A. Recent human coronaviruses
Coronaviruses are enveloped viruses which can cause respiratory and enteric disease in both humans and animals. Bats appear to be the ultimate reservoir of several of the more recent coronavirus isolates, including;
- MERS-CoV – this virus causes the Middle East respiratory syndrome. The origins of the virus are not fully understood but, according to the analysis of different virus genomes, it is believed that it may have originated in bats and was transmitted to camels sometime in the distant past.
- SARS-CoV-1 – this virus is thought to be an animal reservoir, perhaps bats, that spread to other animals, including civet cats, and first infected humans in the Guangdong province of southern China in 2002.
- SARS-CoV-2 – this is the virus strain that causes the current coronavirus disease (COVID-19). It is believed to have zoonotic origins and has close genetic similarity to bat coronaviruses, suggesting it emerged from a bat virus.
B. Three modes of transmission
At the present time, it’s widely though that the SARS-CoV-2 virus can spread rapidly between humans via three routes, these being;
- Respiratory – this is by droplets when symptomatic people sneeze or cough, releasing large droplets of virus-laden mucus
- Aerosol - virus particles can be released in a range of sizes, and some are small enough to be considered aerosols or fine particles that can stay suspended in the air for hours. They can travel with air currents across tens of feet. One study has found that virus particles that were aerosolised can remain viable for up to 3 hours.
- Contact - viral particles are emitted from the respiratory tract of an infected person and land on a surface. Another person then touches that object, then touches their nose, mouth or eyes. The virus then enters into the body via the mucous membranes, infecting the second person. Smooth, non-porous surfaces seem to transmit these viruses better than porous materials, possibly because porous and fibrous materials absorb and trap the virus particles, making it harder to transfer from a simple touch. Since animal hair is porous and also fibrous, it’s very unlikely that you could contract COVID-19 by petting or playing with a pet.
Interestingly, some other human coronaviruses can survive for as long as 9 days on certain surface types, with length of persistence also being correlated to inoculum dose and ambient temperatures. Some virus survival times quoted are;
- Plastic – 72 hours
- Stainless steel – 72 hours
- Copper – 4 hours
- Cardboard – 24 hours
C. Domestic pets, SARS-CoV-2 and fomite transmission
Whilst the virus responsible for the COVID-19 pandemic may have originated from an animal source, there is currently no evidence that our family pets are able to infect others at home. One study published in the journal Science, concluded that cats can become infected with the virus, and can also pass it on to other cats, but it also concluded that it was unlikely to spread in dogs.
There are some reported cases of dogs and cats that have tested positive for SARS-CoV-2 on PCR and serology, but there is only limited evidence that cats will develop clinical signs and no evidence for dogs.
There is currently no evidence that inanimate objects associated with pets, such as collars, leads, food or water dishes, can carry fomites for SARS-CoV-2, but there is more concern that these animals can act as generators and transmitters of fomites contaminated with the SARS-CoV-2 virus, particularly if the pet belongs to someone ill with COVID-19.
Whilst the measurable risks regarding pet-to-human transmission may be low, this may change as more information is gathered and our understanding of the virus improves.
D. Veterinary recommendations for owners with Covid-19
Veterinary experts from all around the world have formulated some recommendations and guidelines to make sure people and their pets remain safe during this pandemic. As a result, it’s generally advised that people who are sick with COVID-19 avoid contact with pets.
Despite the fact that the evidence of fomite transmission from pets is not currently available, there are some practical things we can do to minimise the risks. Some of this advice includes;
- Maintain separation - if owner becomes ill with COVID-19, it would be wise to try to ensure safe separation between themselves and their pet. This might involve asking one of their friends or family to take care of the animal.
- Suitable protection – in the event that an owner must care for their pet while ill, they could reduce the chance of spreading virus particles to their pet by;
- Using a face mask
- Ensuring their hands are washed before and after contact
- Avoid hugging and kissing their pet
- Stop their pet from licking them
- Resist the temptation to let their pet sleep on their bed
- Ensure no food utensils are shared
- Keep their pet inside to minimise the contact with other animals and people. Be aware though that keeping a cat inside can be very stressful for the cat.
- Adhere to very good hygiene protocols in the home, including washing food and water bowls, toys and bedding regularly.
- Don’t interact with cats that are not their own.
- Bathing – whilst there is no evidence that this will help, it might be worth considering as we do know that coronaviruses are readily killed by many biocidal agents, including washing with soap and water.
E. Systematic Reviews for Animals & Food
To help the veterinary profession and other animal health workers remain updated with what is known about SARS-CoV-2 and domestic animals, an online rapid review of the literature has been conducted by the Systematic Reviews for Animals & Food organisation.
Access the latest information here.