Malaria and dengue can be difficult to distinguish. Symptoms are very similar. They typically include a high temperature, or feeling hot or shivery, a headache and feeling or being sick. And both diseases are vector-borne diseases spread by mosquitoes. But the two infections need different treatments. A recent study found dengue was going undiagnosed in children in Kenya. They were being treated with anti-malarial and anti-microbial drugs when, in reality, they didn’t need them. It also raised the question of whether the burden of dengue in Africa is actually far higher than thought.

The study into the high dengue burden and circulation of all dengue serotypes looked at more than 1,000 children. Each had visited an outpatient clinic in western and coastal Kenya with a fever between 2014 and 2017. The study tested blood samples from each of the children and found that 40% of them had evidence of the dengue virus in their bloodstream. Without those tests, it would have been hard to diagnose dengue. After all, their symptoms would have been similar whether they had dengue or not.

High levels of dengue in Kenya

The study noted that “the level of dengue we detected was surprisingly high” and “the number of concomitant (concurrent) serotype infections was also high and unexpected”. Moreover, the children with dengue had all four serotypes among their infections when the researchers hadn’t expected to find DENV-4, which is the dengue serotype least reported in Africa. 

Half of the children with dengue also had malaria. For some, their dengue was causing their fever; for others, it was their malaria. In each case, the other disease remained asymptomatic. 

Prescriptions for anti-malarial and anti-microbial drugs were much higher among children with dengue. This, the study suggests, indicates “severe disease in this group” and supports the idea that dengue was indeed the cause of their fever.

Understanding the distinction is essential, according to the study, because “asymptomatic dengue infections provide a major reservoir for human-to-mosquito dengue transmission”. 

Anti-malarials and anti-microbials overprescribed 

Of the 141 children found to have dengue but not malaria, doctors had prescribed an anti-malarial drug for 29 and an anti-microbial drug for 75 while only 12 didn’t receive either. This finding supports previous research, the study reveals, that shows malaria is over-diagnosed and anti-malarial drugs are over-prescribed. It also indicates that anti-microbial medications are commonly prescribed for fever in developing countries when the exact cause is unknown, which would explain the anti-microbial drugs being over-prescribed. 

Over-prescription of both anti-malarial and anti-microbial drugs can lead to drug resistance developing. Added to that, it can mean doctors need to sometimes treat patients for unwanted side effects. 

The study concludes by suggesting an enormous burden of dengue among children with a fever in Kenya. It finishes by saying “dedicated investments to develop a reliable dengue point-of-care diagnostic is urgently needed” along with “knowledge of the spatial-temporal dynamics of dengue circulation throughout Africa to inform a coordinated public health response in an increasingly interconnected world”.

Is dengue being under- or even over-diagnosed where you live? We’d love to hear your thoughts.