Conceived and designed the experiments: ZCS HNP NRM MHD SOK MIM. Performed the experiments: ZCS MIM. Analyzed the data: ZCS HNP MIM. Contributed reagents/materials/analysis tools: ZCS HNP NRM SOK. Wrote the paper: ZCS HNP NRM MHD SOK MIM. Collected data: ZCS MHD.
Effective surveillance for infectious diseases is an essential component of public health. There are few studies estimating the costeffectiveness of starting or improving disease surveillance. We present a costeffectiveness analysis the Integrated Disease Surveillance and Response (IDSR) strategy in Africa.
To assess the impact of the IDSR in Africa, we used pre and post IDSR meningococcal meningitis surveillance data from Burkina Faso (1996–2002 and 2003–2007). IDSR implementation was correlated with a median reduction of 2 weeks to peak of outbreaks (25^{th} percentile 1 week; 75^{th} percentile 4 weeks). IDSR was also correlated with a reduction of 43 meningitis cases per 100,000 (25^{th}–40: 75^{th}129). Assuming the correlations between reductions in time to peak of outbreaks and cases are related, the costeffectiveness of IDSR was $23 per case averted (25^{th}$30; 75^{th}  cost saving), and $98 per meningitisrelated death averted (25^{th}$140: 75^{th} – cost saving).
We cannot absolutely claim that the measured differences were due to IDSR. We believe, however, that it is reasonable to claim that IDSR can improve the costeffectiveness of public health surveillance.
More than 1.5 million children die each year in subSaharan Africa, from diarrhea, malaria, measles, meningitis, respiratory infections, yellow fever, and HIV/AIDS
Although considerable progress had been achieved with implementation of the IDSR strategy (see
To model the costeffectiveness of IDSR, we used data from Burkina Faso because that country had fully established IDSR leadership and structures at the national level by 2002, with implementation at regional and district levels in 2003. Burkina Faso had data, collected using the IDSRsupported surveillance systems, on several meningitis outbreaks.
The nature of disease surveillance systems makes it impossible to have a randomly controlled experiment to measure the impact of IDSR on public health outcomes. We were unable to readily collect comparable data from another country (e.g., one without IDSR systems, or one that implemented IDSR systems after Burkina Faso), and thus we were unable to conduct a comparison between countries. We therefore relied on observational (beforeandafter) data from outbreaks of meningococcal meningitis to assess the possible impact of IDSRrelated activities in Burkina Faso. We assumed that any correlations between the start of IDSR activities, which includes both surveillance and response to disease activity detected, and changes in the epidemiology of meningitis outbreaks were due primarily to IDSR. With this assumption, we calculated, on an outbreak basis, costs per case, per death and per
As most health care and IDSR activities in Burkina Faso are funded by the government, we took the perspective of the governmentfunded public health care system (i.e., we only recorded costs and savings incurred by the national government); costs incurred by households were not included. All cost data were recorded in local currency values and then converted into US dollar values using the mean annual exchange rate. We used the general consumer price index from Burkina Faso
We obtained from the WHO MultiDiseases Surveillance Center in Ouagadougou annual population data and district level reports of weekly meningitis cases and deaths from Burkina Faso for the years 1996–2007 (see
We sorted the data into two groups: before (1996–2002) and after (2003–2007) IDSR implementation at district level. During this study period, all meningitis outbreaks in Burkina Faso only occurred between January and June (23week period). For each group, we examined the weekly incidence rates in relation to the WHO recommended alert threshold (5 cases per 100,000) and epidemic threshold (10 cases per 100,000)
For each group of outbreaks before and after IDSR implementation (start 2003), we calculated the median, 25^{th} and 75^{th} percentile for each of the following health outcomes: weekly and cumulative total incidence, mortality and sequelae.
