Mosquitos are more dangerous than rattlesnakes. A dozen African diseases have evolved transmission tricks using mosquitos. Sucking blood from a diseased person infects a mosquito. The germs multiply inside her body and migrate to her saliva glands. They are injected with her saliva at her next blood meal. A new victim is infected. Mosquito-borne diseases have spread throughout the world, killing countless millions over the course of human history.
The earliest and most successful public health programs have attacked the mosquito. Yellow fever had been the scourge of military campaigns throughout history. It looked like the Spanish-American War would be no different. US forces in Cuba were taking heavy loses to the disease. Carlos Finlay had proposed that mosquitos might be the cause of the disease. Others had blamed everything from human contact to the alignment of the stars. Walter Reed led a team of US Army doctors who confirmed Finlay's hypothesis. The Army cleaned up Havana—eliminating places for mosquitos to breed. The yellow fever epidemic faded away. The US Army did the same thing in Panama. Controlling mosquitos there allowed the US to build the Panama Canal where yellow fever and malaria had ended an earlier French attempt.
The battle against the mosquito is far from over. Mosquito-borne diseases still sicken almost a billion people every year. They kill millions to this day. Despite an effective vaccine and efforts to control its Aedes mosquito carrier, yellow fever kills one human every fifteen minutes. Malaria had nearly been eliminated by the campaign against its Anopheles mosquito carrier. Malaria has rebounded since the banning of DDT. It is once again the world’s leading killer of pregnant women and young children. Malaria kills one every thirty seconds. Modern transportation is spreading mosquitos and their diseases to new areas with vulnerable populations. West Nile virus, eastern equine encephalitis, and tularemia have all reached the US mainland.
A new virus threat has broken out of the African jungle and erupted in Brazil. Zika fever is a mild infection in most adults. Occasional serious side effects include Guillain-Barré syndrome. That's an autoimmune disease where the body's immune system attacks the peripheral nervous system. Critical bodily functions are interrupted and medical intervention is required. The virus's ability to cross the placenta and infect a fetus is a special problem. The child's nervous system development may be stunted. Underdeveloped brains and undersize heads may result. Could that be just another manifestation of its rare Guillain-Barre effect? This birth defect is receiving worldwide attention. Women of childbearing age are encouraged to avoid travel to zika areas, or to delay pregnancy.