July 29, 2010 -- The H1N1 flu strain that sparked the first influenza pandemic in four decades has caused the majority of flu cases so far in the 2009-2010 season, the CDC says.
CDC spokesman Tom Skinner tells WebMD that the so-called swine flu bug has affected the very young more than elderly people in the current influenza season, which “is not normally the case.”
“We have had a lot more young people get this flu and die than in a normal flu season,” Skinner says.
The CDC’s Morbidity and Mortality Weekly Report for July 30, 2010, says the H1N1 strain has shown “unusual patterns of disease, disproportionately affecting children and young adults and relatively sparing the elderly.”
The MMWR says the proportion of visits to health care providers for flu-like illnesses has been among the highest this season since surveillance began in 1997.
Between April 2009 and June 12, 2010, about 740,000 flu specimens were tested, and the number of laboratory-confirmed cases was about four times the average of the previous four seasons.
Of 91,152 confirmed flu cases in that period, 99.8%, or 66,916, were caused by the 2009 H1N1 pandemic strain, the MMWR says.
Between Aug. 30, 2009, through June 12, 2010, the CDC report says the peak proportion of outpatient visits to doctors for flu-like illness was among the highest seen since current record keeping.
From Sept. 1, 2009, through May 1, 2010, flu-associated hospitalizations for children up to age 4 was 6.7 per 10,000 and youths 5-17, 2.5 per 10,000.
Rates for adults were 2.5 per 10,000 for people 18-49, 3.2 for those 50-64, and 2.8 for those 65 and older.
During the entire H1N1 pandemic season through May 1, 2010, cumulative rates of hospitalization were 8.3 per 10,000 for children up to 4, 3.4 for ages 5-17, 3.0 for people 18-49, and 3.8 for those 50-64. The rate was 3.2 for people 65 and older.