Flu continues to expand its reach in the United States this season with 43 states experiencing either high or widespread flu activity, mostly resulting from circulation of drifted H3N2 viruses, according to the Centers for Disease Control and Prevention (CDC).

generic influenza virion
3D influenza/CDC

Patient visits to doctors for influenza-like-illness (ILI) are now almost even with the peak of 2012-2013 season, the last time H3N2 viruses predominated. Relatively higher flu hospitalization rates seen so far this season are similar to what has been observed during some past H3N2-predominant seasons.

For week 52 of 2014, overall flu-related hospitalizations were 12.6 per 100,000 people, which is comparable to the 13.3 per 100,000 overall hospitalization rate seen during the same week of the 2012-2013 season, but higher than the 8.9 per 100,000 rate observed during week 52 of 2013-2014, which was an H1N1-predominant season.

Additionally, another 6 flu-associated pediatric deaths are being reported this week, bringing the total number of flu pediatric deaths that have been reported this season to 21. 11 states have reported pediatric flu deaths so far in the 2014-2015 season: Arizona [1], Colorado [1], Florida [2], Kansas [1], Minnesota [3], North Carolina [2], Nevada [1], Ohio [2], Tennessee [3], Texas [3], and Virginia [2].

H3N2 viruses continue to predominate in the United States this season, accounting for more than 95 percent of all influenza reported to CDC from U.S. WHO and NREVSS collaborating laboratories. In the past, H3N2-predominant seasons have been associated with more severe illness and higher mortality, especially in older people and young children, relative to H1N1- or B-predominant seasons.

Most of the H3N2 viruses circulating are “drifted” or different from the H3N2 vaccine virus; suggesting that the vaccine’s ability to protect against those viruses may be reduced.

CDC continues to recommend flu vaccination even when there are drifted viruses circulating because the vaccine can still prevent infection and also prevent serious flu-related complications in many people.

CDC also recommends flu antiviral drugs for treatment of influenza illness in people who are very sick with flu or people with the flu who are at high risk of serious flu complications. Influenza antiviral drugs are a second line of defense against the flu to treat flu illness. These prescription drugs work best when started soon after influenza symptoms begin (within 2 days), but persons with high-risk conditions can benefit even when antiviral treatment is started after the first two days of illness.

The CDC also suggests:

  • Try to avoid close contact with sick people.
  • If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.)
  • While sick, limit contact with others as much as possible to keep from infecting them.
  • Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
  • Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
  • Avoid touching your eyes, nose and mouth. Germs spread this way.
  • Clean and disinfect surfaces and objects that may be contaminated with germs like the flu.