April 25 is Malaria Day.

What is malaria?

Malaria is a serious, sometimes fatal, disease which is transferred to humans from the bite of a malaria-infected mosquito.

What are the symptoms?

Symptoms include fever and flu-like illness with headaches, muscle aches, shivering and lethargy. Nausea, vomiting, diarrhoea, anaemia and jaundice can also occur. If not properly treated, infection with the type of malaria known as Plasmodium falciparum may cause kidney failure, seizures, coma and death.

Where does it occur?

Malaria occurs in over 100 countries. More than 40 percent of world's population lives at risk from it. Malaria is present in large areas of Central and South America, Africa, the Indian subcontinent, southeast Asia, the Middle East, and Oceania.

Ninety percent of deaths due to malaria occur in sub-Saharan Africa, mostly among young children. Malaria kills an African child every 30 seconds.

How many cases of malaria are there each year?

The U.N. World Health Organisation (WHO) estimates that there are 300-500 million cases of malaria each year, killing more than a million people annually.

New estimates published by scientists in early 2005, however, indicate that the number is even higher. The figures, published in the science journal Nature, are almost twice those of the WHO. The scientists estimated there were 365 million cases of malaria in Africa alone in 2002 and claimed that Plasmodium falciparum -- the deadliest form of the disease -- affects some 500 million people a year worldwide.

An estimated 700,000-2.7 million people die of malaria each year, 75 per cent of them African children. Over 80 percent of malaria deaths occur in Africa where around 66 percent of the population are thought to be at risk.

In 2002, malaria was the fourth cause of death in children in developing countries, after perinatal conditions (conditions occurring around the time of birth), lower respiratory infections (pneumonias), and diarrhoeal diseases.

How is it treated?

In recent years drug-resistant strains of malaria have spread, rendering once effective -- and cheap -- anti-malarial drugs almost useless. Drug-resistant strains of Plasmodium falciparum now occur in 90 percent of cases in Africa.

A new treatment called artemisinin combination therapy, or ACT, has been introduced and is slowly replacing the obsolete anti-malarial drugs.

In some countries, the disease may account for as much as 40 percent of public health expenditure, 30-50 percent of inpatient admissions, and up to 50 percent of outpatient visits.