Three-Fourths of Flu Infected Won’t Know It: Study

Nearly three fourths of all influenza infections each season are asymptomatic, according to a recent study.

The study, published as a comparative community analysis in The Lancet, looked into infection patterns and history of influenza infection for several seasons, including the 2009 non-seasonal H1N1 pandemic. Researchers determined that while 18 percent of the U.K. population is infected with influenza annually, only 23 percent of those infections actually show traditional signs of the flu, with only 17 percent needing medical attention.

The study, which analyzed the seasonal flu history of 5448 unvaccinated persons in England from 2006 to 2011, required participants to give blood samples before and after each influenza season. Weekly inquiries throughout each season also allowed researchers to determine if the participants were exhibiting the standard symptoms of an influenza infection.

Testing the blood of the participants at the end of each season allowed researchers to conclude that while a great many participants proved to have been infected each year, approximately 77 percent of them never displayed any symptoms of infection, proving to be asymptomatic. Whether or not the flu infections cause unusual adverse symptoms in any of these infected participants remained unclear.

What does this mean? The study concluded that the human body might be more capable at fighting off or at least quelling the influenza virus than what is commonly thought. Health organization in North America and Europe both push for vaccination for the seasonal influenza virus in order to help stifle the virus's spread, but it has been revealed by past studies of these same organizations that the influenza virus only proves effective at preventing an infection 50 to 60 percent of the time.

Still, according to commentary accompanying the study, these results were less so to undermine the necessity of vaccination and more so to encourage a better understanding the influenza virus and how it interacts with the human body.

The study was funded by the Medical Research Council and Wellcome Trust and published by The Lancet on March 17.