Meningococcal disease and season in sub-Saharan Africa

In silico Characterization of a Hypothetical Protein (PBJ89160.1) from Neisseria meningitidis Exhibits a New Insight on Nutritional Virulence and Molecular Docking to Uncover a Therapeutic Target

Objective

Neisseria meningitidis is an encapsulated, diplococcus, kidney bean-shaped bacteria that causes bacterial meningitis. Our study hopes to advance our understanding of disease progression, the spread frequency of the bacteria in people, and the interactions between the bacteria and human body by identifying a functional protein, potentially serving as a target for meningococcal medicine in the future.

Methods

A hypothetical protein HP (PBJ89160.1) from N. meningitidis was employed in this study for extensive structural and functional characterization. In the predictive functional role of HP, several constitutive bioinformatics approaches are applied, such as prediction of physiological properties, domain and motif family function, secondary and tertiary structure prediction, energy minimization, quality validation, docking, and ADMET analysis. To create the protein's three-dimensional (3D) structure, a template protein (PDB_ID: 3GXA) is used with 99% sequence identity by homology modeling technique with the HHpred server. To mitigate the pathogenicity associated with the HP function, it was docked with the natural ligand methionine and five other drug compounds like Verapamil, Loperamide, Thioridazine, Chlorpromazine, and Auranofine.

Results

The protein is predicted to be acidic, soluble and hydrophilic by physicochemical properties analysis. Subcellular localization analysis demonstrated the protein to be periplasmic. The HP has an ATP-binding cassette transporter (also known as ABC transporter) involved in uptake of methionine (MetQ) that creates nutritional virulence in host. Energy minimization, multiple quality assessments, and validation value determination led to the conclusion that the HP model had a workable and acceptable quality. Following ADMET analysis and binding affinity assessments from the docking studies, Loperamide emerged as the most promising therapeutic compound, effectively inhibiting the ATP transporter activity of the HP.

Conclusion

Comparative genomic analysis revealed that this protein is specific to N. meningitidis and has no homologs in human proteins, thereby identifying it as a potential target for therapeutic intervention.

Trends in Neisseria meningitidis serogroups amongst patients with suspected cerebrospinal meningitis in the meningitis belt of Ghana: a 5-year retrospective study

BACKGROUND

Serogroup A Neisseria meningitidis was the major cause of meningococcal meningitis epidemics in the African meningitis belt before 2010 when the monovalent meningococcal A conjugate vaccine (MenAfriVac) was introduced in the region. Therefore, this study aimed to establish the trends in N. meningitidis serogroups from 2016 to 2020 in Ghana's meningitis belt.

METHODS

Polymerase chain reaction (PCR) confirmed laboratory results of suspected cases of cerebrospinal meningitis from January, 2016 to March, 2020 were obtained from the Tamale Public Health Laboratory. The data were subjected to trend analysis using Statistical Package for the Social Sciences version 25. Differences between discrete variables were analyzed using the Cochran-Armitage trend test.

RESULTS

Of the 2,426 suspected cases, 395 (16.3%) were confirmed positive for N. meningitidis using PCR. Serogroup X showed a significant upward trend (P < 0.01), and serogroup W showed a downward trend (P < 0.01). However, no significant trend was observed for any other serogroup.

CONCLUSION

This study showed the emergence of serogroup X, a non-vaccine type, as the predominant N. meningitidis serogroup in the wake of a declining serogroup W in Ghana's meningitis belt.

Association between temperature variability and global meningitis incidence

BACKGROUND

Meningitis can cause devastating epidemics and is susceptible to climate change. It is unclear how temperature variability, an indicator of climate change, is associated with meningitis incidence.

METHODS

We used global meningitis incidence data along with meteorological and demographic data over 1990-2019 to identify the association between temperature variability and meningitis. We also employed future (2020-2100) climate data to predict meningitis incidence under different emission levels (SSPs: Shared Socioeconomic Pathways).

RESULTS

We found that the mean temperature variability increased by almost 3 folds in the past 30 years. The largest changes occurred in Australasia, Tropical Latin America, and Central Sub-Saharan Africa. With a logarithmic unit increase in temperature variability, the overall global meningitis risk increases by 4.8 %. Australasia, Central Sub-Saharan Africa, and High-income North America are the most at-risk regions. Higher statistical differences were identified in males, children, and the elderly population. Compared to high-emission (SSP585) scenario, we predicted a median reduction of 85.8 % in meningitis incidence globally under the low-emission (SSP126) climate change scenario by 2100.

CONCLUSION

Our study provides evidence for temperature variability being in association with meningitis incidence, which suggests that global actions are urgently needed to address climate change and to prevent meningitis occurrence.

Infectious Diseases Associated with Desert Dust Outbreaks: A Systematic Review

Background: Desert dust outbreaks and dust storms are the major source of particulate matter globally and pose a major threat to human health. We investigated the microorganisms transported with desert dust particles and evaluated their potential impact on human health. Methods: A systematic review of all reports on the association between non-anthropogenic desert dust pollution, dust microorganisms and human health is conducted. Results: In total, 51 articles were included in this review. The affected regions studied were Asia (32/51, 62.7%) followed by Europe (9/51, 17.6%), America (6/51, 11.8%), Africa (4/51, 7.8%) and Australia (1/51, 2.0%). The Sahara Desert was the most frequent source of dust, followed by Asian and American deserts. In 39/51 studies the dust-related microbiome was analyzed, while, in 12/51 reports, the association of desert dust with infectious disease outbreaks was examined. Pathogenic and opportunistic agents were isolated from dust in 24/39 (61.5%) and 29/39 (74.4%) of the studies, respectively. A significant association of dust events with infectious disease outbreaks was found in 10/12 (83.3%) reports. The infectious diseases that were mostly investigated with dust outbreaks were pneumonia, respiratory tract infections, COVID-19, pulmonary tuberculosis and coccidioidomycosis. Conclusions: Desert dust outbreaks are vehicles of a significant number of pathogenic or opportunistic microorganisms and limited data indicate an association between dust events and infectious disease outbreaks. Further research is required to strengthen the correlation between dust events and infectious diseases and subsequently guide preventive public health measures.

