- Email: [email protected]
New global estimates of malaria deaths
Correspondence
New global estimates of malaria deaths
www.thelancet.com Vol 380 August 11, 2012
Murray and colleagues World Malaria Report 2011
1 000 000 Number of malaria deaths
Christopher Murray and colleagues’ paper (Feb 4, p 413)1 estimating the number of malaria deaths worldwide, 1980–2010, invites caution in its interpretation. Murray and colleagues estimate that there were 1 238 000 malaria deaths worldwide in 2010, compared with WHO’s estimate of 655 000.2 However, wide uncertainty ranges accompany both the Murray and colleagues and WHO estimates, and with one exception— for deaths in people older than 5 years in Africa—these ranges overlap, so the estimates cannot be regarded as significantly different (figure). Murray and colleagues’ finding of a large number of deaths in people older than 5 years in Africa, in relation to those younger than 5 years (figure), is unexpected in stably endemic areas, since partial immunity to malaria generally develops at an early age, protecting most older children and adults against severe disease and death. In Africa, much lower adultto-child death ratios have been found when malaria deaths are confirmed microscopically.3 For African countries, Murray and colleagues did not use microscopically confirmed malaria but relied on verbal autopsy. They justify their approach by referring to earlier validation exercises in six study sites. However, five of those sites had little or no malaria transmission during the validation period, and in the one stably malariaendemic site (Dar es Salaam) the quality of microscopic diagnosis, used as the gold standard to confirm malaria-attributable deaths, has been challenged.4 Moreover, other studies have found substantial overdiagnosis of severe malaria in adults attending the same health facilities.5 This level of overdiagnosis of malaria in the records of the gold-standard health facilities and, consequently, in verbal autopsies, would lead to a substantial overestimate of adult malaria deaths.
1 200 000
800 000 600 000 400 000 200 000 0
<5 years
≥5 years
<5 years
Africa
≥5 years Outside Africa
Figure: Number of malaria deaths in 2010, by age group and region, as estimated by Murray and colleagues1 and in the World Malaria Report 20112
Attempts to refine estimations are welcome, but there remain many inherent uncertainties in any approach to produce precise estimates of malaria mortality. The global malaria community must increase efforts to support malaria-endemic countries in improving diagnostic testing, surveillance, vital registration, and routine health information systems, which will gain importance as we scale up malaria control, and move towards elimination and eventual eradication of malaria. We declare that we have no conflicts of interest.
*Michael Lynch, Eline Korenromp, Thom Eisele, Holly Newby, Rick Steketee, S Patrick Kachur, Bernard Nahlen, Steven Yoon, John MacArthur, Robert Newman, Richard Cibulskis [email protected] WHO, 1211 Geneva, Switzerland (ML, RN, RC); Global Fund to Fight AIDS, Tuberculosis and Malaria, Geneva, Switzerland (EK); Tulane University, New Orleans, LA, USA (TE); UN International Children’s Emergency Fund, New York, NY, USA (HN); Program for Appropriate Technology in Health, Seattle, WA, USA (RS); US Centers for Disease Control and Prevention, Atlanta, GA, USA (SPK, SY, JM); and United States Agency for International Development, Washington, DC, USA (BN) 1
2
3
Murray CJL, Rosenfeld LC, Lim SS, et al. Global malaria mortality between 1980 and 2010: a systematic analysis. Lancet 2012; 379: 413–31. WHO. World malaria report 2011. Geneva: World Health Organization, 2011. http://www. who.int/malaria/world_malaria_report_2011/ en (accessed July 24, 2012). Reyburn H, Mbatia R, Drakeley C, et al. Association of transmission intensity and age with clinical manifestations and case fatality of severe Plasmodium falciparum malaria. JAMA 2005; 293: 1461–70.
4
5
Kahama-Maro J, D’Acremont V, Mtasiwa D, Genton B, Lengeler C. Low quality of routine microscopy for malaria at different levels of the health system in Dar es Salaam. Malaria J 2011; 10: 332. Makani J, Matuja W, Liyombo E, Snow RW, Marsh K, Warrell DA. Admission diagnosis of cerebral malaria in adults in an endemic area of Tanzania: implications and clinical description. QJM 2003; 96: 355–62.
