Scientists say there are approximately 320,000 viruses present in mammals that are yet to be discovered, according to a study published in the journal mBio.

Researchers from the Center for Infection and Immunity (CII) at Columbia University’s Mailman School of Public Health and EcoHealth Alliance say that uncovering the majority of these viruses could be critical for early detection and developing cures for disease outbreak in humans.

Around 70% of emerging viral diseases, including HIV/AIDS, Ebola, West Nile, Influenza and SARS (sever acute respiratory syndrome) are a result of infections from animals (zoonoses) that have spread across to the human race.

According to the World Health Organization, although zoonoses have been recognized for many centuries, only 200 have so far been identified.

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Researchers studied the flying fox bat – the known source of many Nipah virus outbreaks – in Bangladesh.

For the study, the researchers began researching a bat called the “flying fox” in the jungles of Bangladesh. The bats are known to be the source of several outbreaks of Nipah virus, and the research team took 1,897 biological samples from them.

Polymerase chain reaction was used to identify 55 viruses over nine viral families. Of these, the researchers say that only five viruses were previously known – two human bocavirues, an avian adenovirus, a human/bovine betacoronavirus and an avian gammacoronavirus.

Of the 50 viruses that were newly discovered, 10 were in the Nipah virus family.

The researchers then used a statistical technique to estimate the presence of three other rare viruses that were unaccounted for in the bat samples, taking the number of viruses to 58. This number was then applied to all 5,486 known mammals, reaching a total of 320,000 undiscovered viruses.

Peter Daszak, president of EcoHealth Alliance and study author, says:

For decades, we have faced the threat of future pandemics without knowing how many viruses are lurking in the environment, in wildlife, waiting to emerge.

Finally we have a breakthrough. There are not millions of unknown virus, just a few hundred thousand, and given the technology we have it is possible that in my lifetime, we will know the identity of every unknown virus on the planet.”

The study authors say that the cost to discover the viruses in all mammals would equate to approximately $6.3 billion. But they compare this figure to the cost of the economic impact the SARS pandemic caused.

“By contrast, the economic impact of the SARS pandemic is calculated to be $16 billion,” says Simon Anthony, a scientist at the CII and lead author of the study.

“We are not saying that this undertaking would prevent another outbreak like SARS. Nonetheless, what we learn from exploring global viral diversity could mitigate outbreaks by facilitating better surveillance and rapid diagnostic testing.”

“If we know what is out there,” he adds, “we’ll be a lot better prepared when a virus jumps over into a human population.”

The researchers say that the figure of 320,000 undiscovered viruses is just an estimate and that the number is likely to be higher after accounting for additional viral families, and after using more detailed sequencing methods created at the CII.

They also note that the viruses discovered in the flying fox in Bangladesh may not be representative of all flying foxes across Southern Asia. Also, they do no know whether all mammals will hold a similar number of viruses, and to what extent these can be shared between species.

However, they add that two follow-up studies are planned in order to reach a more accurate figure and to determine the diversity of the viruses.

“To quote Benjamin Franklin, an ounce of prevention is worth a pound of cure,” says W. Ian Lipkin, director of CII and senior study author.

Lipkin adds:

Our goal is to provide the viral intelligence needed for the global public health community to anticipate and respond to the continuous challenge of emerging infectious diseases.”

Recent studies have shown the continued discovery of human viruses that may have stemmed from animals. Separate research from Columbia University suggested that MERS (Middle East respiratory syndrome) may have begun in bats from Saudi Arabia.

Another study from the University of Edinburgh in Scotland suggest that the MRSA infection can be traced back to cattle.