A Bayesian network approach to the study of historical epidemiological databases: modelling meningitis outbreaks in the Niger.

OBJECTIVE: To develop a tool for evaluating the risk that an outbreak of meningitis will occur in a particular district of the Niger after outbreaks have been reported in other, specified districts of the country. METHODS: A Bayesian network was represented by a graph composed of 38 nodes (one for each district in the Niger) connected by arrows. In the graph, each node directly influenced each of the "child" nodes that lay at the ends of the arrows arising from that node, according to conditional probabilities. The probabilities between "influencing" and "influenced" districts were estimated by analysis of databases that held weekly records of meningitis outbreaks in the Niger between 1986 and 2005. For each week of interest, each district was given a Boolean-variable score of 1 (if meningitis incidence in the district reached an epidemic threshold in that week) or 0. FINDINGS: The Bayesian network approach provided important and original information, allowing the identification of the districts that influence meningitis risk in other districts (and the districts that are influenced by any particular district) and the evaluation of the level of influence between each pair of districts. CONCLUSION: Bayesian networks offer a promising approach to understanding the dynamics of epidemics, estimating the risk of outbreaks in particular areas and allowing control interventions to be targeted at high-risk areas.

Can sputum collection practices for tuberculosis improve laboratory diagnosis of pneumonic plague in developing countries?

Africa reports 90% of human plague cases yet no guidelines currently exist for the safe and accurate collection of sputum from patients with suspected pneumonic plague. Using existing tuberculosis guidelines as a model and in conjunction with epidemiological and clinical features of pneumonic plague, the authors describe the importance of formal guidelines to enhance sputum collection practices and improve safety in developing countries. A model for suggested guidelines is given.

Plague outbreak in the Libyan Arab Jamahiriya.

Plague is circulating regularly in localised areas worldwide, causing sporadic cases outside Africa and remains endemic or causes limited outbreaks in some African countries. Furthermore, some notable outbreaks have been reported in Asia in the last 20 years. A limited outbreak with five cases has recently been notified by the health authorities of the Libyan Arab Jamahiriya.

Risk factors for Nipah virus encephalitis in Bangladesh.

Nipah virus (NiV) is a paramyxovirus that causes severe encephalitis in humans. During January 2004, twelve patients with NiV encephalitis (NiVE) were identified in west-central Bangladesh. A case-control study was conducted to identify factors associated with NiV infection. NiVE patients from the outbreak were enrolled in a matched case-control study. Exact odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by using a matched analysis. Climbing trees (83% of cases vs. 51% of controls, OR 8.2, 95% CI 1.25-infinity) and contact with another NiVE patient (67% of cases vs. 9% of controls, OR 21.4, 95% CI 2.78-966.1) were associated with infection. We did not identify an increased risk for NiV infection among persons who had contact with a potential intermediate host. Although we cannot rule out person-to-person transmission, case-patients were likely infected from contact with fruit bats or their secretions.

Clinical presentation of nipah virus infection in Bangladesh.

BACKGROUND: In Bangladesh, 4 outbreaks of Nipah virus infection were identified during the period 2001-2004. METHODS: We characterized the clinical features of Nipah virus-infected individuals affected by these outbreaks. We classified patients as having confirmed cases of Nipah virus infection if they had antibodies reactive with Nipah virus antigen. Patients were considered to have probable cases of Nipah virus infection if they had symptoms consistent with Nipah virus infection during the same time and in the same community as patients with confirmed cases. RESULTS: We identified 92 patients with Nipah virus infection, 67 (73%) of whom died. Although all age groups were affected, 2 outbreaks principally affected young persons (median age, 12 years); 62% of the affected persons were male. Fever, altered mental status, headache, cough, respiratory difficulty, vomiting, and convulsions were the most common signs and symptoms; clinical and radiographic features of acute respiratory distress syndrome of Nipah illness were identified during the fourth outbreak. Among those who died, death occurred a median of 6 days (range, 2-36 days) after the onset of illness. Patients who died were more likely than survivors to have a temperature >37.8 degrees C, altered mental status, difficulty breathing, and abnormal plantar reflexes. Among patients with Nipah virus infection who had well-defined exposure to another patient infected with Nipah virus, the median incubation period was 9 days (range, 6-11 days). CONCLUSIONS: Nipah virus infection produced rapidly progressive severe illness affecting the central nervous and respiratory systems. Clinical characteristics of Nipah virus infection in Bangladesh, including a severe respiratory component, appear distinct from clinical characteristics reported during earlier outbreaks in other countries.

