Environmental risk and meningitis epidemics in Africa.Epidemics of meningococcal meningitis meningococcal meningitis n. An acute infectious disease affecting children and young adults characterized by inflammation of the meninges of the brain and spinal cord, headache, vomiting, convulsions, stiff neck, light sensitivity, and purpuric occur in areas with particular environmental characteristics. We present evidence that the relationship between the environment and the location of these epidemics is quantifiable and propose a model based on environmental variables to identify regions at risk for meningitis epidemics. These findings, which have substantial implications for directing surveillance activities and health policy, provide a basis for monitoring the impact of climate variability and environmental change on epidemic occurrence in Africa. ********** Epidemics of meningitis occur worldwide. However, the "meningitis belt meningitis belt A popular term for a region of sub-Saharan Africa where epidemics of group A meningococcal infection occur in cycles of ± 10 yrs " of Africa's Sahel region Sahel is one of Burkina Faso's 13 administrative regions. It was created on 2 July 2001 and had a population of 837,420 in 2002. The region's capital is Dori. Four provinces make up the region - Oudalan, Séno, Soum, and Yagha. has the greatest incidence of the disease, with large epidemics attributed to predominantly group A meningococci; the endemic levels found in this region would be considered epidemic elsewhere. Although factors predisposing populations to meningitis epidemics are poorly understood, population susceptibility, introduction of new strains, poor living conditions living conditions npl → condiciones fpl de vida living conditions npl → conditions fpl de vie living conditions living , and concurrent infections have all been implicated im·pli·cate tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates 1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot. 2. . Epidemics occur throughout Africa in the dry season, coincide with periods of very low humidity and dusty conditions, and disappear with the onset of the rains, suggesting that these environmental factors may also play an important role in the occurrence of the disease (1-3). Lapeyssonnie (4) observed in 1963 that epidemics largely occurred in a semi-arid zone south from the Sahara, with 300-1,100 mm mean annual rainfall, and Cheesbrough et al. (5) suggested in 1995 that areas that are humid throughout the year have low disease rates. In West Africa West Africa A region of western Africa between the Sahara Desert and the Gulf of Guinea. It was largely controlled by colonial powers until the 20th century. West African adj. & n. , Waddy wad·dy 1 Australian n. pl. wad·dies A heavy stick, especially a war club. tr.v. wad·died , wad·dy·ing, wad·dies To strike with a waddy. (1958) described an area that suffered epidemics as having "... only one definable frontier, the junction of the forest ... with the savanna savanna or savannah (both: səvăn`ə), tropical or subtropical grassland lying on the margin of the trade wind belts. ..., when there is an abrupt change from a permanently humid climate to one with a severe dry season" (6). Epidemics have been rarely reported from the humid forested or coastal regions, even when neighboring neigh·bor n. 1. One who lives near or next to another. 2. A person, place, or thing adjacent to or located near another. 3. A fellow human. 4. Used as a form of familiar address. v. areas are severely affected. The timing of future outbreaks is unpredictable; tools that identify the key environmental factors associated with areas prone to meningitis epidemics would help us to understand the basis for these outbreaks and eventually optimize prevention and control activities. We describe a model that predicts the probability, based on environmental information, of an area experiencing an epidemic of meningitis. Methods Epidemiologic Data Details of all known meningitis epidemics occurring before 2000 in countries comprising continental Africa were compiled from information documented in the published literature and unpublished institutional reports at the end of June 2001. All epidemics reported in the medical literature were identified in PubMed's online database of medical literature (United States National Library of Medicine Noun 1. United States National Library of Medicine - the world's largest medical library National Library of Medicine, U.S. National Library of Medicine , available from: URL URL in full Uniform Resource Locator Address of a resource on the Internet. The resource can be any type of file stored on a server, such as a Web page, a text file, a graphics file, or an application program. : http://www.ncbi.nlm.nih.gov/PubMed/) through manual searches and by cross-referencing publications. We obtained unpublished information from Web searches or directly from international and national organizations involved in disease control and humanitarian aid Humanitarian aid is material or logistical assistance provided for humanitarian purposes, typically in response to humanitarian crises. The primary objective of humanitarian aid is to save lives, alleviate suffering, and maintain human dignity. (1). Epidemics reported at the provincial (second administrative level) and district level were located by using