Cats probably transmit COVID-19 efficiently, but dogs less efficiently. 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.). 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 (Halfmann et al.; Shi et al.). Since stray cats typically interact minimally and indirectly with humans, this shows how transmissible this virus is. 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.
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. 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, Li, 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.).
Laboratory experiments found that SARS-CoV-2 lasts for 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, and cultured the viruses in cells to find if the viruses were still viable, a more thorough method than using PCR to find viral RNA. 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 is generally less stable on surfaces at higher temperatures and humidity, but other factors probably more determine transmission (Chin et al., National Academies of Science “SARS-CoV-2 survival…”). 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.).
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.). 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…”).
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 (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…”; Food and Drug Administration; Herbst; Parker-Pope; Stump and Nguyen).
No reports were found of SARS-CoV-2 transmitted via food by itself. Viral RNA was found in people’s gastrointestinal systems, showing potential of oral-fecal transmission (Gu et al.; Wong et al.; Yeo et al.). 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).