INDIANAPOLIS — The seasonal flu outbreak that has killed 40 people so far in Indiana is the state's deadliest in half a decade, records show.
Past years have been tamer, with only three people dying of flu last season. The last such severe flu outbreak occurred during the 2007-2008 season, when 73 people died. Twenty-five people died during the 2010-2011 season, and 18 died of seasonal flu during the 2009-2010 season.
It's too soon to tell whether the spread of flu has peaked yet this season, state health officials said Friday. Flu season typically runs from October to May.
The deadliest flu season since 2000 was the 2003-2004 outbreak, when 91 people died in Indiana.
Flu virus strains change every year, so it can be very difficult to predict the severity of each season, said Pam Pontones, an epidemiologist for the state health department. Death rates from year to year vary widely.
"What we really have to do is work very diligently to conduct surveillance ... to monitor influenza activity and look for signs that the virus may be changing or if there is a particular virus that appears to dominate," she said.
This year, the H3N2 strain appears to be the most prevalent. The flu vaccine does protect against that strain.
People over the age of 65 are typically more vulnerable to the flu, especially those living in long-term care facilities. Of those who have died so far in Indiana this season, 33 were people over age 65 and 38 had underlying medical conditions such as heart disease, diabetes, asthma and renal disease.
"As age goes up, immunity drops," said Arif Nazir, a geriatrician at the Indiana University School of Medicine. "As we age, we sometimes have diseases that lead to decreased ability to fight against infections. ... Our immunity is weaker."
Symptoms of the flu can include fever, cough, runny nose, head and body aches and fatigue. Some people also have vomiting and diarrhea, and some develop pneumonia or other severe complications.