CHICAGO (CBS) — The pace of West Nile virus is picking up dramatically in Illinois.

Last week, the state public health department reported 28 Illinoisans had contracted the infection, WBBM Newsradio’s Regine Schlesinger reports.

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Now, that number is up to 48.

LISTEN: WBBM Newsradio’s Regine Schlesinger Reports

Two of the patients have died, including the Lombard village president Bill Mueller.

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The health department reports almost all the Illinois cases have turned up in Cook, Dupage, Lake, Kane and Kankakee counties.

The numbers so far this year are still well below the peak 10 years ago when Illinois had counted 884 human cases and 67 deaths, more than any other state in the country.

The symptoms of West Nile virus are similar to the flu and the best way to prevent the illness is to try to reduce your exposure to mosquitoes which transmit the virus.

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Those most vulnerable to serious cases are the elderly and those with underlying health conditions.