Malaria: Getting Better, but Still a Long Way To Go
Although extraordinary efforts have led to decreases in cases of malaria, the number of cases remains very high. It is estimated that 3.3 billion people live in areas that put them at risk of malaria, and that the risk is high (defined as having an incidence of > 1 per 1000 population annually) for 1.2 billion of these. An estimated 198 million cases occurred in 2013, resulting in approximately 584,000 deaths. The World Health Organization (WHO) Africa region accounted for 90% of the deaths; children 5 years of age accounted for 78% of all deaths.
Vector control activities have significantly increased so that by 2013, 49% of at-risk populations in sub-Saharan Africa had access to insecticide-treated mosquito nets in their household, an increase from only 3% in 2004. WHO estimated that, by the end of 2014, the number of such nets delivered to countries in the region since 2012 would total 427 million. On the other hand, the proportion of at-risk populations who were protected by the use of indoor residual spraying decreased in sub-Saharan Africa from 11% in 2010 to 7% in 2013. Globally, only 4% were protected. Unfortunately, vector resistance to insecticides is increasingly widespread.
Thirty-five countries have adopted intermittent preventive treatment in pregnancy and, in 2013 in those countries, 57% of pregnant women received at least one dose. However, only 17% received the recommended greater than three doses in the nine countries reporting this information. WHO has recommended to 13 countries that they institute seasonal malaria chemoprophylaxis for infants and children younger than 5 years of age, but only six had done so for children and only one was administering prophylaxis to infants by 2013.
DIAGNOSIS, TREATMENT, RESISTANCE
More than 160 million rapid diagnostic tests were distributed by national malaria control programs in 2013 — an increase from less than 200,000 in 2005. The WHO Africa Region accounted for 83% of these.
Artemisinin-based combination therapy (ACT) was national policy by the end of 2013 in 79 of the 88 countries in which Plasmodium falciparum infection is endemic. In that year, enough ACT was available in public heath facilities to treat more than 70% of malaria cases. Nonetheless, WHO estimates that only 9-26% of children with malaria received ACT.
Resistance of P. falciparum to artemesinin is present in Cambodia, Laos, Myanmar, Thailand, and Vietnam. Furthermore, in areas along the border between Cambodia and Thailand, P. falciparum is now resistant to most available antimalarials. The emergence of this resistance is likely the result of artemisinin monotherapy, which is contraindicated. Fortunately, at the urging of WHO, there has been a rapid decease in the number of countries that allow marketing of oral artemisinin-based monotherapies, so that this was allowed in only 8 countries as of November 2014. India, where 24 pharmaceutical companies still market oral artemisinin-based monotherapies, is an important outlier.
A total of 64 countries are on track to meet the Millennium Development Goal target of reversing the incidence of malaria, and 55 of these are on track to meet Roll Back Malaria and World Health Assembly targets of reducing malaria case incidence rates by 75% by 2015. However, these countries are not the ones with the largest at-risk populations — these 55 countries accounted for only 13 million (6%) of the total estimated cases of 227 million in 2000. Nonetheless, the mean malaria prevalence in children 2–10 years of age decreased by almost one-half from 26% to 14% in 2000 and 2013, respectively. The total number of infected individuals in Central Africa decreased from 173 million to 128 million during this time period.
Estimates of global malaria indicate that between 2000 and 2013, despite a 25% increase in at-risk population (43% in the WHO Africa region), the number of cases decreased from 227 million to 198 million, representing a 30% decrease in cases per 1000 population (34% in the WHO Africa region). There was a concomitant decrease in mortality such that at the current rate, it is projected that a global 55% decrease relative to 2000 will be reached in 2015, with a 62% decrease in the WHO Africa region. Overall, an estimated 4.3 million deaths were averted between 2000 and 2013, and 92% of these were in children younger than 5 years of age in sub-Saharan Africa.
This WHO report is simultaneously encouraging and disturbing. While important progress has been made, the path ahead is long and arduous, made all the more so by inadequate resources. Thus, although there was a three-fold increase in funding for malaria control between 2005 and 2013, there remains significant underfunding.
While significant progress has been made in the control of malaria, the number of cases remains huge — an estimated 198 million cases and 584,000 deaths in 2013.
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