Worst Flu Outbreak in Recent History Strikes United States

A nasty flu strain and the worst whooping cough outbreak in 60 years are making for a rough flu season.

By + More

The worst flu season in recent memory has led Boston to declare a public health emergency and has coincided with outbreaks of other nasty ills across the country.

The Centers for Disease Control and Prevention says that 41 states are experiencing widespread flu activity, and the agency estimates 128 million doses of the flu vaccine have been administered this month, which constitutes 95 percent of the estimated 135 million doses manufacturers planned to make this year.

[PREVIOUSLY: Global Flu Pandemic 'Inevitable,' Expert Warns]

Among the worst hit thus far is the city of Boston, which has had 700 documented cases of the flu already, 10 times as many as the 2011-2012 flu season's 70 documented cases. Already, 18 people have died in Massachusetts from the flu, which has struck four to five weeks earlier than in years past. The outbreak led Mayor Thomas Menino to declare a public health emergency Wednesday morning.

"This is not only a health concern, but also an economic concern for families, and I'm urging residents to get vaccinated if they haven't already," Menino said. "It's the best thing you can do to protect yourself and your family. If you're sick, please stay home from work or school."

CDC data shows this year's flu has struck early and often. Doctor visits for flu-like symptoms are well above the baseline, and if current trends continue, could soon eclipse the previous highs, including the 2009 swine flu pandemic.

[ALSO: MRSA Superbug Found in British Milk]

Google uses search terms related to the flu to predict the virus's spread, in many cases pre-empting the CDC's official reports, which take two weeks to compile. Google's flu trends data for the United States underscore this year's early and severe outbreak.

One reason for the unusually high number of cases could be a proliferation of ills that cause "flu-like symptoms." In addition to a strong seasonal flu virus, this year's ills have included a surging new norovirus—a gastrointestinal bug often called "cruise ship flu"—and the worst outbreak of whooping cough in 60 years, according to the New York Times.

Both CDC's data on flu-like symptoms, defined as a fever of 100°F or greater and cough or sore throat, would therefore include all three illnesses. But the confirmed flu cases are also well above average, according to the agency, indicating a stronger than normal seasonal flu virus. One reason for this could be the particular strain of flu circulating. The CDC estimated 76 percent of the cases reported were a result of the influenza A (H3N2) virus.

[MORE: Flu Season Hits Early and Hard in the Northeast]

"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," Dr. Joe Bresee of the CDC said in a statement, adding that the documented cases were "high for this time of year."

"Reports of influenza-like-illness are nearing what have been peak levels during moderately severe seasons," Bresee said. "Anyone who has not already been vaccinated should do so now."

More News: