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Explained: What does Covid-19 in gorillas tell us?

Members of a gorilla troop have tested positive for Covid-19 at the San Diego Zoo in California. How did they contract the infection? What do we know about the virus spreading from humans to animals?

Members of the Gorilla Troop are seen in their habitat on Sunday, Jan. 10, 2021 at the San Diego Zoo Safari Park in Escondido, Calif. (AP)

Members of a gorilla troop have tested positive for Covid-19 at the San Diego Zoo in California, becoming the first captive primates to contract the infection in the US. While some gorillas at the zoo are showing mild symptoms, further studies will be needed to understand the precise effects of the virus on these primates.

At the moment, the US Centers for Disease Control and Prevention (CDC) and the United States Department of Agriculture (USDA) do not recommend the regular testing of animals.

How did the gorillas contract the infection?

The zoo initiated testing for the gorilla troops after two of them started coughing and showing mild symptoms of infection on January 6. After testing their fecal samples, some gorillas were found to be positive for SARS-CoV-2 on January 8.

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It is likely that the gorillas contracted the infection from an asymptomatic staff member. Even so, the zoo has said that while the infected gorillas have congestion and are coughing, they are “doing well” and are expected to recover soon.

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Which other animals have tested for Covid-19?

Since the Covid-19 outbreak began early last year, there have been several reports of animals contracting the infection. For instance, we know that domestic cats, lions and tigers can be infected with the virus. In November, after the Danish Public Health Authority (Statens Serum Institut) discovered the mutated version of coronavirus in mink, the government decided to cull all of the country’s over 17-million population of the animal to avoid a spillover of the variant from animals to humans.

Such new virus strains are of concern since one of the mink-associated variants, which was identified in some humans in Denmark was thought to have moderately decreased sensitivity to neutralising antibodies.


In December, research conducted at the Centre for Genomic Regulation (CRG), which is headquartered in Barcelona showed that felines are particularly susceptible to the virus because of their cellular structure.

In April, a Malayan tiger at New York’s Bronx Zoo tested positive for the virus and is believed to have contracted it from an asymptomatic zoo employee.

Another research published last year in the journal Proceedings of the National Academy of Sciences of the United States analysed the potential risk of infection in 410 species including fish, birds, amphibians, reptiles and mammals. The research found that several primate species faced the highest risk of infection from SARS-CoV-2. Some of these primate species are critically endangered species including the Western lowland gorilla and the Sumatran orangutan.


According to the World Organisation for Animal Health, experimental infection studies have shown that poultry and cattle are not susceptible to infection.

What do we know about the virus spreading from humans to animals?

While the virus was initially transmitted from an animal to a human, the current pandemic is being mainly sustained by human to human transmission of the virus.

The CDC has said that while the virus can be transmitted from people to animals, the risk of the infection spreading from animals to humans is low.

People with pets should treat them as human family members, the CDC has advised. This means that pets should not be allowed to interact with people from outside the household.


Since the start of the pandemic, a few pets including cats and dogs have been known to contract the virus, probably due to close contact with people who were Covid-19 positive. Further, there have been reports about two dogs in Hong Kong — a Pomeranian and a German shepherd — who tested positive for Covid-19. However, while the dogs tested positive, they did not show any symptoms.

First published on: 12-01-2021 at 04:48:43 pm
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