Efficacy and Effectiveness of the Meningococcal Conjugate Group A Vaccine MenAfriVac® in Preventing Recurrent Meningitis Epidemics in Sub-Saharan Africa

For more than a century, epidemic meningococcal disease mainly caused by serogroup A Neisseria meningitidis has been an important public health problem in sub-Saharan Africa. To address this problem, an affordable meningococcal serogroup A conjugate vaccine, MenAfriVac®, was developed specifically for populations in the African meningitis belt countries. MenAfriVac® was licensed based on safety and immunogenicity data for a population aged 1-29 years. In particular, the surrogate markers of clinical efficacy were considered to be the higher immunogenicity and the ability to prime immunological memory in infants and young children compared to a polysaccharide vaccine. Because of the magnitude of serogroup A meningitis epidemics and the high morbidity and mortality burden, the World Health Organization (WHO) recommended the MenAfriVac® deployment strategy, starting with mass vaccination campaigns for 1-29-year-olds to rapidly interrupt serogroup A person-to-person transmission and establish herd protection, followed by routine immunization of infants and toddlers to sustain protection and prevent epidemics. After licensure and WHO prequalification of MenAfriVac®, campaigns began in December 2010 in Burkina Faso, Mali, and Niger. By the middle of 2011, it was clear that the vaccine was highly effective in preventing serogroup A carriage and disease. Post introduction meningitis surveillance revealed that serogroup A meningococcal disease had disappeared from all age groups, suggesting that robust herd immunity had been achieved.

Optimal control and cost-effective analysis of the 2017 meningitis outbreak in Nigeria

This paper presents a deterministic model for Neisseria meningitidis, a bacterium that causes meningitis. The model was parameterized using data from the 2017 meningitis outbreak in Nigeria. Optimal control theory was applied to investigate the optimal strategy for curtailing the spread of the disease using control variables determined from sensitivity analysis. These control variables are personal-protection such as the use of facial masks, and vaccination. The results show that the two controls avert more infections at low costs. Furthermore, a reciprocal relationship exists between the use of facial masks and vaccine. That is, when the use of facial masks is high, the use of vaccine is low and vice versa. Cost-effective analysis was applied to investigate the most cost-effective strategy from various combination of control strategies. The results show that strategy combining all the control variables is the most cost-effective strategy followed by the strategy involving both personal-protection, the vaccination-only strategy was the least cost-effective. Although vaccination strategy is not cost-effective in this study, it is as effective in curtailing the infection as the other two control strategies. The study suggests that governments of communities with limited resources should consider complementing the use of vaccine with the use of facial mask particularly in hard-to-reach places in their communities.

Compartmental models for seasonal hyperendemic bacterial meningitis in the African meningitis belt

The pathophysiological mechanisms underlying the seasonal dynamic and epidemic occurrence of bacterial meningitis in the African meningitis belt remain unknown. Regular seasonality (seasonal hyperendemicity) is observed for both meningococcal and pneumococcal meningitis and understanding this is critical for better prevention and modelling. The two principal hypotheses for hyperendemicity during the dry season imply (1) an increased risk of invasive disease given asymptomatic carriage of meningococci and pneumococci; or (2) an increased transmission of these bacteria from carriers and ill individuals. In this study, we formulated three compartmental deterministic models of seasonal hyperendemicity, featuring one (model1-'inv' or model2-'transm'), or a combination (model3-'inv-transm') of the two hypotheses. We parameterised the models based on current knowledge on meningococcal and pneumococcal biology and pathophysiology. We compared the three models' performance in reproducing weekly incidences of suspected cases of acute bacterial meningitis reported by health centres in Burkina Faso during 2004-2010, through the meningitis surveillance system. The three models performed well (coefficient of determination R2, 0.72, 0.86 and 0.87, respectively). Model2-'transm' and model3-'inv-transm' better captured the amplitude of the seasonal incidence. However, model2-'transm' required a higher constant invasion rate for a similar average baseline transmission rate. The results suggest that a combination of seasonal changes of the risk of invasive disease and carriage transmission is involved in the hyperendemic seasonality of bacterial meningitis in the African meningitis belt. Consequently, both interventions reducing the risk of nasopharyngeal invasion and the bacteria transmission, especially during the dry season are believed to be needed to limit the recurrent seasonality of bacterial meningitis in the meningitis belt.

Meningococcal carriage within households in the African meningitis belt: A longitudinal pilot study

OBJECTIVES

Carriers of Neisseria meningitidis are a key source of transmission. In the African meningitis belt, where risk of meningococcal disease is highest, a greater understanding of meningococcal carriage dynamics is needed.

METHODS

We randomly selected an age-stratified sample of 400 residents from 116 households in Bamako, Mali, and collected pharyngeal swabs in May 2010. A month later, we enrolled all 202 residents of 20 of these households (6 with known carriers) and collected swabs monthly for 6 months prior to MenAfriVac vaccine introduction and returned 10 months later to collect swabs monthly for 3 months. We used standard bacteriological methods to identify N. meningitidis carriers and fit hidden Markov models to assess acquisition and clearance overall and by sex and age.

RESULTS

During the cross-sectional study 5.0% of individuals (20/400) were carriers. During the longitudinal study, 73 carriage events were identified from 1422 swabs analyzed, and 16.3% of individuals (33/202) were identified as carriers at least once. The majority of isolates were non-groupable; no serogroup A carriers were identified.

CONCLUSIONS

Our results suggest that the duration of carriage with any N. meningitidis averages 2.9 months and that males and children acquire and lose carriage more frequently in an urban setting in Mali. Our study informed the design of a larger study implemented in seven countries of the African meningitis belt.

