As tropical diseases spread under the influence of climate change and increased global movement, the residents of one vulnerable city have found unusual protectors in the form of northern cardinals (Cardinalis cardinalis).
West Nile Virus (WNV) is a mosquito-borne disease that has infected an estimated 780,000 North Americans since 1999. In severe cases, consequences include brain infections that have taken 1,700 lives in the United States alone.
With 3.3 infections per 100,000 people, Georgia has proven surprisingly immune compared to other US cities, considering that one-third of Atlanta-area birds tested for the virus have been infected.
Emory University’s Dr Rebecca Levine was struck by the fact that Chicago has five times as many human WNV infections per capita as Atlanta, even though birds in the area are less likely to be infected than those around Atlanta.
In the American Journal of Tropical Medicine and Hygiene, Levine attributes the difference to the type of birds in the area, and particularly the way that cardinals form a protective shield for Atlantans. The entire US southeast appears to be benefiting to some degree.
WNV is called a “spillover” disease because the virus circulates largely among animals, sometimes spilling into nearby human populations. American robins are particularly active facilitators of the disease, earning the tag “superspreaders”. They harbor the virus at high levels in their blood, giving it back to Culex mosquitoes that bite them, which then carry it on to humans.