How another COVID-style pandemic could be triggered by rats

By Mark Waghorn via SWNS

Another Covid-style pandemic could be triggered...by RATS, warns new research.

The rodents - notorious for spreading bubonic plague - are symptomless carriers of coronaviruses.

They have evolved resistance to the pathogens from repeated ancestral infections.

Lead author Professor Mona Singh, of Princeton University, New Jersey, said: "This raises the possibility that modern rodents may be reservoirs of SARS-like viruses."

The study in PLOS Computational Biology also applies to mice, warn the US team.

SARS-CoV-2, the virus that causes Covid, is of zoonotic origin - meaning it jumped from an animal to humans.

Horseshoe bats in China are suspected of passing it on to an intermediary species - possibly pangolins.

The flying mammals harbor numerous SARS-like viruses without getting ill.

Identifying other creatures that have adapted tolerance mechanisms to coronaviruses is important.

They are potential viral reservoirs that can spread new pathogens to humans.

Pandemics are being fuelled by globalization, urbanization, climate change, increased human-animal contact and health worker shortages.

There have been three since 2000 - SARS (severe acute respiratory syndrome) in 2003, swine flu (H1N1) in 2009 and now Covid.

SARS spread from civet cats and bats in China and swine flu from an intensive pig farm in Mexico.

In between, there have been regional outbreaks of bird flu from poultry and MERS (Middle East respiratory syndrome) from camels.

There has also been Ebola from monkeys and pigs, Rift Valley fever from livestock, West Nile fever from birds, Zika from monkeys and Nipah from bats.

Prof Singh and graduate student Sean King performed an evolutionary analysis of the protein spikes used by SARS viruses to infect hosts.

Known as ACE2 receptors, they hook onto the cells of mammals - including humans - to gain entry.

Primates had highly conserved sequences of amino acids in the sites known to bind SARS viruses.

Rats and mice had a greater diversity - and an accelerated rate of evolution - in these spots.

Overall, the results showed SARS-like infections have not been evolutionary drivers in primate history.

But some rodent species have been exposed repeatedly - for a considerable evolutionary period.

Added Prof Singh: "Our study suggests ancestral rodents may have had repeated infections with SARS-like coronaviruses.

"They have acquired some form of tolerance or resistance to SARS-like coronaviruses as a result of these infections.

"This raises the tantalizing possibility some modern rodent species may be asymptomatic carriers of SARS-like coronaviruses - including those that may not have been discovered yet."

Earlier this year a study published by the UK's top scientific advisers SAGE, which has guided the Government through the Covid crisis, found coronaviruses could be transmitted by rats.

The DEFRA (Department for Environment, Food and Rural Affairs) researchers said the risk to most people is 'very low' unless they work near the animals.

They also reported rodents can catch the virus from people - particularly the Kent and South African strains which are more transmissible.

Rats could then pass Covid between themselves - and cause "sustained population level transmission" among the animals.

The rodents have long been blamed for spreading the Black Death around medieval Europe in the 14th century - killing tens of millions.