We first plotted the average weekly incidence rates over the time period studied and the median weekly incidence and mortality before and after IDSR implementation over the 23week period of meningitis outbreaks. We then compared the health outcomes (i.e., incidence, mortality, time to peak and time to reach a set percentile of total cases per outbreak) using the MannWhitney test using SAS statistical software version 9.1 (SAS Institute Inc., Cary, NC, USA). In 1996 there was an “unusually” large epidemic of meningitis in Burkina Faso. We therefore examined the influence of 1996 data on the IDSR effectiveness measures by rerunning the analyses excluding 1996 data.
As IDSR encompasses a deliberate response factor, it is plausible that vaccine imports may increase postIDSR implementation. In order to assess potential correlation between IDSR implementation and meningococcal vaccine importation, we obtained estimates of the doses of vaccine imported by the Burkina Faso government from the WHO International Consultative Group, UNICEF, and GlaxoSmithKline Biologicals. Vaccine data were also collected from the WHO disease outbreak website (
Doses per 100,000 population in whole country (excluding 1996 data); Doses per 100,000 population in districts where outbreaks occurred (including 1996 data); and, doses per 100,000 population in districts where outbreaks occurred (excluding 1996 data). To check for autocorrelation, we calculated the DurbinWatson statistic for each regression.
We used the costs of IDSRrelated activities reported in our previous study [26; see also
We also obtained direct medical care costs incurred by the government to treat a patient with meningitis relatedillness at district health facility ($53) and regional hospital ($71) during the 2002 epidemic situation (unpublished data, Ministry of Health, Burkina Faso; see
Assuming that any measured differences between health outcomes (i.e., after IDSR minus before IDSR) are due to IDSR, we calculated the costeffectiveness in net cost (in dollars) per outcome averted using the following general formula:
We used the above formula to calculate the costeffectiveness ratios for the median, 25^{th}, and 75^{th} percentiles differences in cases, deaths or sequelae averted before and after IDSR. The median (25^{th}, 75^{th}) cost effectiveness ratio was calculated using the median (25^{th}, 75^{th}) annual cost of IDSR activities In this equation, a negative result indicates net cost savings, when the cost savings of IDSR (i.e., cost of treatments avoided due to cases averted) outweigh the costs of IDSR activities (surveillance and response).
We also determined the net cost per capita of IDSR as follow:
In this equation, the per capita IDSR costs were calculated using data from the whole country
Regardless of IDSR activities, any measured alteration in the epidemiology of meningitis, including any reduction in cases, could have been due to naturally occurring disease cycles. To remove any unknown effect of disease cycles or specific years, we individually compared health outcomes (incidence of cases, mortality, sequelae, and timetopeak of outbreak) between each outbreak before IDSR and each outbreak that occurred after IDSR implementation. This analysis removes the element of time sequence, and we only compare outcomes beforeversusafter the
start of IDSR. Specifically, we used the following general formula:
Using this formula, we generated 9,030 paired comparisons (105 outbreaks before IDSR x 86 outbreaks after IDSR) in outcomes for each of the following variables: incidence of cases, mortality, sequelae, and timetopeak of outbreak. We also examined the influence of 1996 data on these comparisons by rerunning the simulation excluding all outbreaks that occurred in 1996 (giving 7,052 paired comparisons).
We then plotted the distribution of the differences between the paired comparisons (with and without the 1996 data) for the time to peak, and incidence of cases and mortality. We also calculated the median, 25^{th} and 75^{th} percentiles for the cases, deaths and sequelae averted (with and without the 1996 data). Similarly, we calculated the simple average, minimum and maximum of the differences in these health outcomes. Finally, we used the data from the paired comparisons to calculate costeffectiveness ratios as described earlier.
