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Not always the flu: Some may have other viruses

An early flu season, complicated by an aggressive strain of a stomach virus, has spread misery across the United States.

Boston’s mayor Thomas Menino declared a public health emergency and hospitals in some cities reported their already stretched emergency rooms were filling up with patients. More than 2,200 people have been hospitalized with the flu since October nationwide, according to the Centers for Disease Control and Prevention, and at least 18 children have died nationwide -- a reminder that flu can be deadly and unpredictable.

Public health officials said while the season is off to an early start, the influenza virus doesn’t so far seem to be doing anything especially unusual. They’ve been urging people since last fall to get vaccinated against the flu and to take precautions, such as frequent handwashing, to avoid infection. 

But this year, in addition to the usual colds, there's also a strain of a virulent stomach bug, called norovirus, making people sick around the world and in the United States. Patients who are sick may have a hard time telling the difference. Norovirus causes flu-like symptoms as well as vomiting and diarrhea. In the past few weeks, 250 people at a Mormon missionary training center in Provo, Utah, became sick with norovirus, the Associated Press reports. In Mill Valley Calif., two died after an outbreak of norovirus at a senior care facility over Christmas sickened 60. 

Data from the Centers for Disease Control and Prevention shows only about a third of all people with flu-like symptoms actually are testing positive for influenza. So two-thirds of the sick people have something else.

Unlike for flu, there's no vaccine for norovirus. There's also no treatment except what health professionals call supportive care – rest, fluids and ibuprofen or acetaminophen for muscle aches. Some patients with influenza can take a pill called Tamiflu. It doesn’t cure the virus but it can cut a few days off the week or so that flu usually makes people ill, if it’s taken within 48 hours of the first symptoms. 

Twenty-nine states and New York City are now reporting high levels of influenza-like-illness and more than nine states are reporting moderate levels of flu-like disease, according to the Centers for Disease Control and Prevention. 

CDC says about 8 out of every 100,000 people are being hospitalized for flu. “This is high for this time of year,” says Dr. Joe Bresee of the Centers for Disease Control and Prevention’s Influenza Division.

In a severe year, as many as 36,000 Americans die from influenza and 200,000 go into the hospital. While most who die are elderly, every year previously healthy children and young adults can also die.

“While we can’t say for certain how severe this season will be, we can say that a lot of people are getting sick with influenza and we are getting reports of severe illness and hospitalizations,” Bresee added. “Anyone who has not already been vaccinated should do so now.”

Vaccine makers have distributed 128 million doses out of about 135 million doses that they plan to make. 

The vaccine protects against three strains of the flu virus, but there’s a fourth strain circulating at low levels that is not affected by the vaccine.

CDC will update its statistics on flu Friday. It said last week that more than five percent of people seeing their doctors complained of flu-like symptoms, which is more than twice as many as this time last year. But last year was an unusually mild flu season.

“While the timing of influenza seasons also is impossible to predict, based on past experience it’s likely that flu activity will continue for some time,” the CDC cautions. Flu season usually lasts at least three months and the United States typically gets hit the worst in January and February.

Influenza-associated pediatric deaths have been reportable to CDC since the 2004-2005 season. To date, CDC has received reports of 18 pediatric deaths this season. More information about reported pediatric deaths is available at the Influenza-Associated Pediatric Mortality web application.

One factor that may indicate increased severity this season is that the predominant circulating type of influenza virus is influenza A (H3N2) viruses, which account for about 76 percent of the viruses reported. Bresee explains “typically ‘H3N2 seasons’ have been more severe, with higher numbers of hospitalizations and deaths, but we will have to see how the season plays out.”

So far this season, more than 90 percent of the influenza viruses that have been analyzed at CDC are like the viruses included in the 2012-2013 influenza vaccine. The match between the vaccine virus and circulating viruses is one factor that impacts how well the vaccine works. But Bresee cautions that other factors are involved.

Related stories:

Bad flu season worsens; Boston declares a state of emergency

Who gave you the flu? New app, docs place blame

How to protect yourself from the flu? Wash your hands