hours, the viruses were still viable on plastic and stainless steel, implying they might last longer. On cardboard, no viruses lasted longer than 24 hours, and some were not viable in even less time.  On copper, no viruses lasted longer than 4 hours (National Institutes of Allergies and Infectious Diseases; van Doremalen et al.).  Another set of experiments found SARS-CoV-2 lasted up to 3 hours on tissue and printing papers, 2 days on wood and cloth, 4 days on banknotes and glass, and 7 days on surgical masks, plastic, and stainless steel (Chin et al.).  Another study found it remained stable and could be cultured in cells after at least 7 days on smooth surfaces, 3-4 days in urine, and several hours in human feces (Liu Y, Li T, et al.; Thomas).  SARS-CoV-2 with protein on surfaces decreased little, but decreased greatly without protein.  This shows that these viruses in mucous and saliva droplets and aerosols on surfaces can last long and contribute to transmission (Pastorino et al.).

SARS-CoV-2 disintegrates more rapidly on surfaces at higher temperatures (Magurano et al.) and humidity, but other factors probably more determine transmission (Chin et al., National Academies of Science “SARS-CoV-2 survival…”).

This new coronavirus SARS-CoV-2 is about as stable on surfaces as the 2003 SARS-CoV virus (Bai et al.; van Doremalen et al.; Zou et al.).  A review of similar betacoronaviruses (SARS and MERS) and less similar alphacoronaviruses (HCoV, a cause of the common cold) found they can last 9 days (Kampf et al.).  But the new virus is spreading to more people than SARS, probably because it creates more viruses inside infected people, and can transmit more from asymptomatic infected people to others (van Doremalen et al.).

In hospitals with many COVID-19 patients, cleaning removed viruses from surfaces.  In the Nebraska hospital described above, staff used powered air purifying respirators, N95 filtering facepiece respirators, and other personal protective equipment, and no staff were infected (Santarpia et al.).  In Wuhan hospitals, scientists and medical staff found SARS-CoV-2 RNA on surfaces, cleaned them and their hands, sampled the surfaces again, and found no SARS-CoV-2 RNA.  This shows that hand, face, and surface hygiene could probably stop transmission (Ong et al.).

Many commercially available disinfectants and hand sanitizers can clean and inactivate this novel coronavirus SARS-CoV-2 (Center for Biocide Chemistries; Chin et al.; Kratzel et al.).  Early in the pandemic, the EPA made a list of 431 products they thought probably disinfected SARS-CoV-2 because they were effective against other hard-to-destroy viruses with lipid envelopes (like coronaviruses) and protein capsids (like rhinoviruses and noroviruses).  Most of them contain as active ingredients quaternary ammonium compounds (QAC), hydrogen peroxide, sodium hypochlorite (bleach), ethanol (ethyl alcohol), or isopropanol (isopropyl alcohol) (Environmental Protection Agency “List N”).  Later experiments found that two Lysol sprays disinfected specifically SARS-CoV-2 (Environmental Protection Agency “EPA Approves…”).  Other coronaviruses infecting humans, including SARS, MERS, and HCoV (a cause of the common cold) can be disinfected by 62%–71% ethanol (such as alcohol gel), 0.5% hydrogen peroxide or 0.1% sodium hypochlorite (bleach) (Kampf et al.).  CDC recommended how to clean surfaces and disinfect SARS-CoV-2 (Centers for Disease Control “Cleaning…”).   Ordinary soap and water also destroy SARS-CoV-2 and disinfect hands and other surfaces (Chin, Poon; Dehbandi, Zazouli; World Health Organization “Water, sanitation, hygiene”).

Disinfecting surfaces reduced coronaviruses in the air.  In Wuhan hospitals, scientists and medical staff found SARS-CoV-2 RNA in the air.  Then they cleaned the surfaces, wore more personal protective equipment (PPE), and separated severe patients from moderately symptomatic patients in different wards or buildings.  Then they sampled the air again, and found less airborne SARS-CoV-2 RNA, which shows that these actions might prevent aerosol transmission (Liu Y, Ning, et al.).

Disinfecting surfaces probably also reduced infections in households.  A retrospective study found that households that had one infected person, and disinfected the home, transmitted to fewer other people in the household than households that id not disinfect (Wang Y, Tian, et al.)

Because of the many ways SARS-CoV-2 can stay on surfaces, if we are caring for a COVID-19 patient, we should wear a mask, and perhaps a clear face shield, not touch many surfaces in the patient’s room, wash our hands after each interaction with the patient, and wash or change clothes and shower after every few interactions with the patient.  But if we go out in public or to a store with no known infected people, then we do not need to do all those precautions each time.  We should, however wash hands after going out, and wipe packages (Centers for Disease Control and Prevention “Households…”; Desai, Aronoff “Food Safety and COVID-19”; Food and Drug Administration; Herbst; Parker-Pope “Is the virus on my clothes?”; Stump and Nguyen).

Other experts believe that only a small portion of infected people got this virus from fomite surfaces (Ma et al.).  Some suggest that people should put more effort into preventing other transmission modes, especially aerosols and droplets (Centers for Disease Control “CDC Updates”; Goldman; Ives, Mandavilli; Larsen; The Lancet Respiratory Medicine; Thompson).



[Date of latest publication cited: August 14, 2020]

No reports were found of SARS-CoV-2 transmitted by eating food (Desai, Aronoff “Food Safety and COVID-19”; International Commission on Microbiological Specifications for Foods; Whitworth) .  Viral RNA was found in people’s gastrointestinal systems, showing potential of oral-fecal transmission (Gu et al.; Wong et al.; Yeo et al.).  Inspectors found SARS-CoV-2 on one batch of chicken meat, but not on people who transported it (Wu, “You probably won’t catch coronavirus from frozen food”).   If SARS-CoV-2 is on food surfaces, and one touched it, it could be transmitted as on any fomite surface (Food and Drug Administration). Some physicians asked the US Department of Agriculture to warn consumers about potential transmission via food (Physicians’ Committee).