Comparison of Models Analyzing a Small Number of Observed Meningitis Cases in Navrongo, Ghana

The "meningitis belt" is a region in sub-Saharan Africa where annual outbreaks of meningitis occur, with epidemics observed cyclically. While we know that meningitis is heavily dependent on seasonal trends, the exact pathways for contracting the disease are not fully understood and warrant further investigation. Most previous approaches have used large sample inference to assess impacts of weather on meningitis rates. However, in the case of rare events, the validity of such assumptions is uncertain. This work examines the meningitis trends in the context of rare events, with the specific objective of quantifying the underlying seasonal patterns in meningitis rates. We compare three main classes of models: the Poisson generalized linear model, the Poisson generalized additive model, and a Bayesian hazard model extended to accommodate count data and a changing at-risk population. We compare the accuracy and robustness of the models through the bias, RMSE, and standard deviation of the estimators, and also provide a detailed case study of meningitis patterns for data collected in Navrongo, Ghana.

Airborne dust and high temperatures are risk factors for invasive bacterial disease

Background

The Sahel region of West Africa has the highest bacterial meningitis attack and case fatality rate in the world. The effect of climatic factors on patterns of invasive respiratory bacterial disease is not well documented.

Objective

We aimed to assess the link between climatic factors and occurrence of invasive respiratory bacterial disease in a Sahel region of Niger.

Methods

We conducted daily disease surveillance and climatic monitoring over an 8-year period between January 1, 2003, and December 31, 2010, in Niamey, Niger, to determine risk factors for bacterial meningitis and invasive bacterial disease. We investigated the mechanistic effects of these factors on Streptococcus pneumoniae infection in mice.

Results

High temperatures and low visibility (resulting from high concentrations of airborne dust) were identified as significant risk factors for bacterial meningitis. Dust inhalation or exposure to high temperatures promoted progression of stable asymptomatic pneumococcal nasopharyngeal carriage to pneumonia and invasive disease. Dust exposure significantly reduced phagocyte-mediated bacterial killing, and exposure to high temperatures increased release of the key pneumococcal toxin pneumolysin through increased bacterial autolysis.

Conclusion

Our findings show that climatic factors can have a substantial influence on infectious disease patterns, altering density of pneumococcal nasopharyngeal carriage, reducing phagocytic killing, and resulting in increased inflammation and tissue damage and consequent invasiveness. Climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of invasive bacterial disease in regions of the world exposed to high temperatures and increased airborne dust.

Meningococcal serogroup W135 in the African meningitis belt: epidemiology, immunity and vaccines

In the sub-Saharan African meningitis belt there is a region of hyperendemic and epidemic meningitis stretching from Senegal to Ethiopia. The public health approaches to meningitis epidemics, including those related to vaccine use, have assumed that Neisseria meningitidis serogroup A will cause the most disease. During 2001 and 2002, the first large-scale epidemics of serogroup W135 meningitis in sub-Saharan Africa were reported from Burkina Faso. The occurrence of N. meningitidis W135 epidemics has led to a host of new issues, including the need for improved laboratory diagnostics for identifying serogroups during epidemics, an affordable supply of serogroup W135-containing polysaccharide vaccine for epidemic control where needed, and re-evaluating the long-term strategy of developing a monovalent A conjugate vaccine for the region. This review summarizes the existing data on N. meningitidis W135 epidemiology, immunology and vaccines as they relate to meningitis in sub-Saharan Africa.

Global epidemiology of invasive meningococcal disease

Neisseria meningitidis is one of the leading causes of bacterial meningitis globally and can also cause sepsis, pneumonia, and other manifestations. In countries with high endemic rates, the disease burden places an immense strain on the public health system. The worldwide epidemiology of invasive meningococcal disease (IMD) varies markedly by region and over time. This review summarizes the burden of IMD in different countries and identifies the highest-incidence countries where routine preventive programs against Neisseria meningitidis would be most beneficial in providing protection. Available epidemiological data from the past 20 years in World Health Organization and European Centre for Disease Prevention and Control collections and published articles are included in this review, as well as direct communications with leading experts in the field. Countries were grouped into high-, moderate-, and low-incidence countries. The majority of countries in the high-incidence group are found in the African meningitis belt; many moderate-incidence countries are found in the European and African regions, and Australia, while low-incidence countries include many from Europe and the Americas. Priority countries for vaccine intervention are high- and moderate-incidence countries where vaccine-preventable serogroups predominate. Epidemiological data on burden of IMD are needed in countries where this is not known, particularly in South- East Asia and Eastern Mediterranean regions, so evidence-based decisions about the use of meningococcal vaccines can be made.

Knowledge, attitudes, and practices related to meningitis in northern Ghana

Meningitis has a significant impact in the Sahel, but the mechanisms for transmission and factors determining a person's vulnerability are not well understood. Our survey examined the knowledge, attitudes, and practices of people in a meningitis-endemic area in the Upper East region of northern Ghana to identify social, economic, and behavioral factors that may contribute to disease transmission and possible interventions that might improve health outcomes. Key results suggest potential interventions in response to the risk posed by migration, especially seasonal migration, a lack of knowledge about early symptoms causing delayed treatment, and a need for further education about the protective benefits of vaccination.