Based on our definition of outbreaks (10 per 100,000 – see earlier), we identified 105 outbreaks before adoption of IDSR and 86 after adoption of IDSR (
Note: District level weekly new meningitis cases from Burkina Faso for the years 1996–2007 were obtained from the WHO MultiDiseases Surveillance Center in Ouagadougou, Burkina Faso. Incidence recorded in a particular district experiencing a meningitis outbreak  the incidence data do not apply to the entire country. For list of districts reporting outbreaks recorded in this Figure, see
The median and the 25^{th} and 75^{th} percentiles of the weekly number of meningitis cases and deaths before and after IDSR implementation are presented in
Note: Data source: WHO MultiDiseases Surveillance Center, Ouagadougou, Burkina Faso. For each weekly incidence rate, we calculated the median, 25^{th} and 75^{th} percentile of the 105 and 82 outbreaks before IDSR and 86 outbreaks after IDSR. Before IDSR, the median (25^{th} and 75^{th} percentile) cumulative number of meningitis cases per outbreak was 185.0 (139.5 and 377.0) per 100,000 inhabitants when 1996 data were included and was 167.9 (135.3 and 281.0) per 100,000 inhabitants when 1996 data were excluded. After IDSR, the median (25^{th} and 75^{th} percentile) cumulative number of deaths per outbreak was 142.0 (100.3 and 248.2) per 100,000 inhabitants.
Data source: WHO MultiDiseases Surveillance Center, Ouagadougou, Burkina Faso. For each weekly mortality rate, we calculated the median, 25^{th} and 75^{th} percentile of the 105 and 82 outbreaks before IDSR and 86 outbreaks after IDSR. Before IDSR, the median (25^{th} and 75^{th} percentile) cumulative number of deaths per outbreak was 23.8 (17.9 and 35.9) per 100,000 inhabitants when 1996 data were included and was 20.5 (16.1 and 30.3) per 100,000 inhabitants when 1996 data were excluded. After IDSR, the median (25^{th} and 75^{th} percentile) cumulative number of deaths per outbreak was 12.6 (8.8 and 21.3) per 100,000 inhabitants.
The pattern of differences in peaks is also seen when comparing cumulative cases. After IDSR implementation, the average and median (50^{th} percentile) incidences per outbreak dropped by 135 per 100,000 and 40 per 100,000 (pvalue 0.0001,
Including 1996 data  Excluding 1996 data  
Outcome measures  Before  After  Difference  pvalue  Before  After  Difference  pvalue  
(n = 105)  (n = 86)  (n = 82)  (n = 86)  
Total cumulative cases (per 100,000)  
Mean  346  211  −135  0.0267  228  211  −17  0.034  
25th percentile  140  100  −40  135  100  −35  
50th percentile  185  142  −43  168  142  −26  
75th percentile  377  248  −129  281  248  −33  
Total cumulative deaths (per 100,000)  
Mean  35  16  −19  <0.0001  26  16  −10  <0.0001  
25th percentile  18  9  −9  16  9  −7  
50th percentile  23  13  −10  21  13  −8  
75th percentile  36  21  −15  30  21  −9  
Timetopeak of outbreak  
Mean  6  4  −2  <0.0001  6  4  −2  <0.0001  
25th percentile  4  3  −1  3  3  0  
50th percentile  6  4  −2  6  4  −2  
75th percentile  9  5  −4  8  5  −3  
Time to reach % total cases  
25% of cases  10.5  10.2  −0.3  0.1578  10.4  10.2  −0.2  0.2954  
50% of cases  12.6  12  −0.7  0.0123  12.5  12  −0.5  0.1081  
75% of cases  14.4  13.6  −0.7  0.015  14.1  13.6  −0.5  0.0404  
Time to reach % total deaths  
25% of deaths  9.9  9  −0.9  0.0052  9.6  9  −0.6  0.0361  
50% of deaths  12.2  11.6  −0.6  0.0193  11.9  11.6  −0.3  0.1313  
75% of deaths  14  13.6  −0.4  0.0609  13.7  13.6  −0.1  0.4307 
These represented the 25^{th} percentile, 50^{th} percentile, and 75^{th} percentile of the total number of cases and deaths and the time to peak before and after IDSR.