administrative boundaries available from the U.S. Geological Survey The term geological survey can be used to describe both the conduct of a survey for geological purposes and an institution holding geological information. A geological survey EROS Eros, in Greek religion and mythology Eros (ēr`ŏs, ĕr`–), in Greek religion and mythology, god of love. He was the personification of love in all its manifestations, including physical passion at its strongest, tender, Data Centre Africa Data Dissemination Service, Sioux Falls Sioux Falls, city (1990 pop. 100,814), seat of Minnehaha co., SE S.Dak., on the Big Sioux River; settled 1856, inc. as a village 1877, as a city 1883. Settlers abandoned the site in 1862 because of Native American raids, but with the establishment (1865) of Fort , SD (available from: URL: http://edcintl.cr.usgs.gov/adds/). Locations of villages or towns were verified by using the National Imagery and Mapping Agency's GEONet gazetteer gazetteer (găz'ĭtēr`), dictionary or encyclopedia listing alphabetically the names of places, political divisions, and physical features of the earth and giving some information about each. (available from: URL: http://www.nima.mil/), historical reference atlases and maps contained in the original reports, and were mapped to the current administrative boundaries by using ArcView 3.1 geographic information system geographic information system (GIS) Computerized system that relates and displays data collected from a geographic entity in the form of a map. The ability of GIS to overlay existing data with new information and display it in colour on a computer screen is used primarily to (GIS) (ESRI (Environmental Systems Research Institute, Inc., Redlands, CA, www.esri.com) The world's leading developer of geographic information systems (GIS) software, including programs that plot ZIP codes and addresses, demographic information and detailed, color-coded data. , Redlands, CA). We assumed that events reported at the provincial level affected all constituent districts and excluded epidemics reported only at the national level. Events affecting parts of any one country in one epidemic season were considered as one epidemic. We then classified the 3,281 districts of Africa as ever or never having experienced a documented epidemic of meningitis. In this analysis, no attempt was made to distinguish between epidemics of different scales. Environmental Data Environmental information for the African continent was obtained from a variety of sources. In this analysis, we restricted data to variables available in the public domain with digital grid-based uniform continental coverage, which we considered important. Variables included monthly means (long-term averages) of absolute humidity absolute humidity n. The weight of water vapor present per unit volume of a gas or a mixture of gases. (7), absorbing aerosols (dust) and rainfall, mad land-surface maps of land-cover type and population density (Table 1). All data grids were incorporated into the GIS. To collect the seasonal variation in climate while reducing the number of explanatory variables without loss of information, we reprocessed the monthly means of each variable to create a single surface comprising categories representing unique seasonal profiles. This reprocessing Reprocessing may refer to:
[FIGURE 1 OMITTED] For every district, a value was extracted in GIS representing those grid cells A grid cell is a type of neuron found in the entorhinal cortex (EC) that fires strongly when an animal is in specific locations in an environment. Grid cells were discovered in 2005 and it is hypothesized that a network of these cells constitute a mental map of the spatial of each profile surface contained within the district boundary. These values comprised the most common seasonal profile class for each variable (absolute humidity, dust, and rainfall), the most common land-cover type, and the geometric mean (mathematics) geometric mean - The Nth root of the product of N numbers. If each number in a list of numbers was replaced with their geometric mean, then multiplying them all together would still give the same result. population density. Analysis A logistic regression In statistics, logistic regression is a regression model for binomially distributed response/dependent variables. It is useful for modeling the probability of an event occurring as a function of other factors. analysis was used to identify associations between a district ever or never having experienced an epidemic and the environment by using SPSS A statistical package from SPSS, Inc., Chicago (www.spss.com) that runs on PCs, most mainframes and minis and is used extensively in marketing research. It provides over 50 statistical processes, including regression analysis, correlation and analysis of variance. 