The Role of Weather in Meningitis Outbreaks in Navrongo, Ghana: A Generalized Additive Modeling Approach

Bacterial (meningococcal) meningitis is a devastating infectious disease with outbreaks occurring annually during the dry season in locations within the 'Meningitis Belt', a region in sub-Saharan Africa stretching from Ethiopia to Senegal. Meningococcal meningitis occurs from December to May in the Sahel with large epidemics every 5-10 years and attack rates of up to 1000 infections per 100,000 people. High temperatures coupled with low humidity may favor the conversion of carriage to disease as the meningococcal bacteria in the nose and throat are better able to cross the mucosal membranes into the blood stream. Similarly, respiratory diseases such as influenza and pneumonia might weaken the immune defenses and add to the mucosa damage. Although the transmission dynamics are poorly understood, outbreaks regularly end with the onset of the rainy season and may begin anew with the following dry season. In this paper, we employ a generalized additive modeling approach to assess the association between number of reported meningitis cases and a set of weather variables (relative humidity, rain, wind, sunshine, maximum and minimum temperature). The association is adjusted for air quality (dust, carbon monoxide), as well as varying degrees of unobserved time-varying confounding processes that co-vary with both the disease incidence and weather. We present the analysis of monthly reported meningitis counts in Navrongo, Ghana, from 1998-2008.

Opa proteins and CEACAMs: pathways of immune engagement for pathogenic Neisseria

Neisseria meningitidis and Neisseria gonorrhoeae are globally important pathogens, which in part owe their success to their ability to successfully evade human immune responses over long periods. The phase-variable opacity-associated (Opa) adhesin proteins are a major surface component of these organisms, and are responsible for bacterial adherence and entry into host cells and interactions with the immune system. Most immune interactions are mediated via binding to members of the carcinoembryonic antigen cell adhesion molecule (CEACAM) family. These Opa variants are able to bind to different receptors of the CEACAM family on epithelial cells, neutrophils, and T and B lymphocytes, influencing the innate and adaptive immune responses. Increased epithelial cell adhesion creates the potential for prolonged infection, invasion and dissemination. Furthermore, Opa proteins may inhibit T-lymphocyte activation and proliferation, B-cell antibody production, and innate inflammatory responses by infected epithelia, in addition to conferring increased resistance to antibody-dependent, complement-mediated killing. While vaccines containing Opa proteins could induce adhesion-blocking and bactericidal antibodies, the consequence of CEACAM binding by a candidate Opa-containing vaccine requires further investigation. This review summarizes current knowledge of the immunological consequences of the interaction between meningococcal and gonococcal Opa proteins and human CEACAMs, considering the implications for pathogenesis and vaccine development.

Avoiding hypothermia, an intervention to prevent morbidity and mortality from pneumonia in young children

Observations and experiments in animals and human beings grant plausibility to the hypothesis that hypothermia is a risk factor for pneumonia. Exposure of body to cold stress causes alterations in the systemic and local defenses against respiratory infections, favoring the infection by inhalation of pathogens normally present in the oropharynx. Neonates and young infants with hypothermia have an increased risk of death; however, there is no strong demonstration that hypothermia leads to pneumonia in these children. Studies that properly addressed the problem of confounding variables have shown an association between cold weather and pneumonia incidence. Probably the strongest evidence that supports the plausibility of the hypothesis is provided by the controlled comparison between patients with traumatic brain injury treated with hypothermia and those treated under normal body temperature. The association between exposure to cold and pneumonia is strong enough to warrant further research focused in young children in developing countries.

Using satellite images of environmental changes to predict infectious disease outbreaks

A strong global satellite imaging system is essential for predicting outbreaks.

Recent events clearly illustrate a continued vulnerability of large populations to infectious diseases, which is related to our changing human-constructed and natural environments. A single person with multidrug-resistant tuberculosis in 2007 provided a wake-up call to the United States and global public health infrastructure, as the health professionals and the public realized that today’s ease of airline travel can potentially expose hundreds of persons to an untreatable disease associated with an infectious agent. Ease of travel, population increase, population displacement, pollution, agricultural activity, changing socioeconomic structures, and international conflicts worldwide have each contributed to infectious disease events. Today, however, nothing is larger in scale, has more potential for long-term effects, and is more uncertain than the effects of climate change on infectious disease outbreaks, epidemics, and pandemics. We discuss advances in our ability to predict these events and, in particular, the critical role that satellite imaging could play in mounting an effective response.

Using satellite images of environmental changes to predict infectious disease outbreaks

Recent events clearly illustrate a continued vulnerability of large populations to infectious diseases, which is related to our changing human-constructed and natural environments. A single person with multidrug-resistant tuberculosis in 2007 provided a wake-up call to the United States and global public health infrastructure, as the health professionals and the public realized that today's ease of airline travel can potentially expose hundreds of persons to an untreatable disease associated with an infectious agent. Ease of travel, population increase, population displacement, pollution, agricultural activity, changing socioeconomic structures, and international conflicts worldwide have each contributed to infectious disease events. Today, however, nothing is larger in scale, has more potential for long-term effects, and is more uncertain than the effects of climate change on infectious disease outbreaks, epidemics, and pandemics. We discuss advances in our ability to predict these events and, in particular, the critical role that satellite imaging could play in mounting an effective response.

Relationships between climate and year-to-year variability in meningitis outbreaks: a case study in Burkina Faso and Niger

Background

Every year, West Africa is afflicted with Meningococcal Meningitis (MCM) disease outbreaks. Although the seasonal and spatial patterns of disease cases have been shown to be linked to climate, the mechanisms responsible for these patterns are still not well identified.

Results

A statistical analysis of annual incidence of MCM and climatic variables has been performed to highlight the relationships between climate and MCM for two highly afflicted countries: Niger and Burkina Faso. We found that disease resurgence in Niger and in Burkina Faso is likely to be partly controlled by the winter climate through enhanced Harmattan winds. Statistical models based only on climate indexes work well in Niger showing that 25% of the disease variance from year-to-year in this country can be explained by the winter climate but fail to represent accurately the disease dynamics in Burkina Faso.

Conclusion

This study is an exploratory attempt to predict meningitis incidence by using only climate information. Although it points out significant statistical results it also stresses the difficulty of relating climate to interannual variability in meningitis outbreaks.

