The Centers for Disease Control and Prevention officially declared today that the flu virus has become an epidemic in the United States following the deaths of 15 children so far this season. The agency has reported severe outbreaks in every region of the country. Since last week, the number of states reporting high levels of “influenza-like” illness has increased from 13 to 22. The states with the most severely affected populations are in the south, Midwest and western parts of the country, though researchers are not certain why that is the case. Tennessee has been one of the hardest hit states with six children dying from the flu and 442 children hospitalized at the East Tennessee Children’s Hospital.

According to the CDC, roughly 90 percent of this year’s flu cases have been the H3N2 subtype. There are 17 different types of H particles, or hemagglutinin, which bind the virus to the cells, and nine different types of N particles, or neuraminidase, which are responsible for the spread of the virus throughout the body. Of the various subtypes, the H3 variety, which comprise most of this year’s cases, typically leads to the highest numbers of hospitalizations and deaths.

Compounding the severity of the strain itself is the concerning trend that the flu season has been breaking out earlier and earlier over the last four years. While in prior years the flu season did not peak until February or March, health officials are now seeing it peak at the end of December. Furthermore, this season’s flu vaccine – which health agency officials advise is your best defense against contracting the flu – is now believed to be a poor match for the predominant strain affecting the majority of the population. Many health officials believe that the H3N2 strain mutated, thereby comprising the effectiveness of the vaccine that had been prepared for this season.

The flu is always especially deadly in children, the elderly and individuals with compromised immune systems. While this season appears to be more severe than others, health officials advise that you can reduce your risk of becoming infected with the flu by practicing hand hygiene, coughing and sneezing into your elbow and getting a flu shot, which still will provide some level of protection especially for the most vulnerable categories of the population.