[From genomics to surveillance, prevention and control: new challenges for the African meningitis belt]. / Ceinture africaine de la méningite: de la génomique aux stratégies de surveillance, de lutte et de prévention.

An international conference was held in Niamey, Niger, in November 2005. It aimed at reviewing the current situation in the meningitis belt. This region stretches from Senegal to Ethiopia and is characterized by high levels of seasonal endemicity with large epidemics of meningococcal meningitis occurring cyclically, generally caused by N. meningiditis serogroup A. WHO currently recommends a reactive strategy based on rapid detection of epidemics, intervention with antibiotics to treat cases and mass vaccination with a meningococcal polysaccharide vaccine to halt the outbreak. Epidemiological patterns of the disease in Africa have been changing with the occurrence of outbreaks outside the meningitis belt and with the emergence of serogroup W135, which first caused an epidemic among Hajj pilgrims in 2000 and then a large-scale meningitis outbreak in Burkina Faso in 2002. Consequently enhanced laboratory surveillance and confirmation of the strain responsible for the outbreak are required. New rapid dipstick tests have been developed through a collaboration between Institut Pasteur and CERMES. They are designed for bedside diagnosis and detect meningococcal antigens present in CSF using immunochromatography. The treatment of meningococcal meningitis during epidemics is based on short-course, long-acting oily chloramphenicol. An alternative is the use of ceftriaxone, which is equally effective and can be used in pregnant women and infants. A low-cost, monovalent serogroup A meningococcal conjugate vaccine for large-scale use in Africa is under development. In spite of the emergence of W135 strains in the meningitis belt, N. meningiditis A continues to be the principal strain isolated during the epidemic seasons and elimination of outbreaks of N. meningiditis serogroup A can still be considered as the primary objective of a preventive vaccination strategy.

[Plague outbreaks in the Mediterranean area during the 2nd World War, epidemiology and treatments]. / Epidémiologie et prise en charge des épidémies de peste en Méditerranée au cours de la Seconde Guerre Mondiale.

Before the Second World War, the plague was still rife in North Africa but occurred only as sporadic cases or small outbreaks as in Egypt or Morocco. The permanent foci of infected wild rodent were the cause of these rural outbreaks. In 1943 and 1944, plague came back in several Mediterranean towns and ports and was considered as a serious danger for the Allied Forces. These resurgences were related to the World War as well as the overpopulation of the cities, regroupings and population movements, relaxation of prophylactic measures of the plague in sea transport. The Allied Forces medical officers then showed the resistance of Yersinia pestis to penicillin which they had been supplied with recently, the effectiveness of sulphamides but mortality remained high (27%). In parallel, the drastic fight against rodents and fleas (DDT) gave excellent results.

[First major epidemic caused by Neisseria meningitidis serogroup W135 in Africa?]. / Premiere epidemie de garnde amplier provoquee par Neisseria meningitidis W135 en Afrique?

Neisseria meningitidis serogroup W 135 (N.m. W 135) has caused sporadic infections and small epidemics such as those that occurred during religious pilgrimages in Saudi Arabia in 2000 and in 2001. It is routinely isolated from specimens coming from African countries. The first major epidemic involving N.m. W 135 occurred in Burkina Faso between January and May 1992. There were more than 1300 cases including 1500 deaths. Enhanced surveillance of circulating strains showed that N.m. W 135 accounted for 83% of the 203 positive cerebrospinal fluid specimen cultures. The offending organism was identical to the strain that caused the smaller epidemic in Saudi Arabia in 2000. Due to the shortage of tetravalent meningococcal vaccine against N.m. W 135, the Health Ministry based its response to the epidemic on treatment of symptomatic patients using chloramphenicol and ampicillian. These drugs were distributed free. The emergence of N.m. W135 has impacted public health in Africa. Repeated identification of this serogroup in Burkina Faso during 2002 raises the risk that similar outbreak will occur in the meningitis belt during the next epidemic season. The high cost of tetravalent meningococcal vaccine compounded with the only progressive increase in production capacity underline the need to reinforce surveillance of circulating strains and available treatment facilities. Control strategy for epidemic meningitis is currently the focus of close collaboration between the WHO and the health authorities and corresponding institutions in the countries involved.

