(CNN) -- California is being hit hard with a whooping cough epidemic, according to the state's public health department, with 800 cases reported in the past two weeks alone.
The agency says that there were 3,458 whooping cough cases reported between January 1 and June 10, well ahead of the number of cases reported for all of 2013.
This is a problem of "epidemic proportions," the department said. And the number of actual cases may be even higher, because past studies have shown that for every case of whooping cough that is reported, there are 10 more that are not officially counted.
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