U.S. officials say this season's flu outbreak worsened last week and it is not clear when the epidemic will peak.
In its weekly report Friday, the Centers for Disease Control and Prevention (CDC) said the number of people hospitalized this season for flu-like illnesses is the highest it has seen since starting its current tracking system in 2010.
It said one out of every 13 visits to the doctor last week was for flu symptoms. Flu remained widespread in every state except Hawaii and Oregon, according to the report.
Anne Schuchat, the CDC's acting director, told reporters 10 children were reported to have died in the week ending Feb. 3, bringing the total number of child deaths from the flu this season to 63. The CDC does not track adult deaths from the flu.
"I wish there were better news this week, but almost everything we're looking at is bad news," Schuchat said.
Flu season usually begins in earnest in late December and peaks around February. This season, the flu was widespread in many states by early December.
Schuchat said it was not clear whether the outbreak had peaked or whether it would still get worse. She also said it was not clear why the flu has been so severe this year.
"So, exactly why we're having such a severe year is difficult to say. It may be a combination of factors: the virus, the weather, it may be the early season that we saw. [The] disease started to increase earlier this past fall and so we may have a longer season by the year's end," she said.
This year's strain
The dominant flu strain this season, influenza A (H3N2), is especially strong and tends to lead to more hospitalizations and deaths than other more common flu bugs.
This year's strain, however, is the same main bug from last winter, which did not have as severe an outbreak. Experts say that they are not sure why the pandemic is so bad this year and that flu seasons are notoriously hard to predict.
Schuchat urged sick people to stay home and said there is still time to get the flu vaccine, which offers some protection. The U.S. will release data next week on the effectiveness of this season's flu vaccine, with some scientists speculating that this season's intense flu virus could be, in part, related to a poorly effective vaccine.
The flu typically affects children and the elderly the most. However, hospitalization rates for people 50 to 64 years old — those who mostly fall under the baby boomer demographic — has been unusually high this season. Officials say the rate of hospitalization for baby boomers is 44.2 per 100,000 people, which is nearly triple what it was last season.
Flu is a contagious respiratory illness that causes such symptoms as fever, cough, muscle aches, headaches and fatigue. Most people who get the flu get better within a week or two. However, some people develop serious complications caused by viral infection of the nasal passages and throat and lungs.