- Jonathan Patz / Marjorie Share
EcoHealth101 – www.ecohealth101.org
Vectors are critters that transport bacteria, viruses, and parasites. Case studies may offer clues to how global warming will affect vectors – and the deadly illnesses they spread.
Think of vectors as the taxis of the disease world. Bacteria, viruses, and parasites ride from one person (or animal) to another. As the vector goes about its life, the disease spreads. Vector-borne diseases are some of the most deadly and unpredictable medical problems that humans face.
Most vectors are bloodsucking arthropods – animals with external skeletons, segmented bodies, and jointed limbs. "Superstar" vectors include fleas, mites, ticks, and (of course) mosquitoes. Lapping blood from animals or humans, these creatures also pick up disease-causing microbes or germs. The vector doesn’t get sick. But it does transfer the microbes to the next person it bites. The microbes then infect that person.
One of the most vicious vector-borne diseases of all time is the plague, more colorfully known as the Black Death. In just six years (1347-52), bacteria killed a quarter of Europe’s population. Fleas carried the plague from rats to humans.
How will global warming affect vector-borne diseases? Scientists say it’s difficult to know for sure. One big concern is that rising temperatures could affect rainfall patterns. Some places may grow warmer and wetter – and perhaps more prone to disease
In the U.S., for instance, encephalitis (brain swelling caused by a mosquito-borne virus) thrives when wet, warm winters give way to hot, dry summers. In the tropics, malaria epidemics often follow the rainy season. More rain could mean more malaria.
Then again, high temperatures could kill off tick or mosquito vectors in some places.
We just don’t know.
There’s a way to find clues, however. That’s by looking carefully at disease case studies, such as malaria. Seeing how climate affects each disease can help scientists hypothesize about how other diseases may respond to mate changes.
The links below take you to three case studies: