KeepHealthCare.ORG – Flu Virus Evolution Can Be Unexpectedly Slow and Inefficient
The latest flu season may be over, but for the experts tasked with keeping the public safe from health threats, the next flu is always just around the corner.
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A new study by University of Michigan researchers sheds light on how the influenza virus evolves in people, knowledge that may one day enable epidemiologists to forecast just how bad a seasonal flu will be and provide more lead time for vaccine development.
When a person becomes infected with the influenza virus, the virus will copy itself inside the cells of the body. Influenza, like other RNA viruses, mutates very rapidly, says Adam Lauring, M.D., Ph.D. , assistant professor in the U-M Department of Medicine, Division of Infectious Diseases and the Department of Microbiology & Immunology. Every time it copies its genome, it’s making a mistake or two. At a population level, this mutation eventually leads to the development of new strains of the flu virus and is why the composition of the flu vaccine must change every year.
To study this process, Lauring collaborated with Arnold Monto, M.D., and Emily Martin, Ph.D., MPH, of the U-M School of Public Health, using samples provided by families throughout southeastern Michigan. The samples are collected as part of a Centers for Disease Control and Prevention-funded program that monitors the spread of seasonal flu throughout the U.S. and the effectiveness of the flu vaccine.
When members of the participating families get sick, they are asked to take swabs from their noses and throats, put them in a vial and take them to Monto’s lab. The researchers can then test the samples to determine which virus that person has. They also collect other epidemiologic information, such as the person’s age and whether they were vaccinated or have flu antibodies.
For their work, published in the online journal eLife, Lauring and his graduate student JT McCrone used the same samples to study the viruses themselves.
“It’s often hard to study disease transmission in the real world. These samples are valuable because they come from a population where people are getting naturally infected with the flu and transmitting it to each other,” Lauring says.
Using samples from about 50 people who submitted two swabs over the course of several days, Lauring’s lab harnessed next-generation sequencing technology provided by the University’s Biomedical Research Core Facilities to sequence each virus’s genome an average of 10,000 times. From the resulting data, they determined the most common virus sequences each person had, and they found rarer mutations in some of the viruses.