Outbreaks of influenza are getting an early start this year in part because of cold weather gripping much of the USA and low efficacy associated with this year's flu vaccine.
It's still too early to say whether this winter will be a bad season for the flu, but epidemiologists in 36 states already have reported widespread influenza activity to the federal Centers for Disease Control and Prevention in data released Friday. Twenty-one of those states show a high number of cases.
"It's just one of those years where the CDC is seeing that this strain of flu is only somewhat covered by the vaccine that was given this year," said Jennifer Radtke, manager for infection prevention at the University of Tennessee Medical Center in Knoxville. "They're seeing that it's anywhere from 10% to 33% effective, so any time there’s a mismatch between the vaccine and the circulating strain of the flu, you’re going to see more cases."
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Peak flu activity in the U.S. usually occurs around February.
Vaccine effectiveness varies from year to year though recent studies show that a flu shot typically reduces the risk of illness by 40% to 60% among the overall population when the circulating virus is matched closely to the vaccine virus, according to the CDC.
Because only a certain percentage of people with flu symptoms go to hospitals and get tested, it can be challenging to track the actual number of people affected, Radtke said. False negative results for flu tests are also common, so it’s likely the number of people with the flu is much higher.
From the start of the flu season, which begins in October and lasts until May, Arizona has reported a nearly ninefold increase in the number of cases compared with the same period last year, according to the state Department of Health Services.
"It's not uncommon to see (flu) this time of year," said Radtke in Knoxville. "But we've had cold Decembers before and not had flu."
Flu symptoms include fever, body aches, chills, fatigue, cough and a sore throat. The illness typically passes within a few days but can be especially dangerous to the very young, the very old, pregnant women and those with respiratory problems.
Influenza can develop into pneumonia, an infection that causes the lungs' air sacs to become inflamed and fill with fluid.
Deaths already have occurred in some states this flu season. Among them:
• In Arizona, the state is reporting one death of a child in its latest tally; however, an otherwise healthy 20-year-old mother of two in Phoenix died Nov. 28, one day after being diagnosed, CBS News reported.
• In California, at least 10 people younger than 65 have died, according to the San Francisco Chronicle. An 11th death occurred Thursday. The state does not track flu-related deaths among those 65 and older.
• In Delaware, a 47-year-old man with underlying health problems and an 83-year-old woman have died, state health officials said.
• In North Carolina, 12 people, including a child, have died.
• In South Carolina, seven have died. All were age 65 or older.
Getting a flu shot now is still one way to combat the virus even though it can't promise total immunity, health officials say.
More insurers fully cover the cost, and pharmacists in all states now can administer the vaccinations, according to the American Pharmacists Association trade group.
"People are able to come in to the pharmacy — especially a 24-hour pharmacy like this one where you can come in at literally any time — and be in and out usually within 15 minutes," said Jason Lind, a Walgreens pharmacist in St. Cloud, Minn.
Also to keep the germs at bay, wash or sanitize your hands frequently, especially if you're touching shared surfaces such as shopping carts in public places; clean faucet and toilet handles frequently at home to reduce transmission of the virus within your family; cover your mouth when coughing; stay home when you're sick; stay away from sick people; and avoid touching your face.
It also pays to stay well rested and hydrated so if you do come in contact with a flu virus, your body is prepared to fight it off.
If you're already feeling ill, get to a doctor as quickly as possible.
Antiviral prescription drugs such as Tamiflu can lessen the severity of influenza for people who have had flu symptoms for two days or fewer and prevent complications such as pneumonia. But they also can have side effects, so a flu shot while you're well should be your first choice.
“It can take up to two weeks to build full immunity to the flu after you are vaccinated," said Dr. Cara Christ, director of the Arizona Department of Health Services. "So I encourage everyone who has not yet had a flu shot to get one today before the holidays.”
Contributing: Megan Janetsky, The Arizona Republic; Joe Szydlowski, The Salinas Californian; Maddy Lauria, The (Wilmington, Del.) News Journal; Liv Osby, The Greenville (S.C.) News; Andrew Fraser, St. Cloud (Minn.) Times; The Associated Press. Follow Rachel Ohm on Twitter: @rachel_ohm