11.0 software (SPSS Inc., Chicago, IL). Explanatory variables were first investigated individually and then entered stepwise stepwise incremental; additional information is added at each step. stepwise multiple regression used when a large number of possible explanatory variables are available and there is difficulty interpreting the partial regression into a forward conditional multiple regression Multiple regression The estimated relationship between a dependent variable and more than one explanatory variable. analysis. Because of the need to reduce colinearity, we did not analyze environmental variables with similar geographic distributions together in the same model. The final model was based on the simplest approach and a combination of variables that best predicted the distribution of epidemics. This model was created with and without weighting for the inverse size of the district to assign less weight to larger districts, which may have been more prone to ecologic variation and therefore inadequately represented by a single value. The probability of each district ever having had an epidemic was predicted by using the model. These probabilities were grouped into risk categories and mapped, and the estimated total population was extracted in GIS derived from population density forecasts (U.S. Geological Survey, 1990). The sensitivity and specificity of the model were assessed by examining the agreement between predicted and observed epidemic experience by using a receiver-operator characteristics (ROC) curve to select the optimal probability cutoff values on which predictions are based (10). The dataset was then split at random into two parts containing approximately 60% and 40% of the 3,281 districts. The model was recreated with the 60% dataset, using the same variables as above and used to predict the risk for epidemics in the remaining 40% (the validation set validation set Decision-making A group of Pts with a clinical finding of interest–eg, chest pain, who are studied prospectively in order to verify facets of their disease that had been previously identified as possible predictors of outcome. See Derivation set. ). We repeated this process 10 times and compared the mean sensitivity and specificity of the validation set with the model derived from the entire dataset. Residuals resulting from the differences between the observed and predicted risks were also calculated and mapped to establish whether errors in the model were randomly distributed, thereby supporting the validity of the model throughout the continent. Results The earliest documented meningitis outbreak in Africa affected a French garrison in 1841 in Algiers (11), and [greater than or equal to] 425 epidemics were documented at the subnational level for the next 158 years. These epidemics affected at least 1,231 (38%) of the 3,281 continental districts. Supporting our earlier findings, epidemics were not evenly distributed across the continent, instead affecting mainly districts in the Sahel and south of this region and extending from northern Uganda and the eastern part of Democratic Republic of Congo, through the Great Lakes Great Lakes, group of five freshwater lakes, central North America, creating a natural border between the United States and Canada and forming the largest body of freshwater in the world, with a combined surface area of c.95,000 sq mi (246,050 sq km). and the Rift Valley rift valley, elongated depression, trough, or graben in the earth's crust, bounded on both sides by normal faults and occurring on the continents or under the oceans. regions to Malawi and northeastern Mozambique, and from northeastern Mozambique west and south to include other parts of southern Africa
[FIGURE 2 OMITTED] Absolute humidity, dust and rainfall profiles, land-cover type, and population densities were independently associated with the location of epidemics. However, we found that absolute humidity profile and land-cover type were the best predictors in the final multivariable model. Certain dust profiles and population density made only marginal difference to the performance of the model and were excluded to maintain simplicity. In addition, absolute humidity and rainfall profiles predicted similar risks in geographic locations in north and west Africa, but a model including the former performed better for the entire continent than one including rainfall; for this reason, we kept absolute humidity as a variable. Weighting for district size did not improve the performance of the model and was discarded. The model, which is based on the absolute humidity profile and land-cover type, is described in terms of its baseline characteristics baseline characteristic Medical practice An initial finding or value in a Pt, before any formal intervention , estimated coefficients, standard errors, and contribution of the variables in Table 2. The risk map for epidemic experience in Africa derived from this model is presented in Figure 2b. The most important factor associated with the distribution of epidemics was humidity. Areas without a marked distinction between wet and dry seasons were less likely to have had epidemics than those with contrasting seasons. The areas without distinction between wet and dry seasons include deserts and the humid parts of coastal and central Africa, much of which are forested, and the areas with contrasting seasons comprise the semiarid semiarid said of regions of the earth which have dry climates but not as dry as those of arid climates. savannah Savannah, city, United States Savannah, city (1990 pop. 137,560), seat of Chatham co., SE Ga., a port of entry on the Savannah River near its mouth; inc. 1789. and grasslands of the Sahel and east and southern Africa. Surface maps of Africa demonstrated a close correspondence between humidity and land-cover types in these regions. The model also showed that, having accounted for the effects of humidity, sparsely vegetated