Time to peak of outbreak represented the time elapsed from reaching the alert threshold of a weekly incidence of 5 cases per 100,000 inhabitants to the week with the maximum weekly incidence.
Time to reach total cases and deaths represented the time interval between the first week of each calendar year and the week during the outbreak period when the total cases and deaths were reached.
These are the average time for outbreaks to reach the 25th, 50th, and 75^{th} percent of total cases and deaths. For example, before IDSR it took 10.5 weeks during an outbreak to reach 25% of all cases attributed to that outbreak.
We did not find any evidence of a statistically significant correlation associated between doses of vaccine imported and outbreaks (
The median net cost of averting a case of meningitis was $23 per meningitis case averted (25^{th} percentile: $30; 75^{th} percentile: cost savings), and the median cost per death and sequelae averted were $98 and $126, respectively (
Including 1996 data Median  Excluding 1996 data Median  
(  (  
Total cost of IDSR  3,684  3,684 
Activities (per 100,000)  
Treatment costs  2,675  1,609 
Avoided (per 100,000)  (  ( 
Net IDSR costs  1,009  2,075 
(per 100,000)  (  ( 
Cost per case  23  80 
Averted  (  ( 
Cost per death  98  263 
Averted  (  ( 
Cost per sequelae  126  669 
Averted  (  ( 
Cost per capita  0.01  0.02 
(  ( 
See reference 26. No vaccine cost included because no evidence found of incremental importation of vaccine doses correlated with implementation of IDSR (see
We estimated the treatment costsaving by multiplying the mean medical cost ($62.25) per meningitis patient by the difference in the number of cases per outbreak that occurred before IDSR versus after IDSR.
We calculated the number of sequelae by assuming 20% of all meningitis illnessrelated survivors have neurological defects.
In more than 50% of the pairings in the paired outbreak analysis, which removes the influence of time and disease cycles, the outbreaks after IDSR implementation had lower incidence of cases and mortality, as well as shorter timetopeak (
Note: Comparison of data of each of the 105 outbreaks before IDSR with each of the 86 outbreaks after IDSR. Removing 1996 data reduces total outbreaks before IDSR to 82. Effects on outcomes correlated with IDSR are represented on the horizontal axes: negative numbers indicated reducing effects and positive numbers indicated increasing effects on timetopeak of outbreak (Panel A), number of cases per outbreak (Panel B), and number of deaths per outbreak (Panel C).
Outcomes measures  Including 1996 data  Excluding 1996 data  
Median  Average^{¶}
 Median  Average^{¶}
 



 
Total cumulative cases averted (per 100,000)  −48  −134  −27  −17 
Total cumulative deaths averted (per 100,000)  −10  −19  −8  −10 
Total cumulative sequelae averted (per 100,000)  −15  −44  −8  −6 
We compared health outcomes for each of the 105 outbreaks before IDSR with each of the 86 outbreaks after IDSR implementation. We then reran these paired comparisons excluding the 1996, before IDSR data.
Number of health outcomes averted was calculated using the following equation:
Negative figure indicates reduction in cases, deaths, and sequelae per outbreak after IDSR implementation.
Including 1996 data  Excluding 1996 data  
Median  Median  

 
Total cost of IDSR  3,684  3,684 
Activities (per 100,000)  
Treatment costs  2,982  1,662 
Avoided (per 100,000) 
 (− 
Net IDSR costs  568  2,022 
(per 100,000) 


Cost per case  15  76 
Averted 


Cost per death  68  270 
Averted 


Cost per sequelae  46  239 
Averted 


Cost per capita  0.01  0.02 


We calculated the median, 25^{th} and 75^{th} percentile costeffectiveness based on the difference of the generated health outcomes (after IDSR versus before IDSR) distribution.
We estimated the treatment costs avoided by multiplying the mean medical cost ($62.25) per meningitis patient by the number of cases averted.
