The Centers for Disease Control (CDC) has blamed the H3N2 strain of the influenza virus for the spread of the disease to 43 states, as the flu season gets underway in the US
According to the CDC's latest flu report, the spread is not an epidemic, but the number of cases so far has matched the number of cases at the peak of the flu season last year.
The H3N2 strain is believed to be a mutated version, leaving many people who already received flu shots vulnerable. In addition, H3N2 accounts "for more than 95 percent of all influenza reported to CDC" this season, the statement said.
"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," the CDC affirmed.
"Two factors play an important role in determining the likelihood that flu vaccines will protect a person from flu illness: 1) characteristics of the person being vaccinated (such as their age and health), and 2) the similarity or 'match' between the flu viruses in the vaccine and those spreading in the community," it said.
The CDC, however, continued to stress the importance of the flu shot, particularly for those 65 years of age and older, children under five years of age, pregnant women, and people battling other conditions that can compromise their immunity.
"Overall flu-related hospitalizations were 12.6 per 100,000 people" last week, the CDC reported. But "hospitalization rates are cumulative, so this season's rates will likely continue to rise."
Currently, only pediatric deaths from the flu are reported nationally. Since the start of the flu season - typically sometime in October - 21 children have died as a result of flu-related complications.