and barren regions, areas of woodland mosaic, and shrub land were less likely than other regions to have ever had an epidemic. The Sahel, which has a prolonged dry season with low humidity was identified as the area with the greatest risk (p>0.6). Peripheral regions along its southern borders, where the dry season is shorter and less extreme, carry a moderate risk (p>0.4). The peripheral region extends from southern Sudan Southern Sudan is a region of Sudan, comprising ten of that country's provinces. The Sudanese government agreed to give autonomy to the region in the Comprehensive Peace Agreement[1] and Ethiopia to the Great Lakes and Rift Valley regions and parts of southern Africa peripheral to desert areas. The ROC curve ROC curve acronym for receiver operating characteristic curve. A graphical method of assessing the characteristic of a diagnostic test. used to describe the performance of the model in terms of its sensitivity and specificity at various cutoffs, and its overall accuracy independent of a single probability cutoff is shown in Figure 3. The model can discriminate between districts that have experienced epidemics and those that have never been affected. When the values for randomly selected districts were entered into the model, the epidemic risk assigned was higher for districts with epidemics than for those without in 82% of the cases. The areas identified by the model coincide to a large extent with the areas observed to have experienced epidemics. By using a probability cutoff value of [greater than or equal to] 0.4 for predicting epidemic experience, the model had a sensitivity and specificity of 83% and 67%, respectively; these statistics were confirmed in the validation process (Table 3). The map of residual risk Residual risk Related: Unsystematic risk unaccounted for An inclusive term (not a casualty status) applicable to personnel whose person or remains are not recovered or otherwise accounted for following hostile action. Commonly used when referring to personnel who are killed in action and whose bodies are not recovered. by the model had a random distribution, as expected for a model that worked well across the continent (not shown). According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. the model, 7% of the population of Africa live in very high-risk areas, 17% in high, and 27% in moderate (based on 1990 estimates), corresponding to 44, 102, and 162 million people, respectively (Table 4). [FIGURE 3 OMITTED] Discussion This study represents a comprehensive and detailed description of the spatial distribution of meningitis epidemics at the district level in Africa and the first attempt to develop a spatial forecasting model for meningitis epidemics on the basis of the environmental characteristics of the continent considered a priori a priori In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience. to be related to the spatial distribution of epidemics. The data have limitations that need to be considered for the proper interpretation of the models. For example, census data for Africa have limited accuracy (12), variables derived through remote sensing Deriving digital models of an area on the earth. Using special cameras from airplanes or satellites, either the sun's reflections or the earth's temperature is turned into digital maps of the area. may only partially capture surface conditions, and data from meteorologic me·te·or·ol·o·gy n. The science that deals with the phenomena of the atmosphere, especially weather and weather conditions. [French météorologie, from Greek stations in Africa are often incomplete (13-15). The epidemiologic data span more than a century whereas the environmental and population data are relatively recent. In addition, some epidemics were likely never reported, and small outbreaks and those occurring in the 19th and early 20th centuries are likely to be disproportionately underrepresented un·der·rep·re·sent·ed adj. Insufficiently or inadequately represented: the underrepresented minority groups, ignored by the government. . Problems in defining epidemics exist as well, since most reports lack clear or internationally recognized criteria; we had to accept the perception of an increased incidence that prompted outbreak reports. Moreover, the aggregation of local level statistics to an often larger and somewhat arbitrary district level, discrepancies between where people become ill and the location of notifying health facilities, and changes to district boundaries over time may each have resulted in potential loss of specificity. Despite these limitations, major outbreaks were unlikely to have gone completely unreported, and the long-term cumulative distribution of events is likely not misrepresented on a pancontinental scale. While population densities in Africa have increased greatly during the last 150 years and substantial land-use change (particularly in West Africa) is known to have occurred, the model was still able to identify the meningitis belt and areas previously described at risk beyond the Sahel (2-5,16); reports of epidemics occurring since 1999 have coincided with this description (available from: URL: http://www.who.int/disease-outbreak-news/). The model also has its limitations. We are aware of those imposed on the analysis by spatial relationships in the data, which indicate that the importance of regression