The descriptive epidemiology of Streptococcus pneumoniae and Haemophilus influenzae nasopharyngeal carriage in children and adults in Kilifi district, Kenya

BACKGROUND

Transmission and nasopharyngeal colonization are necessary steps en route to invasive pneumococcal or Haemophilus influenzae disease but their patterns vary geographically. In East Africa we do not know how these pathogens are transmitted between population subgroups nor which serotypes circulate commonly.

METHODS

We did 2 cross-sectional nasopharyngeal swab surveys selecting subjects randomly from a population register to estimate prevalence and risk-factors for carriage in 2004. H. influenzae type b vaccine was introduced in 2001.

RESULTS

Of 450 individuals sampled in the dry season, 414 were resampled during the rainy season. Among subjects 0-4, 5-9, and 10-85 years old pneumococcal carriage prevalence was 57%, 41%, and 6.4%, respectively. H. influenzae prevalence was 26%, 24%, and 3.0%, respectively. Prevalence of H. influenzae type b in children <5 years was 1.7%. Significant risk factors for pneumococcal carriage were rainy season (odds ratio [OR]: 1.65), coryza (OR: 2.29), and coculture of noncapsulate H. influenzae (OR: 7.46). Coryza was also a risk factor for H. influenzae carriage (OR: 1.90). Of 128 H. influenzae isolates, 113 were noncapsulate. Among 279 isolates of Streptococcus pneumoniae, 40 serotypes were represented and the distribution of serotypes varied significantly with age; 7-valent vaccine-types, vaccine-related types, and nonvaccine types comprised 47%, 19%, and 34% of strains from children aged <5 years. Among older persons they comprised 25%, 28%, and 47%, respectively (P = 0.005).

CONCLUSIONS

The study shows that pneumococcal carriage is common up to 9 years of age and that the majority of serotypes carried at all ages are not covered specifically by the 7-valent pneumococcal conjugate vaccine.

Climate change and infectious diseases

The worldwide upturn in the occurrence of both new (emerging) and reemerging or spreading infectious diseases highlights the importance of underlying environmental and social conditions as determinants of the generation, spread, and impact of infectious diseases in human populations. Human ecology is undergoing rapid transition. This encompasses urbanization, rising consumerism, changes in working conditions, population aging, marked increases in mobility, changes in culture and behavior, evolving health-care technologies, and other factors. Global climate change is becoming a further, and major, large-scale influence on the pattern of infectious disease transmission. It is likely to become increasingly important over at least the next halfcentury, as the massive, highinertial, and somewhat unpredictable process of climate change continues. The many ways in which climate change does and will influence infectious diseases are subject to a plethora of modifying influences by other factors and processes: constitutional characteristics of hosts, vectors and pathogens; the prevailing ambient conditions; and coexistent changes in other social, economic, behavioral, and environmental factors. This global anthropogenic process, climate change, along with other unprecedented global environmental changes, is beginning to destabilize and weaken the planet's life-support systems. Infectious diseases, unlike other diseases, depend on the biology and behavior—each often climate-sensitive—of two or more parties. Hence, these diseases will be particularly susceptible to changes as the world's climate and its climate-sensitive geochemical and ecological systems undergo change over the coming decades.

Comparative study of meningitis dynamics across nine African countries: a global perspective

Background

Meningococcal meningitis (MM) represents an important public health problem especially in the "meningitis belt" in Africa. Although seasonality of epidemics is well known with outbreaks usually starting in the dry season, pluri-annual cycles are still less understood and even studied. In this context, we aimed at study MM cases time series across 9 sahelo-sudanian countries to detect pluri-annual periodicity and determine or not synchrony between dynamics. This global and comparative approach allows a better understanding of MM evolution in time and space in the long-term.

Results

We used the most adapted mathematical tool to time series analyses, the wavelet method. We showed that, despite a strong consensus on the existence of a global pluri-annual cycle of MM epidemics, it is not the case. Indeed, even if a clear cycle is detected in all countries, these cycles are not as permanent and regular as generally admitted since many years. Moreover, no global synchrony was detected although many countries seemed correlated.

Conclusion

These results of the first large-scale study of MM dynamics highlight the strong interest and the necessity of a global survey of MM in order to be able to predict and prevent large epidemics by adapted vaccination strategy. International cooperation in Public Health and cross-disciplines studies are highly recommended to hope controlling this infectious disease.

Prospects for vaccine prevention of meningococcal infection

Neisseria meningitidis is the leading cause of bacterial meningitis in the United States and worldwide. A serogroup A/C/W-135/Y polysaccharide meningococcal vaccine has been licensed in the United States since 1981 but has not been used universally outside of the military. On 14 January 2005, a polysaccharide conjugate vaccine that covers meningococcal serogroups A, C, W-135, and Y was licensed in the United States for 11- to 55-year-olds and is now recommended for the routine immunization of adolescents and other high-risk groups. This review covers the changing epidemiology of meningococcal disease in the United States, issues related to vaccine prevention, and recommendations on the use of the new vaccine.

Meningococcal conjugate vaccines

Disease caused by Neisseria meningitidis is associated with high mortality rates and significant sequelae. Polysaccharide meningococcal vaccines have been available for > 20 years, and have been used in travellers to control outbreaks, and in some countries for adolescents entering college, although they provide only a short duration of immunity and do not produce a herd effect. Monovalent and quadrivalent (A, C, Y, W-135) meningococcal conjugate vaccines have recently been licensed and endorsed for use in infants, children, adolescents and adults in various countries. Among the key features of the new meningococcal conjugate vaccines are stimulation of both B cell-dependent and T cell-dependent immune responses, induction of immunological memory and booster effects, longer-term protection, reduction of nasopharyngeal carriage of N. meningitidis, and herd immunity. Large, randomised, double-blind studies in adults, adolescents, children and infants have demonstrated the immunogenicity and safety of the new meningococcal conjugate vaccine formulations.

