Current trends in malaria in Britain.

Malaria is already present in Britain with an average of 1843 cases reported annually in the last decade. The vast majority are imported cases who have acquired the infection elsewhere but have become ill in the United Kingdom. However, minute numbers are acquired either congenitally (transplacentally) from their infected (but often asymptomatic) mothers; or by blood transfusion, though this is almost wholly prevented now; or from mosquitoes, infected with malaria, which have succeeded in stowing away on aeroplanes in the tropics and surviving to bite man on emerging from the aircraft on landing. Two such cases, near Gatwick, have been reported in the UK but larger numbers have occurred around continental airports. Imported malaria has shown a complex pattern over the last three decades for there have been a series of temporary increases, from population movements due to wars and immigration, superimposed on longer term trends. The determinants of the levels of imported malaria are three: the level of transmission or endemicity in the tropical and subtropical areas where malaria is contracted; the amount of migration to endemic areas by British residents, that is exposure, and of travel to Britain by nationals of endemic areas; and, thirdly, the success or otherwise of attempts at prophylaxis by avoiding mosquito bites and taking antimalarial drugs. We can measure endemicity by epidemiological study in warm climate countries; exposure (to a first approximation) by means of travel statistics; and the effective risk (when preventive measures have been taken to a variable degree) by recording the number of cases actually detected in the UK.(ABSTRACT TRUNCATED AT 250 WORDS)