effects may be overstated o·ver·state tr.v. o·ver·stat·ed, o·ver·stat·ing, o·ver·states To state in exaggerated terms. See Synonyms at exaggerate. o (17). No perfect model exists, but one can be developed that is based on the simplest approach and combination of variables that can be used to distinguish between areas with high and low risk of epidemic experience. We were restricted by the limited availability When customers of the PSTN make telephone calls, they commonly make use of a telecommunications network called a switched-circuit network. In a switched-circuit network, devices known as switches are used to connect the caller to the callee. of suitable datasets and chose the simplest combination of variables that best predicted outcome. While this choice is likely to have oversimplified o·ver·sim·pli·fy v. o·ver·sim·pli·fied, o·ver·sim·pli·fy·ing, o·ver·sim·pli·fies v.tr. To simplify to the point of causing misrepresentation, misconception, or error. v.intr. the association between meningitis epidemics and the environment, the model has the advantage of using data that are available in the public domain and, being based on a simple combination of variables, are an important basis on which to develop research and future operational applications in resource-limited settings. The analysis indicates not only that absolute humidity profiles and land-cover types can be used to distinguish between areas with high and low risk of epidemics but also that population density and dust may also be implicated. The incidence of meningococcal disease has previously been correlated with dry and dusty conditions in tropical and temperate climates (18-21). Humidity and land cover were included in the final model for statistical reasons, but dust and population density still have an independent effect and may be important in determining epidemic occurrence (22). The potential role of dust in precipitating epidemics is particularly interesting since dustiness in the meningitis belt has increased dramatically since the Sahelian droughts of the 1970s and 1980s. However, how environmental variables interact is unclear and remains the subject of extensive climatologic research. Furthermore, we did not take into account the effect of other nonenvironmental factors likely to be related to epidemics, such as population movement, vaccination coverage, and recent epidemics in the area. A combination of conditions is likely to be necessary for an epidemic to occur, and these nonenvironmental variables are likely to have additional predictive potential and should be considered in further studies. Risk maps of vector-borne diseases vector-borne disease Infectious diseases Any infection, usually transmitted by insects–eg, ticks–eg, Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, Colorado tick fever; mosquitos–eg, California-or La Crosse, St Louis, Eastern, Western in Africa based on environmental data have received considerable attention in recent years and are tools with public health potential (10,15). The mechanisms by which environmental factors influence meningitis epidemics in Africa are unclear (3). Areas within the traditional meningitis belt and beyond, however, are environmentally susceptible to epidemics with potentially large populations at risk; markers such as absolute humidity and dust profiles, land-cover type, and population density are independent predictors of these areas, in addition, rainfall and dust are predictors in some, but not all regions, and the potential to develop region-specific models that could be more sensitive within given ecologic zones warrants further study. Our findings could facilitate the development of models to identify regions with increased vulnerability to epidemics in the future and provide a basis for monitoring the impact of climate variability and environmental change on epidemic occurrence in Africa.
Table 1. Characteristics of the environmental variables
Temporal Resolution of
Variable resolution Time period grid squares
Interpolated
meteorologic
station data (a)
Average daily
mean absolute
humidity Mean monthly 1961-1990 0.5[degrees] lat
x 0.5[degrees]
long (nominal
50 km)
Average daily
rainfall Mean monthly 1961-1990 0.5[degrees] lat
x 0.5[degrees]
long (nominal
50 km)
Remotely sensed satellite data (b)
Average daily
aerosol index
(dust) Mean monthly 1980-1999 1.0[degrees] lat
x 1.25[degrees]
long (nominal
100 km)
Digital maps
Land-cover
type (c) 1992-1993 1 x 1 km
Population
density (d) 1990 0.042[degrees]
lat x
0.042[degrees]
long (nominal 4
km)
(a) Mean monthly climate averages (1961-1990) for absolute
humidity and rainfall (the former derived from vapor pressure and
mean temperature [7]) were obtained from the Climate Research
Unit, University of East Anglia, UK (available from: URL:
http//ipcc-ddc.cru.uea.ac.uk/).
(b) Dust was obtained as monthly aerosol index coverages from
the U.S. National Aeronautics and Space Administration (NASA),
Goddard Space Flight Center, Maryland (available from URL:
http://www.gsfc.nasa.gov/), excluding the period May 1993 to
June 1996 for which data are not available.
(c) Land-cover type was obtained from the USGS NASA PATHFINDER
1km project (available from: URL: http://edcdaac.usgs.gov/
1KM/1kmhomepage.html/).
(d) U.S. Geologic Survey 1990 population density forecasts
(available from: URL: http;//grid2.cr.usgs.gov/globalpop/africa/).
