Emergency preparedness for malaria epidemics should be part of the general organization of emergency health services, which in turn should be an integral part of every health system (Brès, 1986). Similarly, preparedness plans for malaria epidemics and for emergency health services should be included in the National Disaster Preparedness Plan, particularly in areas at recognized risk of natural disasters, such as earthquakes, hurricanes, cyclones or floods. It is obvious that in areas subject to a recurrent risk of malaria epidemics, such services should devote particular attention to the specific requirements to be met in dealing with them effectively.

Preparedness for malaria epidemics should be based on an understanding of the epidemiology of malaria and of the epidemic risk factors. The more complete that understanding and the more developed the information system and the monitoring of risk factors, the higher will be the level of preparedness, the more accurate the forecasting and the more adequate the preventive response. An adequate monitoring system will allow between one and three months to implement preventive measures, including the strengthening of diagnosis and treatment facilities. Even a major disaster resulting in widespread destruction of houses and immediate exposure of people, such as hurricane Flora in Haiti, produced a malaria epidemic only after one and half months. The immediate implementation of preventive measures should be possible if the appropriate manpower, supplies, equipment and logistical arrangements are ready to be brought into action. Malaria preparedness should therefore include the identification of these resources and the required mechanisms for their rapid mobilization. In general, the establishment of stocks of insecticides and spraying equipment is not advisable. The building-up of sufficient reserves in a neighbouring programme for vector control, or even for some other form of pest control, is more appropriate.

As mentioned above, epidemic risk tends to increase and decrease, often with a five to 10 year periodicity. It would therefore be wise to streamline epidemic preparedness as the risk time approaches, building-up the required stocks of insecticides and drugs, organizing training, etc. For example, in some arid areas of north-western India, epidemics normally follow early and abundant rains, particularly when they occur after a very dry year. A simplified example for preparedness in areas where epidemics are expected to follow a five-year cycle would be to order equipment and insecticides in the third year following an epidemic. Then, in September of a very dry year, preparations should be started and if, in the following year, the rains start early (May-June) and continue during July, spraymen should be recruited and trained in July or early August, so that they can start spraying in the first half of August if the rains continue.

11.1 Preventive measures

When a high risk is detected, the first consideration in the selection of a preventive strategy is whether the epidemic should be completely prevented by total coverage with vector-control measures, or whether a more conservative policy should be adopted so as to prevent mortality and incapacity by providing accessible facilities for early diagnosis and prompt treatment everywhere. Transmission control is then restricted to the reduction of the epidemic wave in the most vulnerable areas. The choice between these policies, or any combination of them in different areas, should be guided by:

• the expected impact of the epidemic based on the immune status of the population, the risk of P. falciparum, drug resistance, etc.;
• the feasibility of successfully implementing the different alternatives;
• the possibility of maintaining the capacity to prevent future waves.

The much greater appeal of complete prevention of an epidemic often leads to the choice of vector-control campaigns while neglecting the strengthening of case-management facilities. If vector control is not successful, the epidemic may still occur and have a severe impact. In general, it may be advisable to attempt full epidemic prevention only when there is a good infrastructure capable of coping with the disease, whatever form it might take.

Technically, the preventive measures will be the same as those discussed under epidemic control, but it will be possible to plan and implement them more effectively, without the hurry and improvisation often seen in epidemic control.

In the case of P. vivax epidemics, it may be advisable to implement mass antirelapse treatment in the winter or early spring, giving all cases from the previous season full primaquine treatment. An important consideration in the selection of this intervention is whether or not P. vivax cases were treated with primaquine and the length of that treatment, i.e., five or 14 days. If winter-spring treatment is contemplated, it should be decided whether to attempt courses of 14 days or the generally more feasible eight weekly doses.

As mentioned above, preventive measures will depend on the degree of preparedness and the time between the detection of risk and the expected beginning of the epidemic. When that time is short and preparations for vector control have not been completed, the only choice will be the strengthening of case-management capacity, as it was in the pre-DDT era.