Fooled by the Flu,
But Still Fighting

We can be thankful that this year’s flu, while surprising in some respects, is nonetheless a garden-variety rather than pandemic strain.

By: Dr. David L. Katz*

Flu season is well under way with cases confirmed in 44 U.S. states. Unfortunately, this year’s vaccine is proving effective about 40 percent of the time, according to the CDC. How can a mindless virus outsmart the knowledgeable scientists who devised this year’s vaccine? And what options do we have to protect ourselves?

The influenza virus is subject to something called antigenic drift. Antigens are proteins on the surface of the virus that enable our immune systems to recognize it as foreign, and attack it. These antigens ‘drift’ each year, meaning they change slightly, which is why a new flu vaccine is required annually.

Because of the danger influenza poses -- each year 200,000 U.S. citizens are hospitalized for flu, and over 35,000 die of complications -- the CDC tracks it closely, and prepares a strain-specific vaccine annually. Each year’s flu strains tend to originate in the Far East, so scientists track the emergence of flu in China, and develop vaccines accordingly. Since flu viruses can continue to change while moving slowly westward, the antigens used for the vaccine and the antigens on the actual virus may not quite correspond -- which is what happened this year.

THE GOOD NEWS? Even with only partial correspondence between virus and vaccine, infection rates are reduced by 40 percent, which makes immunization worthwhile. Most years, however, the vaccine prevents up to 90 percent of flu cases. Scientists’ educated guesswork was wrong this year, consequently, both influenza A and B strains differ somewhat from the mix in the vaccine.

Since flu season is just now peaking, it’s too early to know if this year’s flu is more severe than usual. Relative to the total number of annual infections, most years the flu is only infrequently a deadly threat to the very young, the elderly, and those with prior lung disease. Some years, however, the disease is especially virulent, and poses a greater risk of serious complications -- and even death -- to vulnerable populations, and otherwise healthy adults.

Flu symptoms are a well-known constellation of misery including fever, headache, muscle aches, and cough. The severity of muscle pain, known medically as myalgia, and the prominence of fever tend to distinguish flu reliably from the colds that abound this time of year. For guidance on recognizing flu, see http://www.cdc.gov/flu/keyfacts.htm.

Should symptoms of flu emerge in your household -- regardless if you and your family were immunized -- contact your doctor. Doctors’ offices can judge the likelihood of flu based on your symptoms, and the reporting of flu from your area. Health departments, and the CDC, keep health care professionals up to date on confirmed flu cases.

If flu is suspected or confirmed in your household, there are medications that can be used to shorten the course of illness, and even prevent it in other family members. Tamiflu and Relenza are effective much of the time, although here, too, the wily flu bug may outwit us at times. Last year, only 1 percent of flu strains were resistant to these antiviral drugs; this year, it’s up to 5 percent.

Neither antigenic drift, nor the tendency to develop drug resistance, is the flu bug’s most worrisome behavior. Those laurels go to antigenic ‘shift,’ which refers to an abrupt, major change in flu surface proteins. Because the result is a flu strain our immune systems don’t recognize, sudden shifts in flu antigens presage flu pandemics. This is the process that could threaten us with a dangerous avian flu strain. We can be thankful that this year’s flu, while surprising in some respects, is nonetheless a garden-variety rather than pandemic strain.

While influenza’s wiles deserve our respect, they are no cause for panic. Even in this challenging year, we can prevent 4 out of 10 cases with vaccination, and effectively treat 95 percent of the rest with medication. Vaccination may reduce flu severity -- even when not preventing flu outright. The flu may have fooled us, but you and your doctor still have means to fight back effectively.