Didier Drogba's brush with malaria is worrying for him and his fans, but would barely raise an eyebrow in his native Ivory Coast. Most of his countrymen will have suffered repeated episodes of the disease during their childhood, building up their immunity to the point where it troubles them only in the way that flu troubles us.

But malaria can be fickle, hiding away in the body for weeks, months or even years before emerging to trigger another episode of shivering, fever and joint pain. The parasite that enters the bloodstream through the mosquito's bite grows in the liver before emerging to infect the red blood cells, causing the fever.

The most common form of malaria, P. Falciparum, which accounts for 80 per cent of cases, may take up to 30 days to show symptoms after infection. But other forms such as P. Vivax can hide in the liver, causing illness months or years after infection. One in five infections with P. Vivax causes illness the year after the mosquito's bite.

Malaria should always be treated with respect, however mild the illness seems. The biggest threat is to the under-fives, of whom it kills almost one million a year, 90 per cent in sub-Saharan Africa.

More than 1,500 travellers from the UK acquire malaria every year. The most vulnerable are those who have never had the disease before. But even among those who grew up with it, the longer a person lives free of malaria, the greater their vulnerability to the illness when it strikes. Drogba will know that he must take care.