Table 2. Baseline characteristics, estimated coefficients, and
standard errors for the model
Epidemic experience (n
districts) (a)
Variable Ever (%) Never
Absolute humidity profile (b)
Class 1 15 (3) 527
Class 2 9 (6) 153
Class 3 19 (8) 228
Class 4 43 (47) 48
Class 5 143 (61) 93
Class 6 0 (0) 2
Class 7 118 (47) 132
Class 8 40 (28) 102
Class 9 106 (48) 117
Class 10 46 (22) 161
Class 11 16 (29) 39
Class 12 1 (11) 8
Class 13 90 (48) 97
Class 14 44 (52) 40
Class 15 178 (74) 64
Class 16 7 (37) 12
Class 17 25 (54) 21
Class 18 181 (80) 46
Class 19 105 (56) 84
Class 20 46 (39) 73
Land-cover type
Savanna 646 (39) 1006
Dryland cropland/pasture 44 (39) 68
Irrigated cropland/pasture 0 (0) 9
Cropland/grassland mosaic 198 (53) 174
Cropland/woodland mosaic 4 (4) 105
Grassland 123 (67) 61
Shrubland 6 (34) 127
Urban 3 (43) 4
Broadleaf deciduous forest 44 (39) 68
Evergreen broadleaf forest 37 (13) 248
Water bodies 20 (38) 33
Forest wetland 0 (0) 24
Barren/sparsely vegetated 46 (28) 120
Variable removed (e) Log likelihood Change in -2
log likelihood
Absolute humidity profile -2045.937 877.963
Land-cover type -1642.564 71.217
Multivariable analysis
Variable [beta] SE
Absolute humidity profile (b)
Class 1 Reference
Class 2 0.59 0.44
Class 3 1.00 (c) 0.36
Class 4 3.48 (c) 0.35
Class 5 3.97 (c) 0.31
Class 6 -2.44 15.73
Class 7 3.29 (c) 0.30
Class 8 2.40 (c) 0.33
Class 9 3.31 (c) 0.31
Class 10 2.12 (c) 0.32
Class 11 3.34 (c) 0.43
Class 12 2.17 (d) 1.13
Class 13 3.30 (c) 0.32
Class 14 4.00 (c) 0.36
Class 15 4.46 (c) 0.32
Class 16 3.61 (c) 0.59
Class 17 3.99 (c) 0.43
Class 18 4.82 (c) 0.32
Class 19 3.60 (c) 0.31
Class 20 3.45 (c) 0.35
Land-cover type
Savanna Reference
Dryland cropland/pasture -0.38 0.23
Irrigated cropland/pasture -7.02 7.14
Cropland/grassland mosaic -0.07 0.14
Cropland/woodland mosaic -1.97 (c) 0.56
Grassland 0.36 0.19
Shrubland -0.52 (c) 0.19
Urban 0.32 0.85
Broadleaf deciduous forest 0.17 0.23
Evergreen broadleaf forest 0.07 0.24
Water bodies -0.07 0.33
Forest wetland -2.82 4.55
Barren/sparsely vegetated -1.07 (c) 0.24
Variable removed (e) df Significance of change
Absolute humidity profile 19 <0.001
Land-cover type 12 <0.001
(a) Excludes five districts for which environmental data were
unavailable (in Sinai, Egypt, and Pemba, Tanzania).
(b) See Figure 1 for description of profile classes.
(c) p value [less than or equal to] 0.01.
(d) p value [less than or equal to] 0.05.
(e) Model if term removed.
Table 3. Performance of the model for predicting epidemic experience
at the district level (a)
Epidemic experience Observed
Predicted Ever Never Total districts
Ever 1,022 682 1,704
Never 209 1,363 1,572
Total districts 1,231 2,045 3,276
Model Sensitivity % Specificity %
(95% CI) (95% CI)
Final (100%) 83 (81 to 85) 67 (65 to 69)
Mean validation (40%) 84 (80 to 87) 65 (62 to 69)
(n=1a)
Excludes live districts for which environmental data were unvailable
CI, confidence interval.