Two highly publicised papers1,2 claim unexpectedly large numbers of deaths from malaria in adults. Both studies are based mainly on verbal autopsy estimates. In the first study,1 36% of malaria deaths in India were estimated to have occurred in adults older than 45 years. In the latest report by Christopher Murray and colleagues,2 of the model-predicted global adult malaria mortality between 1980 and 2010, about 55% of the deaths were in those aged 15–49 years, 30% were aged 50–69 years, and 15% were 70 years or older. This large malaria mortality in older patients does not accord with our clinical experience. We have helped to do prospective hospital-based studies on severe malaria in Thailand, Vietnam, Burma, Bangladesh, Indonesia, India, and Mozambique.3,4 Of 2991 prospectively studied, unselected adult patients with strictly defined severe malaria who were admitted consecutively to the hospital wards in each study site,3,5 580 (19·4%) died: 67 deaths were in patients aged 50 years or older, of whom only four were 70 years or older (figure). Thus, 11·7% of confirmed
Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/
559
New global estimates of malaria deaths
www.thelancet.com Vol 380 August 11, 2012
Murray and colleagues World Malaria Report 2011
1 000 000 Number of malaria deaths
Christopher Murray and colleagues’ paper (Feb 4, p 413)1 estimating the number of malaria deaths worldwide, 1980–2010, invites caution in its interpretation. Murray and colleagues estimate that there were 1 238 000 malaria deaths worldwide in 2010, compared with WHO’s estimate of 655 000.2 However, wide uncertainty ranges accompany both the Murray and colleagues and WHO estimates, and with one exception— for deaths in people older than 5 years in Africa—these ranges overlap, so the estimates cannot be regarded as significantly different (figure). Murray and colleagues’ finding of a large number of deaths in people older than 5 years in Africa, in relation to those younger than 5 years (figure), is unexpected in stably endemic areas, since partial immunity to malaria generally develops at an early age, protecting most older children and adults against severe disease and death. In Africa, much lower adultto-child death ratios have been found when malaria deaths are confirmed microscopically.3 For African countries, Murray and colleagues did not use microscopically confirmed malaria but relied on verbal autopsy. They justify their approach by referring to earlier validation exercises in six study sites. However, five of those sites had little or no malaria transmission during the validation period, and in the one stably malariaendemic site (Dar es Salaam) the quality of microscopic diagnosis, used as the gold standard to confirm malaria-attributable deaths, has been challenged.4 Moreover, other studies have found substantial overdiagnosis of severe malaria in adults attending the same health facilities.5 This level of overdiagnosis of malaria in the records of the gold-standard health facilities and, consequently, in verbal autopsies, would lead to a substantial overestimate of adult malaria deaths.
1 200 000
800 000 600 000 400 000 200 000 0
<5 years
≥5 years
<5 years
Africa
≥5 years Outside Africa
Figure: Number of malaria deaths in 2010, by age group and region, as estimated by Murray and colleagues1 and in the World Malaria Report 20112
Attempts to refine estimations are welcome, but there remain many inherent uncertainties in any approach to produce precise estimates of malaria mortality. The global malaria community must increase efforts to support malaria-endemic countries in improving diagnostic testing, surveillance, vital registration, and routine health information systems, which will gain importance as we scale up malaria control, and move towards elimination and eventual eradication of malaria. We declare that we have no conflicts of interest.
*Michael Lynch, Eline Korenromp, Thom Eisele, Holly Newby, Rick Steketee, S Patrick Kachur, Bernard Nahlen, Steven Yoon, John MacArthur, Robert Newman, Richard Cibulskis [email protected] WHO, 1211 Geneva, Switzerland (ML, RN, RC); Global Fund to Fight AIDS, Tuberculosis and Malaria, Geneva, Switzerland (EK); Tulane University, New Orleans, LA, USA (TE); UN International Children’s Emergency Fund, New York, NY, USA (HN); Program for Appropriate Technology in Health, Seattle, WA, USA (RS); US Centers for Disease Control and Prevention, Atlanta, GA, USA (SPK, SY, JM); and United States Agency for International Development, Washington, DC, USA (BN) 1
2
3
Murray CJL, Rosenfeld LC, Lim SS, et al. Global malaria mortality between 1980 and 2010: a systematic analysis. Lancet 2012; 379: 413–31. WHO. World malaria report 2011. Geneva: World Health Organization, 2011. http://www. who.int/malaria/world_malaria_report_2011/ en (accessed July 24, 2012). Reyburn H, Mbatia R, Drakeley C, et al. Association of transmission intensity and age with clinical manifestations and case fatality of severe Plasmodium falciparum malaria. JAMA 2005; 293: 1461–70.
4
5
Kahama-Maro J, D’Acremont V, Mtasiwa D, Genton B, Lengeler C. Low quality of routine microscopy for malaria at different levels of the health system in Dar es Salaam. Malaria J 2011; 10: 332. Makani J, Matuja W, Liyombo E, Snow RW, Marsh K, Warrell DA. Admission diagnosis of cerebral malaria in adults in an endemic area of Tanzania: implications and clinical description. QJM 2003; 96: 355–62.
Two highly publicised papers1,2 claim unexpectedly large numbers of deaths from malaria in adults. Both studies are based mainly on verbal autopsy estimates. In the first study,1 36% of malaria deaths in India were estimated to have occurred in adults older than 45 years. In the latest report by Christopher Murray and colleagues,2 of the model-predicted global adult malaria mortality between 1980 and 2010, about 55% of the deaths were in those aged 15–49 years, 30% were aged 50–69 years, and 15% were 70 years or older. This large malaria mortality in older patients does not accord with our clinical experience. We have helped to do prospective hospital-based studies on severe malaria in Thailand, Vietnam, Burma, Bangladesh, Indonesia, India, and Mozambique.3,4 Of 2991 prospectively studied, unselected adult patients with strictly defined severe malaria who were admitted consecutively to the hospital wards in each study site,3,5 580 (19·4%) died: 67 deaths were in patients aged 50 years or older, of whom only four were 70 years or older (figure). Thus, 11·7% of confirmed
Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/
559