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The Clinical Quandaries of Counting Dengue Cases

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The Clinical Quandaries of Counting Dengue Cases

Though the dengue virus confounds public health officials in so many ways—from having four distinct serotypes to its uncooperative nature regarding vaccine philosophy—one might think that at least disease control experts would have an easy task in counting who has it, who had it and who didn’t.

Yet the collecting of accurate data about dengue fever is just as complicated as anything else involved with this old and stubborn disease. For instance, some countries where it thrives report only the serious cases of dengue—the deadly hemorrhagic variety that can kill. Others count every single dengue case based on a clinical diagnosis, and some just report those cases that have been confirmed in a laboratory.

“One of the clinical quandaries with dengue,” says Anna Durbin, MD, an associate professor in International Health, “is that a child can come in with a fever and you don’t know if it will progress to severe dengue or not.”

First infections of dengue are often mild, masking the true nature of the illness. Three out of five cases of dengue infection are asymptomatic or mildly symptomatic of dengue cases, says Durbin. Because there is no cure, for a victim—usually a child in most endemic countries—the only remedy is the same as for most fevers: rest, drink fluids and weather the storm.

The WHO says that in some countries during the peak of dengue season, so many children complain of dengue-like fevers that the clinical and lab capacity of hospitals is overwhelmed.

“Not every suspected case of dengue is serologically or biologically confirmed,” says Durbin. “It’s so labor intensive and expensive. Most of the reporting based on clinical case criteria is suspect. Some children will get better. Others will crash. It’s difficult to know which is which.”

In Africa, says Durbin, where the virus originated more than 2,000 years ago, cases of dengue are often misdiagnosed as malaria. Doctors will do a blood smear and find evidence of the parasite that causes malaria, she says, and then quickly diagnose malaria. “Even though people there are chronically infected with malaria and may be asymptomatic with it,” says Durbin, “they still have a parasite burden in their blood. But if the doctor sees that parasite you’ll be treated as malaria.”

It’s rare for a person who has never had dengue to contract the most severe form—hemorrhagic fever. But those who have been infected in prior years are very likely to develop the severest form. Thus, someone who had an asymptomatic case of dengue and didn’t know it might not appreciate the risks of a second infection.

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  • Ifelayo

    Hyattsville, MD 07/09/2010 08:51:20 AM

    I like this display of a combination of efforts to fight an old scourge! With patient persistence following these tracks, we should overcome Dengue and hopefully Malaria too...

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