In contrast with some common perceptions regarding 2009 influenza A(H1N1) infections, an examination of cases in California indicates that hospitalization and death can occur at all ages. About 30 percent of hospitalized cases have been severe enough to require treatment in an intensive care unit.
The study is published in the November 4 issue of JAMA.
“Since April 17, 2009, when the first 2 cases of pandemic influenza A(H1N1) virus infection were reported in California, the virus has rapidly spread throughout the world,” the authors write. They add that preliminary comparisons with seasonal influenza suggest that this influenza infection disproportionately affects younger ages and causes generally mild disease.
Janice K. Louie, M.D., M.P.H., of the California Department of Public Health, Richmond, Calif., and colleagues examined the clinical and epidemiologic features of the first 1,088 hospitalized and fatal cases due to pandemic 2009 influenza A(H1N1) infection reported in California, between April 23 and August 11, 2009. On April 20 of this year the California Department of Public Health and 61 local health departments initiated enhanced surveillance for hospitalized and fat…