Published on 16th November 2012.
We now have a 3rd set of post-distribution data for Ntcheu District, Malawi which extends our malaria case rate data from June through to September.
- The incidence of malaria in July, August and September 2012 were 41%, 47% and 35% lower than in the corresponding months of the prior year.
- As a result of the 6 month post-distribution survey 10 areas were identified as having lower net hang-up and additional, structured malaria education and hang-up activities took place in late September with the aim of raising levels from an average of 84% to 94+%.
Since the universal coverage net distribution completed in February 2012 there has been a
consistent and sustained reduction in the incidence of malaria (compared to the same month in the prior year) of between 35 and 55%.
The last three months of malaria case rate data are particularly important because the data we are comparing for these months and the same months in 2011 are both based on Rapid Diagnostic Testing Kit (RDTK) blood diagnosis, whereas (as explained in the previous update, below) the 2010 data were based on observation.
The new data shows that the incidence of malaria for July, August and September were 41%, 47% and 35% lower in 2012 than in 2011. The updated graph and data sheets illustrate this fact.
Published on 24th July 2012.
We now have two sets of post-distribution data following the December 2011 to February
2012 distribution of 270,000 nets in
Ntcheu District, Malawi and the results are strong.
- Malaria rates in March to June 2012 are already 50%, 45%, 40% and 40% lower than in the
corresponding months in 2011. See:
Malaria case rate data
- Six months post-distribution a survey of 7,657 households
and 15,768 nets showed a hang-up (usage) level of 90% and the percentage of nets in a very good condition is 99% (ninety nine). See:
Six month surveys
We will continue to collect and publish monthly malaria data and hope to see a continued and sustained decline in malaria rates.
1. Malaria case rates
Raw malaria case rate data for the period March to June 2012 shows a reduction of
malaria cases of 60%, 54%, 50% and 50% for March, April, May and June respectively
compared to the same months in the prior year. However, the March-June 2011 data
was based on clinical observation whereas the March-June 2012 data was based on
Rapid Diagnostic Testing Kit (RDTK) blood diagnosis. Data in the non-rainy season
strongly indicates clinical observation overestimates malaria cases by 40-50%. This
is concluded from comparing data from Jul to Nov 2011 (RDTK basis) with Jul to Nov
2010 data (clinical observation). In the rainy season there is limited data to draw
conclusions but data for Dec 2011-Jan 2012 compared to Dec 2010-Jan 2011 suggests
the over-estimate due to clinical observation in these months may be significantly
lower and in the range 5-15%. This has support from anecdotal evidence (we are trying
to collect data from other studies) which suggests 'false positives' decline in
the rainy season as a high percentage of those with 'malaria and fever type symptoms'
do indeed have malaria. Assessing the likely level of falsely observed malaria cases
is important as without doing so the malaria case rate decline would be over-estimated.
As the March-June 2012 data falls within the peak malaria season, we estimate the
actual malaria fall is some 10 percentage points less or 50%, 45%, 40 and 40% respectively.
Data has been collected from all 37 of the health centres in Ntcheu District. Four
of these data centres have unreliable data and have been excluded.
For the April to June data we are waiting for five health centres to report and
we will update this blog post and the attached data when that information has been
received. We do not expect it to markedly change the percentages reported above.
2. Net hang-up and condition
Between 200 and 250 households in each of the 37 health centre catchment areas were
surveyed to assess net hang-up and condition. In total, 7,606 households and 15,681
nets (6% of those distributed) were visited and assessed. The data is currently
being double checked and some numbers may change very slightly.
A 90% hang-up level is very high compared with many other studies that typically
report hang-up between 50-80%. We put this down to a combination of:
i) detailed pre-distribution registration survey work carried out in advance of
the net distribution with which there were high levels of community involvement
ii) thorough malaria education in advance of, and during, the distribution process;
iii) Malawians have a reputation for responding positively to community-wide initiatives.
Concern Universal staff deserve huge credit for their project management abilities.
1% of nets were missing, the predominant reason being nets had been taken by schoolchildren
or relatives sleeping elsewhere. This is believable. We do not believe any or many
The 9% of nets not hung are clustered in 10 areas. We initially thought this might
be because these areas were at higher altitude with lower mosquito population levels.
This is not the case as some areas are low lying. The 13% to 23% of 'nets present
but not hung' is currently being investigated. The 10 areas are those with lower
levels of malaria, compared to other areas in the district, and one hypothesis is
that some community members in these areas perceive there to be very low or no risk
of malaria outside the peak malaria period that coincides with the rainy season.
Malaria is still present in these areas however and, if low/no perceived risk is
found to be the case, another round of malaria education may be an appropriate action.
Net condition six months post-distribution is exceptionally strong. 99% are in 'very
good' condition (fewer than two holes of 2 cms or smaller) and 1% are in 'OK' condition
(fewer than 10 holes). We would expect nets to be in very good condition after six
months but this is an exceptionally high level. The condition of the net is a subjective
assessment. It is possible there is bias introduced by those carrying out the survey.
The following operating elements were put in place to mitigate against inaccurate
i) training was given to those carrying out the survey to ensure
consistency of the counting of the number and size of holes;
ii) Concern Universal staff were involved in and supervised the survey work and
selected to carry out this work with only a subset of the government's health staff,
Health Surveillance Assistants (HSAs), known to be the most reliable;
iii) emphasis was placed during training on accurate recording of net condition
and other data as a) false data would not help our collective understanding of the
condition of the net stock and b) spot checks would occur to check data accuracy;
iv) those carrying out the survey work had nothing to gain by providing inaccurate
assessments, not even significant time saved in carrying out the assessments as
households had to sign the survey forms;
vi) data verification through spot checks of pre-distribution registration information,
gathered by HSAs, showed the data collected was exceptionally accurate.
We believe the data is reliable. We will however be conducting some spot checks
to test the accuracy of the data.
We expect the condition of the net stock to decline over time and we would expect
to see more of a decline through months 12 and 18. Over this period in particular,
malaria education messaging will address net care so as to encourage as high a level
of net condition as possible.
It should be noted that even with a number of holes, long-lasting insecticide treated
nets (LLINs) remain almost completely effective, often phrased as '99% effective'.
This is because mosquitoes land on a net and then migrate to a hole, and in so doing
pick up insecticide which can cause knock-down, rather than executing an aerobatic
manoeuvre and passing directly through a hole.