Infecting people with COVID can be done by hamsters. This is the conclusion of a new study. It was published in response to the announcement made in Hong Kong in January that three cases of COVID had been linked to hamsters kept in pet shops.

Although the discovery was made in a preprint study submitted to Lancet on Jan. 28, it has not been peer reviewed nor published. This study is in addition to other research that has shown SARS-CoV-2 transmission between minks and humans on Danish farms.

NPR's Leo Poon, professor of health at the University of Hong Kong, says it is not surprising that animals can become infected. He was shocked to find the virus spreading from an animal source to humans and causing human-to-human transmission.

In an email, he stated that the possibility of SARS-CoV-2 being transmitted from animal to human is a serious public health concern. We must make serious efforts to stop this transmission, and vice versa.

In Hong Kong, the sequence of infection began with a fully vaccinated employee at a pet shop who tested positive for COVID. Because of the low incidence of COVID in Hong Kong, health officials were shocked. They were stunned to discover that it was the delta variant. The other cases in Hong Kong were imported omicron variants, which were identified in November.

This particular delta variant had something else. Scientists had never seen this mutation in any other delta case.

Public health workers took blood samples and swabs from the animal store after the employee was confirmed positive. More than half the hamsters were positive for SARS-CoV-2.

It was from the Netherlands

They discovered that the virus was passed from hamsters brought from the Netherlands to others. The virus had also been transmitted to at least two other people, the employee and the customer who had stopped by the shop briefly. This meant that the mutated delta variant of the virus was suitable for human spread.

Researchers found that hamsters often transmitted the virus via direct contact or airborne transmission to other hamsters in experiments. It's possible that airborne transmission occurred in this case, given the short visit of the customer.

According to reports, this variant has spread to at least 50 others in Hong Kong.

Like the mink in Denmark and Hong Kong, at-risk hamsters were culled. In all, around 2,000 hamsters were sold between December 22-January 19. Officials were then able to test and euthanize them.

Stopping the spread

These decisions are complex and health officials make them based upon their goals and policies regarding disease transmission. Suresh Kuchipudi is a clinical professor of virology at Penn State. He also co-authored studies on SARS-CoV-2 and deer. He doesn't believe that culling all animals positive for the virus, particularly wildlife, is possible.

He says there are other methods to stop the spread of the virus, such as deploying coronavirus vaccinations for animals or isolating anyone who comes in contact with positive animals.

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The virus is also spreading to deer populations across the United States. Kuchipudi and other researchers have uploaded a new preprint study on February 7 showing the first ever omicron infection in white-tailed deer at Staten Island.

There is no evidence to suggest that deer-to people transmission has been documented.

Numerous cases have been reported of people passing the virus on to animals. Animals with COVID infection include ferrets (cats, dogs), racoon dogs and fruit bats as well as zoo animals such as lions, gorillas, pumas and tigers.

Scientists say that these cases were only discovered after scientists examined the animals. This virus could spread to other animals that aren’t being monitored or not at all.

Poon says that the hamster study highlights the need to pay attention to any spillback into humans. In an email, he stated that the possibility of SARS-CoV-2 being transmitted from animal to human is a serious public health concern. We must make serious efforts to stop this transmission, and vice versa.

Scientists are concerned that the virus could mutate between animals and humans, creating new strains that could escape vaccine protection. Animals could be a reservoir for the virus and spread it to others even if human cases are less controlled.

Hong Kong discovered the infected Hamsters because of this.

Researchers were able to identify the connection between hamster and human by having so few COVID cases in Hong Kong.

Poon says that in countries like the U.S. where the virus is rapidly spreading, it might be difficult to detect "spillback events".

He adds that this means we are probably under-counting animal transmittance around the globe.

For example, in New York City, a bizarre version of the virus was detected in the sewage over the past year. Researchers suspect that it may be spreading among rats and other animals. This variant has not been transmitted from one animal to another.

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Kuchipudi states, "We don’t know how much deer are suffering." Our understanding is still very incomplete. We may be unaware of another variant of virus evolution, and we might not know what it is.

The virus could spread from cats to deer, deer mice to other animals and back again, he said. Unfortunately, there is not enough monitoring to determine if and how this is happening.

Kuchipudi states that uncontrolled or unmonitored spreading of the virus in animal reservoirs and multiple hosts could lead to the virus evolving, which could result in new variants that could undermine current vaccines for humans.

One deer in the study had antibodies from an earlier infection with SARS/CoV-2. However, it tested positive for omicron. This shows that animals can get breakthrough infections just like humans, he states.

He says this has serious implications for the spread of the virus to animals and humans.

Michael Worobey, head of the University of Arizona's ecology and evolutionary biology department, says that having a large number of evolving viruses in your system can lead to problems. He didn't work with the deer or hamster studies.

He says, "It's potentially worrying that something could end-up in something like whitetails deer, evolve for, let’s say, 5-10 years in that population and then jump back in humans and have picked a bunch of mutations which allow for escape from immune responses or some degree of escape."

He is still most concerned about the human-to-human spread and evolution of the coronavirus. This is especially true when the virus can survive for several months in immune-compromised people. The virus is more likely to make humans sicker if it evolves in humans - mutations in deer or hamsters might not be as devastating.

Worobey states, "Let's be careful not to get too worried about animals." Each wave of COVID presents more chances for the virus in humans to evolve.

It would also make it less likely that animals will become infected if COVID spikes are stopped among people.