Study of pandemic triggers finds infection numbers, virus released in environment significant

New Delhi, Aug 22 (PTI) A study that looked at whether a virus can trigger a pandemic in a species not previously exposed to it has found that the fraction of the species population that gets infected and the virus' ability to multiply and release copies of itself into the environment could be particularly significant.

Among the multiple theories around how the COVID-19 pandemic got triggered is one that concerns a 'spillover' of the disease-causing virus from a bat to humans, via an intermediate species.

While a pandemic is extremely rare, spillover events happen all the time and therefore, the study's findings can help "figure out which outbreaks to worry about so that we can direct our public health resources where they need to go to prevent and respond to disease emergence," senior author David Kennedy, an associate professor of biology at The Pennsylvania State University in the US, said.

With the acute emergency of the COVID-19 pandemic well behind us, efforts around the world are underway to prevent the next one.

"Pandemic prevention efforts largely focus on identifying the next pandemic pathogen, but that's like finding a needle in the haystack," Kennedy said.

For the study, published in the journal PLOS Biology, the researchers induced a spillover among the 'Caenorhabditis' species of worms (hosts) by exposing them to 'Orsay', a virus (pathogen).

The worms were seen to reproduce and grow for five to 13 days, after which 20 adult worms were transferred to a new, virus-free Petri dish where they could multiply and grow again -- this was repeated until no trace of the virus could be detected in the worms.

Specific traits among worms remaining from the initial lot were studied for factors including what fraction of the worms were infected and how much virus each worm shed into the air.

"Our study demonstrates that early epidemiological characteristics can play a substantial role in explaining the ultimate outcome of a spillover event," the authors wrote.

"Infection prevalence and shedding (of virus material in the air) were significantly associated with virus maintenance," they said.

More than half the differences seen in the amounts of virus persisting in the worms could be linked to infection prevalence and virus shedding detected in the initial plate, the researchers said. Vulnerability of the host to the virus was also found to be an important factor.

"That means these early traits can actually tell us quite a bit about what's going to happen way off in the future," Kennedy said.

The researchers also found infection intensity -- or severity of infection -- did not predict virus persistence and spreading in the population. PTI KRS RHL