Naturally-acquired immunity to Neisseria meningitidis group A

Group A meningococcal disease is epidemic in Sudan, less common in Uganda, a country bordering the "meningitis belt," and rare in North America. The basis of naturally-acquired group A immunity is unknown but in North America protection has been attributed to a high prevalence of serum anticapsular antibodies elicited by cross-reacting bacteria. We measured group A anticapsular antibody concentrations and bactericidal titers in sera from 236 adults (47 from the Sudan obtained at the height of a group A epidemic, 57 from Uganda, and 132 from North America). Anticapsular antibody concentrations were higher in Sudanese sera than in North American or Ugandan sera (geometric mean of 31.5 versus 5.4 and 5.3 microg/ml, respectively, P < 0.0001). Bactericidal titers of > or =1:4 (presumed to be a protective titer when measured with human complement) were detected in 66% of Sudanese sera as compared with 27 and 23%, respectively, of North American and Ugandan sera (P < 0.0001). Bactericidal activity was inhibited by group A polysaccharide in 58% of the Sudanese bactericidal sera as compared to 17 and 6% of North America and Ugandan bactericidal sera (P < 0.0005). Approximately 50% of non-bactericidal Sudanese sera had high IgA anticapsular antibody concentrations, which were rare in bactericidal Sudanese sera. Thus, serum anticapsular antibodies and bactericidal activity are prevalent in Sudanese exposed to a group A epidemic. Cross-reacting group A anticapsular antibodies are prevalent in North American and Ugandan sera, but bactericidal activity is infrequent and when present is largely directed at non-capsular antigens.

Review of the cost effectiveness of immunisation strategies for the control of epidemic meningococcal meningitis

Outbreaks of meningococcal disease have caused devastation worldwide. Effective vaccines have not been used routinely, due to perceived limitations of the duration of effectiveness as well as immunogenicity when administered during infancy. Given the sporadic nature of outbreaks, the optimal use of these vaccines to control both short-term epidemic and endemic meningococcal disease has been the subject of much debate. Seven economic studies on the use of polysaccharide vaccination strategies help to highlight the relevant epidemiological and economic issues surrounding the decisions for their use. Five of these studies were based in Africa, the region where annual incidence rates can be several orders of magnitude greater than the rest of the world. These studies demonstrated that vaccination against meningococcal disease during outbreak situations is suboptimal given the inability to rapidly immunise populations in a timely fashion in resource-poor areas. However, depending on the disease incidence and the ability to deliver vaccines, the polysaccharide vaccine can be cost effective for preventive strategies when given prior to the start of outbreaks, either through presumptive vaccination or through a modified routine delivery strategy. Economic analyses of mass immunisation campaigns and modelled routine vaccination suggest that routine use of meningococcal vaccines for preventive strategies could be within the range of cost-effective public health interventions in those regions of the world where meningococcal disease is endemic. This includes the meningococcal belt of Africa, the Sahelian region.

Environmental risk and meningitis epidemics in Africa

Epidemics of meningococcal meningitis 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.

Meningococcal immunology

There is a major need for an effective vaccine against serogroup B disease. The long-term efficacy of the serogroups A, C, Y and W135 conjugate vaccines and the need for booster vaccines has to be determined, as does the effect of changing epidemiology in the United States and worldwide. Control of serogroup A disease in sub-Saharan Africa is a major challenge.

Pathogenesis, Therapy, and Prevention of Meningococcal Sepsis

Neisseria meningitidis (meningococcus), an exclusive pathogen of humans, is the cause of sepsis (meningococcemia) and meningitis, often in otherwise healthy individuals. Several hundred thousand cases of meningococcal disease occur worldwide each year, a number that is frequently accentuated by epidemic outbreaks. In recent years, significant advances, fueled by new molecular approaches and genome sequencing projects, have improved our understanding of the pathogenesis of meningococcal disease and have led to progress in the development of the next generation of meningococcal vaccines. However, the mortality of meningococcal disease remains 10% to 15% for all cases, and is up to 40% in patients with severe sepsis. This review summarizes current knowledge of the pathogenesis, therapy, and prevention of meningococcal disease with emphasis on meningococcal sepsis.

Meningococcal disease and meteorological conditions in Auckland, New Zealand

OBJECTIVE

The purpose of the study was to explore and model the relationship between meteorological variables and meningococcal disease notifications in Auckland during an ongoing group B meningococcal disease epidemic.

METHODS

An ecological study design was used to investigate the relationship between 1,097 notified cases of meningococcal disease from January 1992 to December 1998 among residents of Auckland's three health districts and various meteorological variables. Descriptive epidemiology and Poisson regression modelling were used to describe this relationship.

FINDINGS

The study found that the occurrence of meningococcal disease varied with season, increased with high humidity and cooler temperatures and appeared to decline with prolonged periods of heavy rain. Poisson regression analysis showed a significant relationship between the expected number of cases developing meningococcal disease on a given day and season and temperature.

DISCUSSION

The results of the modelling analysis provide the initial work for the future development of a predictive tool to forecast the magnitude and duration of the annual peak in meningococcal disease incidence using routine notification data and meteorological recordings, thus allowing for better management of the public health workload and interventions, and the appropriate timing of media campaigns.

Where is the meningitis belt? Defining an area at risk of epidemic meningitis in Africa

Mapping an area at risk of epidemics of meningococcal meningitis in Africa has significant implications for their prevention and case treatment, through the targeted development of improved surveillance systems and control policies. Such an area was described using information obtained from published and unpublished reports of meningitis epidemics between 1980 and 1999 and cases of meningococcal disease reported by surveillance systems to WHO. The Sahel bore the greatest epidemic burden, with over two-thirds of documented outbreaks and high attack rates. In addition to those already in the Meningitis Belt, countries affected included Guinea-Bissau, Guinea, Côte d'Ivoire, Togo, the Central African Republic and Eritrea. Elsewhere epidemics were reported from a band of countries around the Rift Valley and Great Lakes regions extending as far south as Mozambique and from here west to Angola and Namibia in southern Africa. The cumulative pan-continental analysis provided evidence of an epidemic-susceptible area which extends beyond the region accepted as the Meningitis Belt and which, moreover, may be partially determined by the physical environment, as shown by a striking correspondence to the 300-1100-mm mean annual rainfall isohyets.

