Risk factors for mortality from imported falciparum malaria in the United Kingdom over 20 years: an observational study OPEN ACCESS

Objectives To determine which travellers with malaria are at greatest risk of dying, highlighting factors which can be used to target health messages to travellers. Design Observational study based on 20 years of UK national data. Setting National register of malaria cases. Participants 25 054 patients notified with Plasmodium falciparum malaria, of whom 184 died, between 1987 and 2006. Main outcome measures Comparison between those with falciparum malaria who died and non-fatal cases, including age, reason for travel, country of birth, time of year diagnosed, malaria prophylaxis used. Results Mortality increased steadily with age, with a case fatality of 25/548 (4.6%) in people aged >65 years, adjusted odds ratio 10.68 (95% confidence interval 6.4 to 17.8), P<0.001 compared with 18–35 year olds. There were no deaths in the ≤5 year age group. Case fatality was 3.0% (81/2740 cases) in tourists compared with 0.32% (26/8077) in travellers visiting friends and relatives (adjusted odds ratio 8.2 (5.1 to 13.3), P<0.001). Those born in African countries with endemic malaria had a case fatality of 0.4% (36/8937) compared with 2.4% (142/5849) in others (adjusted odds ratio 4.6 (3.1 to 9.9), P<0.001). Case fatality was particularly high from the Gambia. There was an inverse correlation in mortality between region of presentation and number of cases seen in the region (R=0.72, P<0.001). Most delay in fatal cases was in seeking care. Conclusions Most travellers acquiring malaria are of African heritage visiting friends and relatives. In contrast the risks of dying from malaria once acquired are highest in the elderly, tourists, and those presenting in areas in which malaria is seldom seen. Doctors often do not think of these as high risk groups for malaria; for this reason they are important groups to target in pre-travel advice. Introduction Malaria is a major global infection, causing around 250 million clinical cases a year. It causes around 800 000 deaths a year, almost all in people living in poverty with limited access to healthcare, but it also causes avoidable deaths every year from imported malaria in non-endemic countries, mainly in people who are otherwise well. Travel to countries where malaria is endemic is increasing, and most general practitioners and acute care physicians are involved either in pre-travel advice or in diagnosing and treating cases on their return. The number of cases of imported falciparum malaria has increased over the past four years in the United Kingdom, 3 with 5774 reported cases in the period 2007–11. The UK, other European countries, and the United States also saw increases throughout the 1990s, which stabilised over the past decade. Case fatality has remained stable at around 1%, both in the UK and in other high income countries. Migrants frommalaria endemic countries and their descendants are at particular risk of acquiring malaria and make up over half of the UK’s imported malaria cases. Risk factors for acquiring malaria may, however, differ from risk factors for dying from malaria. Previously described risk factors associated with death from importedmalaria include older age, European origin, travel to east Africa, failure to take chemoprophylaxis, and delays in seeking medical care and in the diagnosis and treatment of suspected malaria. 10 12 13 Preventing malaria associated deaths is the ultimate aim in malaria prevention strategies, as those diagnosed and treated promptly generally make a full recovery. We reviewed in detail all deaths reported to be caused bymalaria infection in the UK over a 20 year period and compared them with all reported cases of malaria over the same period. The UK Correspondence to: C J M Whitty [email protected] No commercial reuse: See rights and reprints http://www.bmj.com/permissions Subscribe: http://www.bmj.com/subscribe BMJ 2012;344:e2116 doi: 10.1136/bmj.e2116 (Published 27 March 2012) Page 1 of 11