Anopheles quadrimaculatus range in the U.S.

Malaria is one of the last, great killer illnesses on the planet. One by one, illnesses such as polio have been nearly eliminated by vaccines and improved treatments. Malaria has not, and is threatening to reappear in regions that have not seen infections in fifty years. 

Malaria is an illness spread from human to human by the bite of the female Anopheles mosquito. According to the Centers for Disease Control (CDC), of the approximately 430 species of Anopheles, only 30-40 transmit malaria. The United States has had outbreaks of malaria in the last half century, but they all originated with patients who became infected abroad. The CDC points out that:

Of the species of Anopheles mosquitoes found in the United States, the three species that were responsible for malaria transmission prior to elimination (Anopheles quadrimaculatus in the east, An. freeborni in the west, and An. albimanus in the Caribbean) are still widely prevalent; thus there is a constant risk that malaria could be reintroduced in the United States.

The World Health Organization (WHO) estimates that half of the world's population live in areas where they are at risk for a malarial infection. They believe that there were about 243 million cases of malaria in 2008 and 863,000 related deaths.

There are four varieties of malaria parasites that can sicken people: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. Each has a different incubation period and slightly differing symptoms. Each responds to a different drug treatment regimen. The incubation period can be as short as seven days or as long as a year, depending on the variety of parasite. It is very important to identify which malarial parasite is infecting a patient to ensure proper treatment. 

The symptoms of malaria, as the CDC site states, are:

The classical (but rarely observed) malaria attack lasts 6-10 hours. It consists of

• a cold stage (sensation of cold, shivering)
• a hot stage (fever, headaches, vomiting; seizures in young children)
• and finally a sweating stage (sweats, return to normal temperature, tiredness).

Classically (but infrequently observed) the attacks occur every second day with the "tertian" parasites (P. falciparum, P. vivax, and P. ovale) and every third day with the "quartan" parasite (P. malariae). 

More commonly, the patient presents with a combination of the following symptoms:

• Fever
• Chills
• Sweats
• Headaches
• Nausea and vomiting
• Body aches
• General malaise

In countries where cases of malaria are infrequent, these symptoms may be attributed to influenza, a cold, or other common infections, especially if malaria is not suspected. Conversely, in countries where malaria is frequent, residents often recognize the symptoms as malaria and treat themselves without seeking diagnostic confirmation ("presumptive treatment").

Physical findings may include:

• Elevated temperatures
• Perspiration
• Weakness
• Enlarged spleen
• Mild jaundice
• Enlargement of the liver
• Increased respiratory rate

A severe case of malaria can produce a host of life threatening signs and symptoms. It is also possible, with the P. vivax and P. ovale varieties, to relapse after months or years. According to WHO, children and pregnant women are at increased risk from malaria.

Several medications are available both to prevent malaria and to treat it. Initial treatment protocols call for medication on a set schedule for 48 hours. For patients with the parasites that may lead to relapse, a fourteen day course of treatment with medication is suggested by the CDC. Treatment for complications, and treatment for patients with special needs such as children or pregnant women can vary.

The current relief and reconstruction efforts in earthquake ravaged Haiti have exposed relief workers to malaria. Eleven cases were reported to the CDC in the first six weeks after the quake, including six members of the 82^nd Airborne Division. The CDC has posted recommendations for aid workers traveling to Haiti at its site.

Preventive measures can include preventive medication, the use of netting to isolate sleeping quarters, the use of insect repellants on clothing and bare skin and the use of insecticides to kill mosquitoes. DDT was the insecticide of choice until the 1960's and it was responsible for eliminating the native malarial threat from the United States. Both prevention and treatment currently are limited by resistance developed by certain Plasmodium strains to certain drug treatments, and resistance developed by mosquitoes to certain insecticides.

The following sites contain a great deal of additional information about malaria:

Centers for Disease Control malaria website

World Health Organization malaria website