International insecticide brand Mortein claims that Nigeria contributes 23% of the world's malaria cases. Does the figure hit the mark?
In recent years, major insecticide brand Mortein is highly visible in anti-malaria campaigns in Nigeria. It often partners with state governments and agencies.
As part of these campaigns, the brand from British consumers goods giant Reckitt Benckiser issued a malaria factsheet. It states "Nigeria contributes 23% of the global malaria cases."
Does this claim line up with the latest estimates?
Missing links, missing data
In its factsheet, Mortein provided three references for its claim. Two of the links - for the Malaria Atlas Project and the Better Health Channel funded by the state government of Victoria, Australia - returned errors.
Africa Check asked Reckitt Benckiser's Nigeria office to clarify which sources they used, but they have not yet responded to the queries. (Note: This report will be updated when they do.)
The third source was a general malaria information webpage from the UK's National Health Service. A section referenced the World Malaria Report 2014 by the World Health Organisation (WHO).
Covering the year 2013, this report stated that Democratic Republic of Congo and Nigeria together accounted for 34% of malaria cases and 39% of deaths in the world. However, it did not explicitly provide each country's share.
The most recent WHO data on malaria - for 2016 - put Nigeria's share of total malaria cases at 27%, with its share of deaths even higher - at 30%.
Health facilities record fraction of cases
Determining the exact number of malaria cases in Nigeria is almost impossible, said Dr Olukemi Amodu of the Institute of Child Health at the University of Ibadan's medicine faculty.
Amodu, who is a member of the European Virtual Institute of Malaria Research, told Africa Check that the difficulty lies in inadequate reporting of the cases.
"Some people who suffer from malaria in Nigeria don't go to the hospital. They basically self-medicate and take care of themselves. So whatever number is recorded by health facilities is usually a fraction of the real situation."
For countries with poor surveillance systems and where routine data is considered unreliable, WHO estimates are the best bet for comparing countries' contribution to the global malaria burden. This Audu Mohammed, coordinator of Nigeria's National Malaria Elimination Programme, told Africa Check.
"Statistical formulas and epidemiological modelling are employed to get near accurate data in countries like Nigeria," Mohammed said.
"We collect data throughout the year; that is surveillance data we get from [public] health facilities. Sometimes we extrapolate. For instance, if you are getting data from a particular state for the first six to seven months and then they fall out and [health workers] go on strike, you [then] have to extrapolate."
'Best estimate that can be made'
The WHO uses a statistical model developed by the Malaria Atlas Project to arrive at estimates, Tolu Arowolo, the national professional officer for malaria in the WHO's Lagos office, told Africa Check.
The project's programme manager Mike Thorn explained that they estimate the parasite rate - the share of people infected with the malaria parasite - and the number of cases for each 5 km by 5 km grid in a country.
"Each estimate is accompanied by a confidence interval, which indicates how confident we are the estimates are correct," Thorn added. "We sum up estimates to give national totals, which is what we did for Nigeria."
Thorn added that the figures of Nigeria contributing 27% of global cases need to be taken with confidence intervals in mind.
"The figures of the number of cases we've attributed to Nigeria are the best estimate that can be made, given the data available to feed into the statistical models."
Surveillance system has improved
Arowolo, who is an epidemiologist, noted that Nigeria's share of the global malaria burden has varied, but that she "cannot categorically say whether or not Nigeria's share of global malaria cases has been 23%".
Nigeria's malaria surveillance system has improved in recent years and this has led to an increase in the number of reported cases, Arowolo said.
"A lot more centres are now contributing data. We are having high number of reported cases but it does not necessarily mean there are more cases of malaria. Our parasitemia level in the country shows that malaria is reducing. However, as more private health facilities begin to contribute malaria data, chances are that Nigeria's reported malaria cases will remain high."
Conclusion: Malaria factsheet understated Nigeria's malaria burden
A major insecticide brand stated in a factsheet that Nigeria contributes 23% of global malaria cases.
Accurate data on the exact number of malaria cases in Nigeria each year is hard to come by as surveillance is poor. To plug this gap, the World Health Organisation relies on a statistical model developed by the Malaria Atlas Project.
Employed for all countries where malaria occurs, the most recent iteration put Nigeria's share of global malaria cases at 27% in 2016, dropping from 29% in 2015.
This is the highest in the world by far.
This fact-check was researched by Allwell Okpi for Africa Check, the continent's leading fact-checking organisation. Read it on their website here. Follow Africa Check on Twitter @AfricaCheck.
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