Researchers from the University of Hong Kong (HKU) on Friday said they had found evidence, for the first time, that pet hamsters can contract Covid-19 and pass it to humans – which they said was a likely cause of an outbreak of the Delta variant in Hong Kong in January.
The HKU’s school of public health reached the conclusion after jointly conducting a study with the Agriculture, Fisheries and Conservation Department.
The research team said while there were reports of human-to-animal Covid transmissions, there had been no evidence in the past that infected animals – besides farmed mink – could infect humans and lead to further human-to-human transmission.
The findings have been published in the Lancet medical journal.
In January, authorities culled more than 2,000 hamsters and small mammals after a worker at a pet shop in Causeway Bay and a customer there came down with the Delta variant and some animals subsequently tested positive for the coronavirus.
The operation drew criticism from some quarters, including animal rights groups.
In their study, HKU researchers found that over half of 28 sampled hamsters from the pet shop and a related warehouse were infected with Covid.
Genome sequencing showed that the hamsters had been infected in mid-October outside Hong Kong, about three months before the January outbreak, researchers said.
They also said that the infected hamsters later passed the virus to people, leading to further transmission in the local community.
Professor Leo Poon, a lead researcher, said their study highlighted a public health concern.
He said if the coronavirus is allowed to circulate among hamsters for a long period, the virus might acquire additional mutations and change its biological features, including its ability to transmit, cause diseases and evade vaccine protection.
He added that there is a possibility that human beings might acquire a novel coronavirus variant from pet Syrian hamsters, which might impact existing anti-epidemic measures.
Professor Malik Peiris, another lead researcher, said similar events might occur in other places, without being recognised.
“Our findings highlight that infected hamsters may play a role in movement of viruses across national borders,” he said.
The team also said there might be other animal species that can cause similar transmissions, adding that systematic surveillance of the coronavirus is needed in both wild and domesticated animals.
But researchers also noted that they did not study all the hamsters in the pet shops and warehouse concerned, as well as those sold before the investigation.
They said their study might therefore underappreciate the virus diversity found in the affected hamsters.
“Although unlikely, the possibility of an undetected local chain of transmission of SARS-CoV-2 delta AY.127 leading to infection of hamsters in the warehouse cannot be excluded,” they added.