3. Middle East respiratory syndrome (MERS)
As if bat-borne diseases like Ebola and Marburg weren’t enough, it turns out the flying mammals are also host to another deadly disease: Middle East respiratory syndrome, or MERS, a viral respiratory disease that was first identified in 2012 in Saudi Arabia. However, though MERs originated in bats, its major reservoir in the Middle East is likely dromedary camels, according to the WHO.
The MERS coronavirus (MERS-CoV) is closely related to SARS and the 2019-ncOv coronavirus currently spreading in China. People who contract MERS develop severe respiratory illness, including fever, cough and shortness of breath. As of 2020, 2,494 cases of the illness had been reported, mostly in Saudi Arabia. About 34% of those who contracted the illness died, according to the WHO.
4. Dengue
Mosquito-borne viruses — of which dengue is one of many — kill an estimated 50,000 people worldwide every year, according to the WHO and the CDC. (Malaria isn’t included in that estimate because it’s caused by a parasite, not a virus.)
Dengue (pronounced den’ gee) is a disease that can be caused by one of four related viruses: DENV 1, DENV 2, DENV 3 and DENV 4. Mosquitos — usually the species Aedes aegypti (shown here), but sometimes A. albopictus — spread the disease from one person to the next. It’s not possible for people to catch dengue from one another. People with the disease typically experience flu-like symptoms. Sometimes the virus leads to a potentially lethal complication known as “severe dengue” or dengue hemorrhagic fever, with symptoms that include fever, abdominal pain, vomiting, bleeding and trouble breathing, according to the WHO.