Table 4. Population residing in districts at risk for meningitis
epidemics in Africa
Risk No. of districts 1990 population
in millions (%)
Low 1,572 291 (49)
Moderate 971 162 (27)
High 482 102 (17)
Very high 251 44 (7)
Not known 5 1 (<1)
Total 3,281 600
Acknowledgments We thank Jay Herman for facilitating access to the aerosol data used in the analyses, Ian Hastings for statistical advice, and all persons and organizations that have contributed to the Meningitis Forecasting Project for their support and collaboration. Financial support was received from the Meningitis Research Foundation (UK), the U.S. National Oceanic and Atmospheric Administration Noun 1. National Oceanic and Atmospheric Administration - an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; provides weather reports and forecasts floods and hurricanes and Office of Global Programs, and Medecins Sans Frontieres. References (1.) Molesworth AM, Thomson MC, Connor SJ, Cresswell MC, Morse AP, Shears P, et al. Where is the meningitis belt? 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See meningococcal meningitis. as seen in the Anglo-Egyptian Sudan Anglo-Egyptian Sudan was the name of Sudan between 1899 and 1956, when it was a condominium of the United Kingdom and Egypt (which was then under British influence). History Anglo-Egyptian Sudan was located in northern Africa immediately south of Egypt. . J Trop Med Hyg 1916;19:101-27. (12.) Deichman U. A medium resolution population database for Africa. Database documentation and digital database. Santa Barbara Santa Barbara (săn'tə bär`brə, –bərə), city (1990 pop. 85,571), seat of Santa Barbara co., S Calif., on the Pacific Ocean; inc. 1850. (CA): National Center for Geographic Information and Analysis, University of California The University of California has a combined student body of more than 191,000 students, over 1,340,000 living alumni, and a combined systemwide and campus endowment of just over $7.3 billion (8th largest in the United States). ; 1994. (13.) Herman JR, Bhartia PK, Torres O, Hsu C, Seftor C, Celarier E. Global distribution of UV-absorbing aerosols from Nimbus 7/TOMS data. J Geophys Res 1997;102:16911-22. (14.) New M, Hulme M, Jones P. Representing twentieth-century space-time climate variability. Part 1: development of a 1961-90 mean monthly terrestrial climatology climatology Branch of atmospheric science concerned with describing climate and analyzing the causes and practical consequences of climatic differences and changes. Climatology treats the same atmospheric processes as meteorology, but it also seeks to identify slower-acting . J Clim 1999;12:829-56. (15.) Thomson MC, Connor SJ. Environmental information systems for the control of arthropod arthropod Any member of the largest phylum, Arthropoda, in the animal kingdom. Arthropoda consists of more than one million known invertebrate species in four subphyla: Uniramia (five classes, including insects), Chelicerata (three classes, including arachnids and horseshoe vectors of disease. Med Vet Entomol 2000;14:227-44. (16.) Mpairwe Y, Matovu HL. Cerebrospinal meningitis in east Africa 1911-1965. Trans R Soc Trop Med Hyg 1971;65:70-7. (17.) Diggle P, Moyeed R, Rawlingson B, Thomson M. Childhood malaria in the Gambia: a case study in model-based geostatistics. Appl Stat 2002;51:493-506. (18.) Molineaux L. Climate and meningococcal disease. [PhD Thesis]. Berkeley (CA): University of Berkeley; 1969. (19.) Waddy BB. Climate and respiratory infections, Lancet 1952;263:674-7. (20.) Greenwood BM, Blakebrough IS, Bradley AK, Wali S, Whittle HC. Meningococcal disease and season in sub-Saharan Africa. Lancet 1984;326:1339-42. (21.) Besancenot JP, Boko M, Oke PC. Weather conditions and cerebrospinal meningitis in Benin (Gulf of Guinea Noun 1. Gulf of Guinea - a gulf off the southwest coast of Africa Bioko - an island in the Gulf of Guinea that is part of Equatorial Guinea Atlantic, Atlantic Ocean - the 2nd largest ocean; separates North and South America on the west from Europe and Africa , West Africa). Eur J Epidemiol 1997;13:807-15. (22.) Molesworth AM, Cuevas LE, Morse AP, Herman JR, Thomson MC. Dust clouds and spread of infection. Lancet 2002;359:81-2. Anna M. Molesworth, * Luis E. Cuevas, * Stephen J. Connor, * Andrew P. Morse, ([dagger]) and Madeleine C. Thomson * * Liverpool School of Tropical Medicine The Liverpool School of Tropical Medicine (LSTM), England, was founded on 12 November 1898, by a donation from Sir Alfred Lewis Jones, a Liverpool Shipowner. The donation of £350 created the first school of its kind. , Liverpool, United Kingdom; and ([dagger]) University of Liverpool The University of Liverpool is a university in the city of Liverpool, England. History The University was established in 1881 as University College Liverpool, admitting its first students in 1882. , Liverpool, United Kingdom Ms. Molesworth is a senior scientist at the Health Protection Agency Communicable Disease communicable disease n. A disease that is transmitted through direct contact with an infected individual or indirectly through a vector. Also called contagious disease. Surveillance Centre, London, UK. She has a research background in epidemiology and public health. Her interests include the application of geographic information systems to infectious disease Infectious disease A pathological condition spread among biological species. Infectious diseases, although varied in their effects, are always associated with viruses, bacteria, fungi, protozoa, multicellular parasites and aberrant proteins known as prions. epidemiology. Address for correspondence: Madeleine C. Thomson, International Research Institute for Climate Prediction Climate prediction refers to :
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