Influenza virus survives in dry conditions

Portland, February 12: A latest study suggests that cold and dry air of winters can serve as a home to the influenza virus. Reanalysis of data collected in 2007 has shown that there is a bigger probability of the influenza virus surviving in low-humidity conditions.

The study findings also revealed that a humidifier might work in places where there are hazards of influenza-multiplication. These places could be ICUs or a home with an ailing child etc.

According to Shaman, whose study appears in this week’s Proceedings of the National Academy of Sciences, “It seems that the influenza virus’ ability to survive and be transmitted person-to-person is greatly affected by how dry or wet the air is.”

Shaman and Melvin Kohn of the Oregon Department of Health Services in Portland re-examined a study that was done in 2007. That study had revealed that greater humidity levels slowed down the spread of flu among guinea pigs. The researchers also gauged air dampness using relative humidity.

The data available was then converted from relative humidity to absolute humidity and it was discovered that the relationship between humidity and flu spread shot up.

Relative humidity is the ratio of the amount of water vapours present in the air at a particular temperature to the maximum amount that air can hold at that temperature. Relatively 50 percent humidity means that air is holding 50 percent of its total capacity of water vapours.

On the other hand, absolute humidity is the amount of water vapours present in a unit volume of air.

Shaman said, “Absolute humidity, for reasons that remain undetermined, is affecting how long the virus remains viable.” He further added, “It really explains why you have this pronounced seasonality in temperature regions.”

The researchers also analyzed records of 1940s regarding airborne flu virus survival. Here also, data on relative humidity was converted to absolute humidity. It was proved again that the link between humidity and flu-spread strengthened.

According to Michael Gardam, M.D., PhD, an infectious disease specialist with the University Health Network in Toronto and Ontario’s public health agency, “Based on the papers that have been done thus far, I wouldn’t run out and buy humidifiers, but I would definitely buy humidifiers to study humidifiers.”

Scientists now need to study further and check if humidity actually affects the spread of the flu among humans. More research needs to be done to determine as to why the flu virus survives in dry conditions.

“The best way to protect yourself against influenza is to get vaccinated,” suggested Anice Lowen, PhD, a researcher at the Mount Sinai School of Medicine in New York.