Beware Influenza, The Silent Killer

It is likely that within the next few weeks, the number of infections with influenza virus will spike in much of the country. Flu cases typically peak in February and can last into May. As of December 26, the CDC reported“elevated” outpatient flu-like illnesses in most of the nation’s surveillance regions.

The “flu,” which is marked by high fever, muscle aches, malaise, cough and sore throat, is transmissible through airborne droplets and is so infectious that after an airplane sat for three hours with its engines off and no air circulating, within three days, 39 of the 54 people on boardcontracted the flu, infected by a single passenger.

And it’s a killer: The “Spanish flu” pandemic of 1918-19 caused the deaths of 583,135 Americans, according to public health authorities at the time. Although we no longer experience mortality on the scale of Spanish flu, during a non-pandemic season on average the virus still kills thousands each year in this country. From the 1976-77 season to the 2006-07 season, flu-associated deaths in this country ranged from a low of about 3,000 to a high of about 49,000, according to the Centers for Disease Control and Prevention.  (Worldwide, flu kills about 250,000-500,000 annually.)

Vaccination is the key to prevention, but the science surrounding flu vaccines is anything but straightforward. Last year’s vaccine, for example, was poorly effective against the predominant flu variant that was circulating; it reduced a vaccinated person’s risk of seeking medical attention by only 23 percent among people of all ages. (Within population subgroups, vaccines’ effectiveness varies widely because it is affected by various factors, including the general health and age of the recipient; for example, they are much less effective in the elderly.)

Two recent studies published in the Journal of Infectious Diseasesfurther complicate the picture: The use of statin drugs (a group that includes highly prescribed medications such as Lipitor, Crestor and Zocor), which is especially common in the elderly to control elevated blood lipids, seems to blunt the immune response to flu vaccination.