On July 20, 2003 two neighbors who had both attended the same block party in Lake Worth, Palm Beach County, Florida, reported to the hospital with chills and fever. Soon after, a third individual who had been having chills and fever since July 12, 2003 sought medical attention.    All were diagnosed with Plasmodium vivax, one of 4 species of human malaria. All were treated; all recovered fully.

Over the next month, 4 additional cases were reported by the Palm Beach County Health Department.  An epidemiological field team interviewed all 7 patients, but few common elements connected the cases.

One of the most important questions in understanding malaria is:   Where did the mosquito transmission events occur?  Where were the patients when they were bitten by Anopheles mosquitoes?  If health workers knew the answer to that question, then the mosquitoes could be eliminated and further disease would be stopped.

Two different approaches were followed. First, locate the larval developmental sites. These are usually permanent ponds associated with floating vegetation. This is where the female mosquito lays her eggs. This is the source of the next generation.   If these sites can be located and treated the problem can be eliminated.  The second approach is to find the adults. This is difficult because the adult mosquitoes are mobile and can fly several miles from the ponds where they developed. Finding adult Anopheles mosquitoes is important because it is the adult female that transmits the malaria parasite when she takes blood for the development of her eggs. Male mosquitoes do not feed on blood.

Both larval and adult Anopheles were found, but in low numbers. The search continues. The malaria alert is still in effect in Palm Beach County.