The correct answer is A. Tropical areas.
Malaria is a mosquito-borne infectious disease of humans caused by protozoan parasites of the genus Plasmodium. The disease is widespread in tropical and subtropical regions in a belt around the equator, where more than 90% of malaria cases occur.
The four Plasmodium species that cause malaria in humans are Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. Plasmodium falciparum is the most dangerous species, causing the most severe disease and the highest number of deaths.
Malaria is transmitted to humans through the bite of an infected female Anopheles mosquito. The mosquito bites a person and injects saliva into the wound. The saliva contains sporozoites, which are the infective form of the parasite. The sporozoites travel to the liver, where they mature into merozoites. The merozoites then invade red blood cells, where they multiply and cause the symptoms of malaria.
The symptoms of malaria include fever, chills, sweating, headache, muscle aches, and fatigue. In severe cases, malaria can cause anemia, coma, and death.
There is no vaccine for malaria. The best way to prevent malaria is to avoid mosquito bites. This can be done by using insect repellent, wearing long-sleeved shirts and pants, and sleeping under a mosquito net.
If you travel to an area where malaria is common, it is important to take preventive measures, such as taking malaria medication. You should also see a doctor if you develop any symptoms of malaria after returning from a trip.
The other options are incorrect because malaria is not more common in southern, eastern, or all over the world. Malaria is most common in tropical areas.