Officials: Flu season could be severe

This year's flu season could be more severe than most, public health officials said Thursday.

That's because the predominant strain of flu circulating the nation, the influenza A H3N2 virus, tends to lead to more hospitalizations and more deaths, said Dr. Tom Frieden, director of the Centers for Disease Control and Prevention. The CDC said that the H3N2 virus was the predominant strain during the 2012-2013, 2007-2008 and 2003-2004 flu seasons, which had the most flu-related deaths in the past decade.

Compounding the problem, officials said, is the fact that a strain of the virus has 'drifted,' meaning it has antigenic or genetic changes. This means the 145 million doses of flu vaccines drug manufacturers have distributed may not be as effective.

'The virus is different enough that the vaccine's protection could be lowered,' Frieden said.

Roughly 90 percent of flu cases have been identified as the H3N2 strain, Frieden said, and half of those cases are the drifted strain.

On Thursday the Iowa Department of Public Health said that while three strains of the flu are circulating in Iowa, the 'drifted' strain has not been confirmed by testing in the state.

The CDC first became aware of the drifted strain in March. However, there was no way to tell how predominant it would become because flu activity was low.

Flu vaccines protect against three or four different flu viruses. A committee of experts pick which viruses to include in the vaccine months in advance so the vaccine can be produced in time for the upcoming flu season, the CDC said.

There is always the possibility that viruses will drift during that time. Frieden said that because it takes about four months to manufacture a new vaccine it's too late in the season to produce a new vaccine to protect against the drifted strain.

Despite the drifted strain, the CDC still recommends flu shots for everyone 6 months of age and older. It is especially important for young children, people 65 and older and pregnant women.

'While the vaccine's ability to protect against drifted H3N2 viruses this season may be reduced, we are still strongly recommending vaccination,' said Dr. Joseph Bresee, chief of the influenza epidemiology and prevention branch at CDC. 'Vaccination has been found to provide some protection against drifted viruses in past seasons. Also, vaccination will offer protection against other flu viruses that may become more common later in the season.'

For those who do get the flu, the CDC said doctors should prescribe patients influenza antiviral drugs within the first 48 hours after symptoms appear. However, this is a practice that isn't always followed.

Frieden said that only one in six people with flu-like symptoms are prescribed antiviral drugs, including Tamiflu (oseltamivir) and Relenza (zanamivir).

'It's not perfect,' Frieden said. 'I wish we had better drugs. I wish we had a better vaccine.'

But early treatment can make a difference, he said.

Influenza activity is low across the United States, but is increasing in parts of the country, the CDC said. So far this year there have been five pediatric deaths across the country.

The CDC said four of those children had the H3N2 virus and three had the drifted variation of the virus.