Malaria in Sri Lanka: one year post-tsunami

Abstract

One year ago, the authors of this article reported in this journal on the malaria situation in Sri Lanka prior to the tsunami that hit on 26 December 2004, and estimated the likelihood of a post-tsunami malaria outbreak to be low. Malaria incidence has decreased in 2005 as compared to 2004 in most districts, including the ones that were hit hardest by the tsunami. The malaria incidence (aggregated for the whole country) in 2005 followed the downward trend that started in 2000. However, surveillance was somewhat affected by the tsunami in some coastal areas and the actual incidence in these areas may have been higher than recorded, although there were no indications of this and it is unlikely to have affected the overall trend significantly. The focus of national and international post tsunami malaria control efforts was supply of antimalarials, distribution of impregnated mosquito nets and increased monitoring in the affected area. Internationally donated antimalarials were either redundant or did not comply with national drug policy, however, few seem to have entered circulation outside government control. Despite distribution of mosquito nets, still a large population is relatively exposed to mosquito bites due to inadequate housing. There were no indications of increased malaria vector abundance. Overall it is concluded that the tsunami has not negatively influenced the malaria situation in Sri Lanka.

Figure 1

Parasite incidence by district pre- and post-tsunami. Monthly parasite incidence of P. falciparum and P. vivax malaria combined in 2004 (red bars) and 2005 (blue bars). Overlapping bars color purple. Bars in the legend represent 1 case per 10,000 persons per month. Numbers indicate the percentage change of January – December 2005 as compared to January – December 2004 for each district.

Figure 2

Monthly parasite and blood smear examination incidence patterns. Monthly parasite incidence patterns of P. falciparum and P. vivax malaria combined per 1000 population (thick red line) and 12 month moving average (thin red line), blood smears examined per 1000 population (thick black line) and 12 month moving average (thin black line), and proportion of blood smears positive for malaria (thick blue line) and 12 month moving average (thin blue line) from January 1995 to December 2005 in Sri Lanka. Ninety-five % confidence areas are indicated for one-month ahead prediction of time series for January – December 2005, using fixed trends found in the period April 2000 – December 2004 (in grey).