Timely detection of meningococcal meningitis epidemics in Africa

BACKGROUND

Epidemics of meningococcal disease in Africa are commonly detected too late to prevent many cases. We assessed weekly meningitis incidence as a tool to detect epidemics in time to implement mass vaccination.

METHODS

Meningitis incidence for 41 subdistricts in Mali was determined from cases recorded in health centres (1989-98) and from surveillance data (1996-98). For incidence thresholds of 5 to 20 cases per 100000 inhabitants per week, we calculated sensitivity and specificity for detecting epidemics, and determined the time lapse between threshold and epidemic peak.

FINDINGS

We recorded 9084 meningitis cases. Clinic-based weekly incidence of 5 and 10 cases per 100000 inhabitants detected all meningitis epidemics (sensitivity 100%, 95% CI 93-100), with median threshold-to-peak time of 5 and 3 weeks. Under-reporting reduced sensitivity: only surveillance thresholds of 5 or 7 cases per 100000 inhabitants per week detected all epidemics. Crossing the lower threshold before the 10th calendar week doubled epidemic risk relative to crossing it later (relative risk 2.1, 95% CI 1.4-3.2). At 10 cases per 100000 inhabitants per week, specificity for outbreak prediction was 88%, 95% CI 83-91). For populations under 30000, 3 to 5 cases in one or two weeks predicted epidemics with 85% to 97% specificity.

INTERPRETATION

Low meningitis thresholds improve timely detection of epidemics. Ten cases per 100000 inhabitants per week in one area confirm epidemic activity in a region, with few false alarms. An alert threshold of 5 cases per 100000 inhabitants per week allows time to investigate, prepare for an epidemic, and initiate mass vaccination where appropriate. For populations under 30000, the alert threshold is two cases in a week. High quality surveillance is essential.

Seasonal variation in host susceptibility and cycles of certain infectious diseases

Seasonal cycles of infectious diseases have been variously attributed to changes in atmospheric conditions, the prevalence or virulence of the pathogen, or the behavior of the host. Some observations about seasonality are difficult to reconcile with these explanations. These include the simultaneous appearance of outbreaks across widespread geographic regions of the same latitude; the detection of pathogens in the off-season without epidemic spread; and the consistency of seasonal changes, despite wide variations in weather and human behavior. In contrast, an increase in susceptibility of the host population, perhaps linked to the annual light/dark cycle and mediated by the pattern of melatonin secretion, might account for many heretofore unexplained features of infectious disease seasonality. Ample evidence indicates that photoperiod-driven physiologic changes are typical in mammalian species, including some in humans. If such physiologic changes underlie human resistance to infectious diseases for large portions of the year and the changes can be identified and modified, the therapeutic and preventive implications may be considerable.

Epidemiology and pathogenesis of Neisseria meningitidis

Neisseria meningitidis, an exclusive pathogen of humans, remains the leading worldwide cause of meningitis and fatal sepsis, usually in otherwise healthy individuals. In recent years, significant advances have improved our understanding of the epidemiology and genetic basis of meningococcal disease and led to progress in the development of the next generation of meningococcal vaccines. This review summarizes current knowledge of the human susceptibility to and the epidemiology and molecular pathogenesis of meningococcal disease.

Evaluation of meningococcal meningitis vaccination strategies for the meningitis belt in Africa

BACKGROUND

Although the meningococcal polysaccharide vaccine has contributed to the control of Group A meningitis in the "meningitis belt" of Africa, recurrent large outbreaks have led to questions regarding vaccination strategy. We evaluated current and hypothetical vaccination strategies for the region.

METHODS

A model was formulated to analyze the effectiveness and costs of vaccine campaigns in response to outbreaks based on 7 years of weekly incidence data from Burkina Faso. Additional models analyzed the potential impact and costs of either a 1- or 4-dose routine scheduled delivery of meningococcal polysaccharide vaccine based on data reported to the World Health Organization from 16 countries during 1948 through 1996. Vaccine efficacy, vaccination coverage and economic data from literature reviews provided model assumptions.

RESULTS

For Burkina Faso neither 1- nor 4-dose vaccination schedules would prevent >30% of meningitis cases compared with the 42% prevented through an outbreak response program of vaccinating districts, which reach an incidence of 15 per 100000 persons for 2 weeks. For the entire meningitis belt, routine coverage with the 1- or 4-dose schedule meningococcal vaccine would require 4.9 and 19.6 million doses annually, respectively, for an annual net cost of $4.4 to $12.3 million and prevent an average 10300 to 12600 cases (23 to 28%), assuming a long term vaccine efficacy of 50%. In addition an initial "catch-up" campaign costing up to $72 million to vaccinate the population from 1 to 30 years of age would be required before achieving that level of effectiveness.

CONCLUSION

Given the relatively poor routine vaccination coverage in this region, current strategies of vaccination campaigns that achieve higher coverage would generally be more effective and less costly than the modeled routine scheduled programs, assuming that campaigns can be rapidly implemented. Until a better vaccine is available, countries in this region would be more efficient in improving the response times to outbreaks, perhaps through improved surveillance, and in bolstering existing vaccination infrastructures rather than embarking on strategies of questionable effectiveness.

