Scientists at the National Institutes of Health believe they’ve discovered the reason why flu virus is more infectious in cold winter temperatures:
In the current study, the NIH researchers used a sophisticated magnetic resonance technique, developed and previously tested in NIAAA’s Laboratory of Membrane Biochemistry and Biophysics, to create a detailed fingerprint of how the virus’s outer membrane responded to variations in temperature. The virus’s outer membrane is composed chiefly of molecules known as lipids, explained the study’s senior author, Joshua Zimmerberg, Ph.D., chief of NICHD’s Laboratory of Cellular And Molecular Biophysics. This family of molecules does not mix with water, and includes oils, fats, waxes, and cholesterol.
Dr. Zimmerberg and his colleagues found that at temperatures slightly above freezing, the virus’s lipid covering solidified into a gel. As temperatures approach 60 degrees Fahrenheit, the covering gradually thaws, eventually melting to a soupy mix.
Cooler temperatures, apparently, cause the virus to form the rubbery outer covering that can withstand travel from person to person, Dr. Zimmerberg said. Once in the respiratory tract, the warm temperature in the body causes the covering to melt to its liquid form, so that the virus can infect the cells of its new host, he added.
"Like an M&M in your mouth, the protective covering melts when it enters the respiratory tract," Dr. Zimmerberg said. "It’s only in this liquid phase that the virus is capable of entering a cell to infect it."
In spring and summer, however, the temperatures are too high to allow the viral membrane to enter its gel state. Dr. Zimmerberg said that at these temperatures, the individual flu viruses would dry out and weaken, and this would help to account for the ending of flu season.
The finding opens up new possibilities for research, Dr. Zimmerberg said. Strategies to disrupt the virus and prevent it from spreading could involve seeking ways to disrupt the virus’s lipid membrane.
Press release: NIH Scientists Offer Explanation for Winter Flu Season…
Image credit: Wellcome Images: TEM of Influenza A virus…