Last month the Centers for Disease Control and Prevention (CDC) warned that the current 2014-2015 flu season could be severe based on early data. Now the CDC has announced that statistics released this week indicate that the influenza outbreak in the United States reached the epidemic threshold during the week ending on December 20. The number of states reporting a “high” level of influenza activity jumped from 13 to 22 in one week.
Influenza, or the flu, is a contagious respiratory illness caused by various flu viruses. Symptoms of the flu include fever, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue. Complications of the flu include pneumonia, bronchitis, sinus and ear infections, and death. Influenza is not the same as the stomach flu, which is characterized by nausea, vomiting, and diarrhea.
Commented Erin Burns, a health communications specialist with the Influenza Division at the CDC, to USA TODAY, “At this time, all of CDC’s influenza surveillance systems are showing elevated flu activity, indicating that we are in the midst of this season’s flu epidemic.”
Fifteen children have already died as a result of the flu. Pediatric influenza deaths were reported in nine different states: Arizona (1), Colorado (1), Florida (2), Minnesota (2), North Carolina (2), Nevada (1), Ohio (2), Texas (3), and Virginia (1).
“It is a bit early to make any kind of characterization about pediatric deaths this season, but from looking at the curve going back to 2011-2012, it doesn’t seem like anything unusual is happening.”
The CDC cautions that pediatric death data “typically lag behind” other measures for the severity of a flu season. Pediatric deaths generally range between 35 to 171 cases in a typical flu year. During the 2009 influenza pandemic, 348 children died of influenza-related causes. However, the recent increases in flu activity including influenza-related hospitalizations and deaths are so far a “typical pattern for the flu season.”
The most common flu viruses in the United States this year have been seasonal influenza A H3N2 viruses, which typically cause more severe flu illnesses, hospitalizations, and deaths. The CDC also reports that the most common strains of circulating flu viruses are so-called “drift variants” of the H3N2 viruses used in the current formulation of the influenza vaccine. Drift variants are viruses with antigenic or genetic changes from the strains in the vaccine, meaning that the vaccine strains are not a perfect match for all circulating viruses.
“Traditional flu vaccines (called trivalent vaccines) are made to protect against three flu viruses; an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. In addition, there are flu vaccines made to protect against four flu viruses (called ‘quadrivalent’ vaccines). These vaccines protect against the same viruses as the trivalent vaccine and an additional B virus.”
However, despite an increase in drift variants, the influenza vaccine can still provide partial protect against influenza infection and may also reduce the severity of symptoms in individuals who contact the flu. The CDC thus continues to recommend vaccination with the seasonal flu vaccine.
The CDC recommends vaccination against the flu to almost all individuals over the age of 6 months, especially individuals at high risk from flu-related complications including children under the age of 5; adults 65 and older; pregnant women; and individuals with chronic health conditions such as asthma, diabetes, heart or lung disease, and kidney disease. Pregnant women can receive the flu shot, and vaccination during pregnancy can provide some protection to babies under the age of 6 months.
The CDC will continue to monitor flu activity in the country.
CDC: Flu has reached epidemic level, 15 child deaths in U.S.: http://mashable.com/2015/01/01/flu-levels-us/
This season’s flu activity has reached the epidemic threshold, the CDC says: http://www.washingtonpost.com/news/to-your-health/wp/2014/12/30/this-seasons-flu-activity-has-reached-the-epidemic-threshold-the-cdc-says/
Weekly U.S. influenza surveillance report: http://www.cdc.gov/flu/weekly/
ILINet State Activity Indicator Map: http://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/images/ILIIntensity51_small.gif