Weather conditions and cerebrospinal meningitis in Benin (Gulf of Guinea, West Africa)

Over a 28-year period cerebrospinal meningitis, in sporadic as well as epidemic situations, mainly affected the Beninese territory from November to March, April or sometimes May. On the average, the acme occurred in February-March. A regression analysis confirmed that 14 to 34.5% of the temporal variability of the disease was due to the northern trade wind (harmattan) and a low absolute humidity in the northern areas, which constitute the main epidemiological pole of the country. On the contrary, cerebrospinal meningitis and climate turned out to be fully independent one from the other in the southernmost areas, where the harmattan is seldom experienced although the meningitis belt is at the present time spreading southwards. But the case-fatality ratio was especially high in the coastal region and during the off season, i.e. when endemic meningitis predominantly affected small children aged under one year. In any way, the climate-meningitis relationship proved to be weaker than is sometimes assumed, perhaps because this relationship is partly overshadowed by both anthropic effects (vaccination campaigns) and latency before disease outbreak.

Pyogenic meningitis in children in north-western Ethiopia

A 5-year retrospective study of all children with acute pyogenic meningitis admitted to a district hospital in north-western Ethiopia was carried out from 1990 to 1994. A total of 132 cases of pyogenic meningitis were identified. The causative bacteria were identified in 85 (64%) patients. The most common pathogen was Haemophilus influenzae (40%) with a case fatality rate of 29.4%, followed by Neisseria meningitidis (36.4%), which had a case fatality rate of 16.1%, and Streptococcus pneumoniae (20%) with a case fatality rate of 35.3%. Boys accounted for 64% of the patients, giving a male:female ratio of 1.7:1. Median patient age was 0.75 years, and median ages of those infected by H. influenzae, N. meningitidis, and S. pneumoniae were 0.5, 4.0 and 0.6 years, respectively. The overall case fatality rate was 28%. The mortality rate of children below the age of 1 year was 38.4% and 13.8% for those above 1 year.

Meningococcal meningitis and carriage in western Zaire: a hypoendemic zone related to climate?

An analysis of bacteria recovered from cerebrospinal fluid over a 16-year period at a rural hospital in western Zaire showed that Neisseria meningitidis accounted for only five (2.2%) isolates. A survey of naso-pharyngeal colonisation with N. meningitidis in 378 healthy children was undertaken to distinguish whether this low frequency was due to lack of carriage or, by inference, lack of the co-factors necessary to permit invasive disease. N. meningitidis was recovered from only three (0.78%) of the children. All isolates were non-typable strains of low pathogenicity. A review of studies examining the aetiology of bacterial meningitis and the geographical location of epidemics of meningococcal meningitis in and around Zaire reveals a 'hypoendemic zone', the limits of which correlate well with the area in which mean absolute humidity remains above 10 g m-3 of air throughout the year. Continuous high absolute humidity appears to reduce the transmission of meningococci.

Pattern and antibiotic susceptibility of bacteria in pyogenic meningitis in a children's emergency room population in Maiduguri, Nigeria, 1988-1992

From January 1988 to November 1992, 107 (3.5%) of 3074 postneonatal children admitted to the Children's Emergency Room, University of Maiduguri Teaching Hospital, Nigeria, had sporadic pyogenic meningitis; 66 (61.7%) were aged < or = 12 months. Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae together were responsible for 77.3% (58) of 75 culture-proven cases, 13.4% (10) had Enterobacteriaceae, 5.3% (4) had Staphylococcus aureus and 4% (3) untyped alpha-haemolytic streptococci. Fifty percent of 62 bacteria were resistant to ampicillin, 47.2% of 36 to penicillin and 10.7% of 56 to chloramphenicol; none of 21 bacteria was simultaneously resistant to all three antibiotics. Up until 1992, we have encountered treatment failure with a regimen containing chloramphenicol in only 2 of 53 patients; the 2 patients had coliform meningitis. Non-meningococcal bacteria are an important cause of sporadic pyogenic meningitis in sub-Saharan Nigeria and chloramphenicol is the most appropriate initial drug of choice at the present time for the management of sporadic meningitis.

Different seroprevalences of antibodies against Neisseria meningitidis serogroup A and Haemophilus influenzae type b in Sudanese and Swedish children

Sampling of sera from 202 Sudanese and 124 Swedish children 1-14 years of age was conducted at the end of the 1980s presenting an opportunity to compare the seroprevalence of anti-Neisseria meningitidis (MC) serogroup A antibodies in an area immediately before outbreak of an epidemic (Sudan 1988) with a low endemic area (Sweden). An ELISA antibody assay was developed for detection of antibodies against capsular polysaccharide of MC serogroup A and Haemophilus influenzae type b (Hib). Serum antibody against MC serogroup A was found significantly more frequently in Sudanese than in Swedish children. This indicates that factors other than herd immunity, as measured by serum antibodies against MC serogroup A polysaccharide, are important for avoidance of an MC serogroup A epidemic. The seroprevalence of Hib antibodies was, in contrast, significantly higher in Swedish than in Sudanese children, especially for 5-9-year-old children. A possible explanation may be the different systems of day-care of children in the two countries.

Clonal and antigenic analysis of serogroup A Neisseria meningitidis with particular reference to epidemiological features of epidemic meningitis in the People's Republic of China

Representative strains of serogroup A Neisseria meningitidis were chosen from all major meningitis epidemics worldwide since 1960 and subjected to analysis for the electrophoretic variation of 15 cytoplasmic allozymes and four outer membrane proteins. The 290 strains defined 84 unique electrophoretic types which were classified in nine subgroups. Tests with monoclonal antibodies specific for conserved pilin epitopes showed that the class I, IIa, and IIb epitopes were uniform within the subgroups. Similarly, the subgroups were uniform for expression of different variable regions of class 1 outer membrane protein, with a few minor exceptions. Many of the bacteria tested were isolated in the People's Republic of China, and the epidemiology of Chinese epidemics of meningococcal meningitis is described. The analysis approaches a global description of epidemic meningitis caused by serogroup A meningococci in the past 30 years.