The new virus directory shows which viruses are the most dangerous

In a typical year, scientists get two or three viruses which has not been seen in humans before. The number changes, but the trend has been consistent since the 1960s.

Most of these viruses attract little attention, and my colleagues and I often search through old medical papers to find any mention. Other viruses end completely and all forgotten. On the other hand, the discovery of HIV-1 in 1983 and Sars-CoV-2 in 2020 heralded the epidemics of AIDS and COVID, respectively. They are all dead tens of millions.

The next time a scientist discovers a strange or unknown virus in a patient—perhaps in the next few months—how will they know if it could cause a public emergency on the same scale as AIDS or COVID? My team at the University of Edinburgh have been using studies on the history of viruses help answer this question.

Epidemics come in many forms, but recently the most common ones are viruses with genomes made from RNA (instead of the usual DNA). Many types of RNA viruses have existed to be knownand there may be millionsbut only 239 are the ones that infect people. We soon published a catalog which helps to determine which ones are the most dangerous.

Color and severity of disease are important indicators, but there will be no epidemic unless the virus spreads among people. This can include contact with, or breathing in, or contact with blood or feces, or being bitten by a mosquito or tick.

For two-thirds of the viruses on our list, an infected person will not spread their disease. These are known as zoonotic viruses, meaning that people usually catch them from animals rather than other people. Rabies is one example.

This sounds promising, but viruses change rapidly and there is a reasonable concern that a zoonotic virus could spread between humans. That’s why scientists are so worried bird flu. But there is no documented example of an RNA virus doing this. Rabies does not exist, although it does exist tens of thousands of civil cases every year.

The biggest threat comes from viruses that can spread from person to person. It can be very contagious – as did the series of Types of SARS-CoV-2—but crossed from animals capable of spreading among humans. Long ago, it was the source of measles, mumps, and rubella, as well as many viruses associated with the common cold and stomach flu.

Then there are viruses that can spread between humans but, so far, have only caused a few epidemics. It’s because of them R number (how many people, on average, one person gets infected with) are very low and disease chains die out of their own accord. But R numbers can change; for example, when a virus that lives in remote villages reaches the city. It happened with Zaire ebolavirus in West Africa in 2014.

There have been only twelve names our list the spread of the virus, but it is an indication of an emergency. Zaire ebolavirus, chikungunya transmitted by insects, Zika and Oropouche viruses, and mpox (a DNA virus) were the first to enter, and all have gone on to cause major epidemics.

Some of the rarer viruses on our list have also been identified. One is the Andes hantavirus, which causes the latest an explosion on a ship. Another is the Bundibugyo ebolavirus, which is currently available widespread in Central Africa.

The next epidemic is HIV

Our findings may also help predict what future pandemics will be called disease X– it may look like. COVID is a good example.

In 2019, my team showed that highly contagious viruses are closely related to other viruses that circulate among humans, but they emerge differently from animals. This turned out to be the best explanation for SARS-CoV-2, very similar to the original SARS coronavirus but independently (and perhaps in a different way) taken from bats.

Last year, the World Health Organization said provided a SARS-like coronavirus as a candidate for disease X. That’s why scientists were afraid of COVID from the beginning—it’s what they’re looking for.

In contrast, neither the Andean nor the Bundibugyo virus has a reputation for causing a global epidemic. But if it was, for example, a a novel virus associated with measles then that would be another story. In this situation, there may be a more real possibility of a global emergency than COVID.

Andes and Bundibugyo strengthen one important lessonthough: They were all spread out for weeks before they were picked up. So is COVID. Finding and understanding new viruses quickly they can prevent the next epidemic from starting again, and it can make a huge difference in the loss of lives and livelihoods.

Mark Woolhouse and professor of infectious disease epidemiology at University of Edinburgh.

This article was reprinted from Discussion under a Creative Commons license. Read the book the first story.