October 19, 2021
Malaria is an infectious disease transmitted by mosquitoes and caused by parasitic protozoa of the genus Plasmodium. The most common symptoms are fever, fatigue, vomiting and headache. In severe cases it can cause jaundice, seizures, coma or death. Symptoms begin to manifest between 10 and 15 days after the bite. If left untreated, the disease can recur months later. A new infection usually causes milder symptoms. However, this partial immunity can disappear within months to years if the person is not continually exposed to the disease. The disease is usually transmitted by the bite of an infected female Anopheles mosquito. The sting introduces the parasites present in its saliva into the host's circulatory system. Parasites are deposited in the liver, where they develop and reproduce. There are five species of Plasmodium that can infect humans. Most deaths are caused by P. falciparum. The species P. vivax, P. ovale, and P. malariae generally cause less severe forms of malaria that are rarely fatal. The species P. knowlesi rarely causes the disease in humans. The diagnosis of malaria is based on microscopic blood tests that confirm the presence of the parasite or through rapid diagnostic tests that detect the presence of antigens in the blood. There are also diagnostic techniques that use the polymerase chain reaction to detect the parasite's DNA, although its use in regions where the disease is endemic is uncommon due to its high cost and complexity. Disease transmission can be fought through prevention of mosquito bites. The most common prevention measures are the use of mosquito nets or insect repellent and eradication measures, such as the use of insecticides or the drainage of stagnant water. Various drugs to prevent malaria are available for travelers traveling to countries where the disease is endemic. In high-incidence regions, administration of sulfadoxine/pyrimethamine is recommended for younger children and pregnant women after the first trimester. There is no effective vaccine against malaria, although there are efforts to develop one. The recommended treatment for malaria is an artemisinin plus a second antimalarial. Antimalarials are usually mefloquine, lumefantrine or sulfadoxine/pyrimethamine. When artemisinin is not available, quinine with doxycycline can be used. In areas where the disease is common, it is recommended that the presence of the disease be confirmed before starting treatment due to concerns about increasing drug resistance. Several parasites have developed resistance to a number of antimalarials, such as quinine resistant P. falciparum and artemisinin resistance in various parts of Southeast Asia. Malaria is endemic in tropical and subtropical regions due to abundant rainfall, hot temperature and large amount of stagnant water, which provides ideal habitats for mosquito larvae. The disease is spread throughout the tropical and subtropical regions of the planet along a wide band around the equator, which includes much of sub-Saharan Africa, Asia and Latin America. In 2016, there were 216 million cases of malaria worldwide, estimated to have been the cause of 731,000 deaths. About 90% of cases and deaths occurred in Africa. Between 2000 and 2015 the incidence of the disease decreased by 37%. Malaria is generally associated with poverty and has a major negative impact on economic development. In Africa, the disease is estimated to result in losses of $12 billion a year due to health care costs, job losses and impact on tourism.