A simple math problem lies at the heart of a heated debate over whether scientists should be allowed to publish provocative research into the transmissibility of H5N1 flu. Assuming the avian virus could spread easily among people, just how deadly would an H5N1 pandemic be for humans?
Flu scientists tend to shy away from that question, suggesting that it is not possible to predict how lethal the virus would still be after undergoing the necessary changes to adapt to human physiology. But inevitably, people look for clues to what appears to be the best predictor of the virus's future path—its current behavior. And that appears downright terrifying: as many as 59 percent of people known to have contracted the virus have died from the infection.
More specifically, of the 584 people who have tested positive with what the World Health Organization (WHO) confirms is H5N1, 345 have died. (These numbers are current as of February 8, 2012.)
But what if H5N1 isn't as deadly as the official numbers suggest?
Indeed, two researchers have charged into the already fraught H5N1 publication controversy insisting the numbers are wrong, that the true mortality rate is likely to be much, much lower and that bad policy is being driven by the inflated figures.
Peter Palese, a noted influenza virologist at Mount Sinai School of Medicine in New York City, and Vincent Racaniello, a professor of microbiology at Columbia University Medical Center, also in New York City, are among a vocal group of scientists who vehemently oppose any decision to suppress the details of research conducted by Yoshihiro Kawaoka of the University of Wisconsin–Madison and Ron Fouchier of Erasmus Medical Center in the Netherlands.
Fouchier and Kawaoka had—at the request of the National Institutes of Health—figured out whether the H5N1 virus could become more transmissible in non-avian species. Their efforts reportedly revealed that just a few mutations were all that was needed to create a bird flu virus that is easily transmitted between ferrets. In addition, Fouchier said that his strain remained just as deadly to ferrets as it had been to birds, although Kawaoka later declared that his lab strain was not lethal.
Palese suggested in a perspective article co-authored by Taia Wang and published ahead of print on January 25, 2012 in Proceedings of the National Academy of Sciences that the case fatality rate of H5N1 human was almost certainly "orders of magnitude" too high.
Starting with the current 59 percent rate, if you start pushing the decimal point left, 59 becomes 5.9, which becomes 0.59 or even 0.059. Each adjustment of the decimal corresponds to an order of magnitude. (For comparison's sake, the mortality rate of current seasonal flu is less than 0.1 percent whereas researchers estimate that the mortality rate of the killer 1918 flu pandemic was around 2 percent.)
Racaniello, who did his thesis research under Palese, suggested on his popular Virology Blog in early January that the estimates of H5N1's killing potential were vastly overrated. Citing a recently published study that found what might be H5N1 antibodies in the blood of some villagers in Thailand, he mused that if 9 percent of rural Asians had antibodies to the virus, the perception of how dangerous H5N1 is would change dramatically.
In the flu world, few people would argue that Palese and Racaniello are wrong that the case/fatality rate is too high. It might be difficult, though, to find many who agreed with their conclusion on what that means about the virus.