RATS in NYC are harboring Covid, study shows – and experts fear it poses zoonotic threat to humans

Rats in New York City are harboring Covid, a study has warned — and scientists are concerned they could infect humans.

Researchers at the University of Missouri trapped 79 rats that emerged from the sewer system at parks in the city.

Tests showed that 13 of the rodents (16.5 percent) had antibodies against Covid, a sign of a previous infection. Four had evidence they were currently infected.

A separate test revealed that rats could be infected with the Alpha, Delta and Omicron Covid strains, showing the rodents can harbor many variants.

With eight million rats living in America’s largest city — or about one per resident — experts warned that they posed a serious ‘zoonotic disease spillover’ risk. When viruses jump between species it raises the risk that they will obtain significant mutations, that could make them more transmissible or deadly.

Dr Henry Wan, a microbiologist at the University of Missouri who led the research, said: ‘Our findings highlight the need for further monitoring of SARS-CoV-2 in rat populations for potential secondary zoonotic transmission to humans.

‘Overall, our work in this space shows that animals can play a role in pandemics that impacts humans.

‘It’s important that we continue to increase our understanding [of the risks posed] so that we can protect both human and animal health.’

Rats can be exposed to Covid when they come into contact with water also used by humans infected with the virus, which can happen in sewer systems.

The virus may then be able to infect the rats, because the rodents have similar receptors on their cells to those in humans.

Scientists fear that Covid may be able to move into another animal reservoir and then mutate into a more severe version before jumping back into humans.

Some experts argue that this was how the Omicron variant emerged, the currently dominant strain, when rats in South Africa’s water systems became infected.

In the study, published today in the journal mBio, scientists said they set rat traps in September and November 2021.

The traps were placed mostly in city parks in Brooklyn that were near wastewater systems. Some were also captured near buildings outside the park boundaries.

All rats caught were from the species called Norway rats, with the Latin name Rattus norvegicus.

Each had blood tests for antibodies against Covid, indicating an infection.  

All the rodents were tested for antibodies against Covid, which would indicate an infection. Thirteen tested positive.

Four rats tested positive for proteins from the virus, indicating that they currently had an infection. From each, a partial Covid genome was then recovered. 

The scientists also conducted a challenge study, where they exposed a different group of rats to the three main Covid variants — Alpha, Delta and Omicron.

Examination two to four days post-infection showed that each had led to an infection in the rats.

For Omicron, the scientists used the variant BA.5.5 — which was behind about one in ten infections at the turn of the year.

Scientists fear that the next major pandemic will come from a disease that spills over from animals into humans.

There are currently mounting fears that a strain of bird flu H5N1 could cross the divide from chickens into people.

This year 11-year-old Bean Narong became the first person to die after catching this type of bird flu at her impoverished village in Cambodia.

The World Health Organization has urged countries to keep an eye on the strain, amid reports it has also evolved to infect mink and sea lions — bringing it one step closer to humans.