The number of flu cases in Pennsylvania this season has potentially peaked at the highest levels since 2009, and at a little less than double the numbers of previous years, according to data from the state Department of Health.
Two weeks ago, there were 13,000 flu cases reported, which health officials hope is the peak of the flu season this year. The number of flu cases fell last week to a little above 10,000, which is still higher than where other flu seasons have peaked.
According to the Department of Health, other flu seasons in the last eight years have peaked at around 8,000 cases, including 2009 when the country dealt with the swine flu. Half of those seasons since 2009-10 only reached 4,000 cases or fewer.
This season, the number of reported flu cases has stayed above 4,000 since the first week of January.
Dr. John Goldman, infectious disease specialist of UPMC Pinnacle, said this flu season has been worse and lasted longer because of the type of strain that is the most prevalent in this year’s cases: H3N2.
“Anytime we have that strain, we see more deaths,” he said. “It’s a strain that normally creates more severe symptoms, more hospitalizations and more deaths. Simply, we’re seeing more severe (cases), and this has lasted longer than the typical flu season.”
According to the Department of Health, 64.37 percent of the cases this season up to Feb. 17 in the state were due to the H3N2 virus.
H3N2 was also blamed for the increase in hospitalizations and deaths in the 2014-15 flu season, in which its vaccine was only 19 percent effective, according to the CDC and Associated Press.
Part of the reason that number is high is because vaccines typically aren’t very effective against that strain, Goldman said.
The Associated Press reported that this season’s flu vaccine is 36 percent effective overall. The reason the number is low is because of its effective rate on the one strain.
The vaccine was determined to be only 25 percent effective against H3N2, but it was deemed 67 percent effective against H1N1 (swine flu) and 42 percent effective against Type B influenza.
Goldman said that one reason a vaccine for H3N2 is often ineffective is because vaccines are created with an antigenic drift. The vaccine deals with variations of flu strains to cover the following flu season, and H3N2 is harder to predict, along with technical issues with growing the virus, he said.
Though the vaccine is less effective against one strain, Goldman said it’s still important to get a flu shot. Even though the vaccine may not 100 percent prevent someone from getting the flu, he said it will reduce the severity of symptoms.
“If you get a flu shot, the risk of death goes down 50 percent,” he said.
He said those who have not yet received a flu shot can still get one. The Department of Health this week stopped short of claiming that the flu season had peaked, but the number of cases could remain high even as the total falls.
Flu seasons usually start in October and surveillance of cases ends in May, but where each season peaks varies. Some have peaked before January, and others peak in January and February. The 2015-16 season peaked in March, according to the Department of Health. State data shows that flu cases can linger through April.