The IDSR strategy is focused on improving the collection and analysis of infectious disease surveillance data to more rapidly and accurately detect, and respond to, disease outbreaks. This should hopefully reduce the overall burden of disease
We could not find any statistically significant evidence of an increase in vaccine imports. We can only speculate that the reduced incidence of cases and deaths are due to IDSR allowing public health officials to better target existing resources to outbreaks. That is, the IDSR system enables public health officials to identify and get to an outbreak sooner, and be more certain which villages and areas need interventions.
The study's main limitation is the uncertainty in assuming that the reductions in cases were due to IDSR. We do not have enough evidence to claim the degree that the differences that we measured were due to IDSR. As mentioned earlier, the nature of a public health system such as IDSR prevents us from designing and conducting a controlled scientific experiment. It is possible that the changes in epidemiology that we recorded were due to changes in other factors, such as a change in the circulating serogroups and strains of
Other limitations include the fact that our retrospective survey may not have fully captured all data. This would be due to the limitations of public data records (e.g., no vaccine distribution and use records at country level) or “readily” accessible program records of specific public health projects (such as meningitis specific vaccine program) that run parallel to the national public health system. Further, we assumed that the accuracy of recording cases and deaths due to meningitis remained unchanged during the period studied. The implementation of IDSR could have improved accuracy, potentially increasing the estimated impact of IDSR. However, it is impossible to assess the degree, and therefore impact, of any changes in accuracy over time.
We believe, even with the study limitations, that these results indicate that IDSR is likely to be a costeffective public health system. A completely accurate accounting of its benefits to society, such as money and lives saved has yet to be documented. It is also clear, however, that IDSR is not a complete solution to eliminating the burden of meningococcal meningitis. Given the difficulty of measuring the impact of surveillance and response systems, it may well be that policymakers will have to make assessments of the value of IDSR and similar systems using the type of data we presented here.
List of IDSR priority diseases and diseases of public health importance weekly or monthly reported in Burkina Faso during the study period.
(0.02 MB DOC)
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Health outcomes and duration of meningococcal meningitis outbreak in selected districts before (19962002) and after (2003–2007) IDSR implementation in Burkina Faso.
(0.28 MB DOC)
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Pattern of annual vaccines imported into Burkina Faso before (1996–2002) and after (2003–2008) IDSR implementation.
(0.04 MB DOC)
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Pattern of annual vaccines delivered to region before (1996–2002) and after (2003–2008) IDSR implementation.
(0.04 MB DOC)
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Annual costs (in 2002 US $) of all public healthrelated surveillance and IDSRrelated activities per category of resources and health structure level in Burkina Faso: 2002 to 2005.
(0.07 MB DOC)
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Cost of treating a meningitisrelated illness at regional hospital and district health facility levels in Burkina Faso during the 2002 epidemic season.
(0.03 MB DOC)
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Results of statistical analyses of doses of vaccine imported into Burkina Faso from 1996 to 2008: Impact of IDSR on amounts of vaccine imported.
(0.03 MB DOC)
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Pathogens identified by PCR, Latex, and Culture of CSF and serum samples in countries under enhanced surveillance (IDSR) of meningitis in the WHO African region.
(0.17 MB DOC)
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The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the CDC, the World Health Organization Africa region (WHOAFRO), and the Ministry of Health of Burkina Faso.
We thank our colleagues on the integrated disease surveillance and response teams at the WHO Regional Office for Africa, the WHO headquarters, and the Centers for Disease Control and Prevention for their comments during the development and implementation of the study. We wish to acknowledge, specifically, William Perea and Alejandro Javier Costa (WHOHQ) and Montse SorianoGabarro (GlaxoSmithKline Biologicals) for providing important vaccine data for this study. We also thank Dr. Jay Wenger, DPEI/NCEZID/CDC, for detailed comments on earlier versions of this manuscript.