City rats don’t seem to harbor viruses that infect more people than their rural cousins, study finds

“Dirty” urban animals like rats may be notorious for harboring infectious diseases, but new research shows these urbanites no longer carry human-infected viruses any more than their rural types.

The scientists say urban species suffer from “sampling bias” when prosecuted for infectious viruses, so their reputations as disease carriers are likely disproportionate.

According to experts, nature in the city may pose less of a threat to future pandemics than previously thought.

Mice carried the famous fleas that caused the Black Death, a devastating bubonic plague epidemic in the 14th century, and this may explain their notorious reputation that continues to this day.

The new study was led by an international research group led by scientists from Georgetown University, Washington DC and published in Natural Ecology and Evolution.

The study compared mammal species (such as rat, fox, badger and raccoon) that were adapted to urban areas with those that could not live in urban environments (such as deer, weasels and otters).

“There are many reasons to expect urban animals to develop more diseases, from their food to their immune systems to their proximity to humans,” said study author Greg Albery of the Georgetown University School of Arts and Sciences.

“We found that urban species actually harbored more diseases than non-urban species, but the reasons for this seem to be largely related to the way we study disease ecology.

“We looked more at animals in our cities, so we found more parasites and we started cutting crops.”

Scientists have long suspected that cities could be hotspots for epidemic risks, thanks to species like mice, foxes and pigeons.

The Covid pandemic has aroused great interest when the risk of future viral outbreaks, not only of SARS-CoV-2 (the virus that causes Covid), but also of other viruses, is highest.

A growing mouse problem in Washington DC caused two people to be infected with a respiratory virus called Seoul hantavirus in 2018, according to the Centers for Disease Control and Prevention.

For the new study, the researchers tried to figure out whether animals adapted to living in cities often carry different viruses.

After examining the pathogens harbored by nearly 3,000 mammalian species, they found that animals adapted to cities can harbor about 10 times more types of disease than species that cannot live in urban environments.

However, they found that the model was partially a problem of sampling bias; Species that adapt to the urban environment are nearly 100 times better studied in the scientific literature.

Scientists have long suspected that cities could be hotspots for epidemic risks, thanks to species such as mice, foxes and birds.

Surprisingly, after adjusting for the sampling bias, the team found that species living in urban areas were not more likely to harbor human infectious viruses.

“It’s surprising that more than 100 times more studies have been published on them, even though species adapted to urban areas have 10 times more parasites,” said Albery.

“If you correct this bias, there are no more human pathogens than expected, meaning that our perception of new disease risks was overblown by our sampling process.”

While the findings don’t mean cities are disease-free, they could “cleanse” urban animals from their reputation as “hyper reservoirs” of infectious disease.

“This probably means that urban animals aren’t hiding as important new pathogens as we thought, pathogens that could cause the next ‘disease X,'” Albery said.

But they are extremely important vectors of many pathogens that we still know.

“Rats, raccoons and rabbits can still coexist with us and spread many diseases among people who still live in urban areas.”

The authors say that future research should examine how urban living may affect disease prevalence and transmission.

Almost all disease data in the study came from the United States and Europe, so further studies can expand the data to global samples.

As for Covid, it is believed that the risk of humans spreading SARS-CoV-2 (the virus that causes Covid) to animals is greater than any other route.

Bubonic plague is a type of infection caused by the bacteria Yersinia pestis, which is mainly spread to rodents by fleas. The picture shows people infected during the bubonic plague epidemic of the 14th century.

According to the U.S. Centers for Disease Control and Prevention, animals have a “low” risk of transmitting SARS-CoV-2 to humans.

In rural Ohio, it emerged in December that white-tailed deer were infected with SARS-CoV-2, possibly due to human transmission.

There is currently evidence that SARS-CoV-2 originated in horseshoe bats, although the virus was transmitted to humans through pangolins, a scaly mammal often mistaken for a reptile.