Rainfall, Temperature and Dengue Risk: New Insights from Rio

Aedes aegypti mosquito (cdc.gov)

Here is a study by researchers from Brazil that looked at the relationship between dengue activity and climate in Rio de Janeiro from 2001 to 2009. Using statistical modeling, they found that a 10-millimeter rise in rainfall led to a 6% increase in dengue cases in the subsequent month, and a 1 degree celsius rise in temperature led to a 45% increase.

Dengue is a viral infection transmitted by Aedes aegypti (and Aedes albopictus) mosquitoes; it is the most common mosquito-borne viral infection. It causes an acute febrile illness characterized by severe pain (giving it its colloquial name: "breakbone" fever). The disease is associated with significant morbidity.

The findings in the above study are not surprising: increased temperature allows the mosquitoes that carry dengue to breed and feed more efficiently. Increased rainfall can increase potential breeding sites for these mosquitoes (which breed in freestanding water). This study adds to the growing body of literature linking climate and infectious disease activity.

A warmer world is one in which the various vectors for tropical infections (especially mosquitoes) will enjoy a broader environment in which to breed and feed. More research into the relationship between climate change and emerging infectious diseases is warranted.