Malaria and yellow fever have not been completely eradicated in the U.S. as health concerns, but are not the threat they once posed to American health. We are fortunately distanced from their historically geographical concentrations, although malaria was not uncommon in the American South until the government’s eradication campaign from 1947-1953. And there have been sporadic outbreaks of yellow fever in the U.S., the last being in New Orleans in 1905.
In the early 1900’s, it was noted that the mosquitoes carrying these parasitic (malarial) and viral (Yellow Fever) infections deposit their larvae in clean water, and from that time onward people were educated to keep ponds near homes and indoor vessels of water covered, especially during warm months, knocking down the mosquito population by preventing reproduction.
The Anopheles mosquito, the greatest vector for transmitting malaria with its bite, does not thrive over 68°; its reproductive cycle is interrupted and it is unable to spread the most severe of the four types of malaria. Its malaria-infected population sticks largely to the warm, tropical climates of Africa (south of the Sahara Desert), Central America, southeast Asia, and India.
In the 1940’s, malaria reached epidemic proportions among Americans working on the Panama Canal (at one point, 21,000 of 26,000 workers had been treated for the disease). The U.S. Army Medical Corps undertook an aggressive campaign to eradicate the mosquitoes that were the vectors for this parasitic disease. Affected people were treated with quinine or chloroquine, anti-malarial agents (see also SamMontana’s Factoid on Artemisinin), and educated to wear long-sleeved clothing and use mosquito netting around their beds and on outbuildings such as porches, patios and gazebos. Swamplands were drained, and mosquito larvae on clear, standing water were sought out and killed. The regimen was effective, and was also applied to 13 states in the American South. In 1943, the addition of DDT, specifically deadly to mosquitoes, made eradication efforts even more successful, and by 1952, malaria was all but eradicated in the U.S., reaching a status of near world eradication by 1963. However, by this time, DDT-resistant strains of mosquitoes were beginning to appear, and by the 1970’s the U.S. populace began to protest about the possible adverse effects of being sprayed with DDT.
A vaccination was developed for Yellow Fever in 1927, and has been refined since that time. It is said to be close to 100% effective in preventing both types of the disease, which has an urban strain and a forest (sylvan) strain related to mosquitoes feeding on infected monkeys, then spreading to humans, which is not a frequent occurrence, reserved mostly for Rain Forest population where humans dwell in proximity to these monkeys. The most common outbreaks of Yellow Fever in humans are of the urban variety. Yellow Fever is best prevented by vaccination.
With awareness in the 1990’s of global warming and its effects in climate change and wind patterns, the medical community is increasingly seeing new areas where the infecting mosquitoes can thrive and become a menace. Similarly, wars and their resultant mobilization of populations, can interrupt efforts to keep mosquito populations down, treat malaria victims and vaccinate populations unprotected against Yellow Fever.
So while it can’t be said that the diseases are eradicated, the solutions are known, effective, and available; malaria and Yellow Fever continue to be monitored closely by the CDC and are not considered a large threat within the U.S. at this time.
01.14.09
