Mar 9, 2011 14:32 GMT  ·  By

Pandemic flu viruses are in the nasty habit of striking their human targets in two-step blows. Experts say that this is very likely to happen with the 2009 H1N1(swine) flu virus that affected the world.

Generally, flu viruses tend to hit once, subdue for a year or so, and then come to strike again in some mutated form, that is usually way nastier than the original, and also better equipped to kill people.

Such was for example the case in the fall of 1917, when the first form of Spanish influenza swept the globe. Some people died, but their were mostly seniors, whereas teens and children recovered quickly.

This was no longer the case in the summer of 1918, when the virus returned, wreaking havoc, and killing an estimated 50 million people. It is estimated that this represented 3 percent of the world's population at that time.

The same thing happened over and over again since that time, and so epidemiologists and microbiologists are now worried that the pattern will repeat itself from the swine flu as well.

This particular strain contains genes collected from humans, swine and birds, mixed in such a way that it can prove deadly to humans even in its first form. Experts are now expecting a mutated form, more adapted to killing those it infects.

According to specialists, the only reason the 2009 epidemic did not cause as many casualties as authorities expected was a fault in the organism itself. It was not too good at spreading itself, they say.

But a new study by researchers at the Massachusetts Institute of Technology (MIT) shows that all the virus needs to do is mutate a single gene to become more easily transmissible from person to person.

The group reported its findings in the March 2 issue of the journal PLoS One, which is edited by the Public Library of Science. They are primarily addressed to the UN World Health Organization (WHO).

The WHO is in charge of tracking the evolution of influenza strains from season to season, in areas of the globe where the virus can endure around the year. This mostly happens around the Equator.

“There is a constant need to monitor the evolution of these viruses,” says the director of the Harvard-MIT Division of Health Sciences and Technology, Ram Sasisekharan.

The expert is also the senior author of the new research, and the Edward Hood Taplin professor at the Division.

“These are exactly the types of mutations that we need to watch out for in order to safeguard humans from future disastrous flu pandemics,” concludes Baylor College of Medicine assistant professor of biochemistry Qinghua Wang.