In epidemic and complex emergency situations, facilities for laboratory diagnosis may be either unavailable or so overwhelmed with the case-load that parasite-based diagnosis is impossible. In such circumstances, it is impractical and unnecessary to demonstrate parasites before treatment in all cases of fever. Once an epidemic of malaria has been confirmed, and if case numbers are high, treatment based solely on the clinical history is appropriate in most cases, using a full treatment course. However, parasite-based diagnosis is essential to:
• diagnose the cause of an epidemic of febrile illness,
• monitor and confirm the end of an epidemic,
• follow progress in infants, pregnant women, and those with severe malaria.
As the epidemic wanes, the proportion of fever cases investigated parasitologically can be increased. It is important to monitor the clinical response to treatment wherever possible, bearing in mind that other infections may also be present. In mixed falciparum/vivax epidemics, parasitaemia should be monitored in order to determine a species-specific treatment.