[Democratic Republic of the Congo: between civil war and the Marburg virus. International Committee of Technical and Scientific Coordination of the Durba Epidemic]. / République Démocratique du Congo: entre guerre civile et virus Marburg. Comite International de Coordination Technique et Scientifique de l'Epidemie de Durba.

Because the epidemiology of viral hemorrhagic fever is unclear, each outbreak is a spectacular event that focuses the attention of the international scientific community. When an epidemic of Marburg virus disease occurred in the Durba region located in the northeastern part of the People's Republic of the Congo, 23 scientists were sent from 12 different countries. Sixty of the 73 people infected died. The first case was observed in December 1998 and the last in May 1999. Because of political unrest in the country, the outbreak was not reported immediately and most data was collected by observers retrospectively. However Marburg virus infection was confirmed in 5 of 16 patients in whom testing was performed and person-to-person transmission was demonstrated. Thus the Durba outbreak was the first epidemic of Marburg virus disease not involving laboratory contamination. Initial epidemiologic findings suggest that the first cases involved miners who were probably infected by contact with an animal reservoir such as bats. Further studies to determine seroprevalence in the general population and virologic testing on animals captured in the zone should provide answers to these questions.

Leptospirosis and Ebola virus infection in five gold-panning villages in northeastern Gabon.

An exhaustive epidemiologic and serologic survey was carried out in five gold-panning villages situated in northeastern Gabon to estimate the degree of exposure of to leptospirosis and Ebola virus. The seroprevalence was 15.7% for leptospirosis and 10.2% for Ebola virus. Sixty years after the last seroepidemiologic survey of leptospirosis in Gabon, this study demonstrates the persistence of this infection among the endemic population and the need to consider it as a potential cause of hemorrhagic fever in Gabon. There was no significant statistical correlation between the serologic status of populations exposed to both infectious agents, indicating the lack of common risk factors for these diseases.

Ebola hemorrhagic fever outbreaks in Gabon, 1994-1997: epidemiologic and health control issues.

From the end of 1994 to the beginning of 1995, 49 patients with hemorrhagic symptoms were hospitalized in the Makokou General Hospital in northeastern Gabon. Yellow fever (YF) virus was first diagnosed in serum by use of polymerase chain reaction followed by blotting, and a vaccination campaign was immediately instituted. The epidemic, known as the fall 1994 epidemic, ended 6 weeks later. However, some aspects of this epidemic were atypical of YF infection, so a retrospective check for other etiologic agents was undertaken. Ebola (EBO) virus was found to be present concomitantly with YF virus in the epidemic. Two other epidemics (spring and fall 1996) occurred in the same province. GP and L genes of EBO virus isolates from all three epidemics were partially sequenced, which showed a difference of <0.1% in the base pairs. Sequencing also showed that all isolates were very similar to subtype Zaire EBO virus isolates from the Democratic Republic of the Congo.

Seroprevalence of four sexually transmitted diseases in a semi-urban population of Gabon.

Using the cluster-sampling method, the authors estimated the seroprevalence of 4 sexually transmitted diseases (STDs) among the sexually active general population in a city of 30,000 inhabitants in the east of Gabon. The seroprevalences were 2% for HIV-1, 13.8% for hepatitis B, 8.6% for Treponema pallidum and 59.6% for Chlamydia trachomatis. The seroprevalences of hepatitis B and chlamydia were stable over time and similar to those registered in other countries of central Africa. On the other hand, the seroprevalence of T. pallidum is notably low in comparison with these countries and seems to be decreasing. The seroprevalence of HIV-1 is also low but has doubled in 8 years in the city. Immigrant women from west Africa were a high-risk group for STDs but more generally, cohabiting was a risk factor for women.

PIP: Findings are presented from a seroprevalence survey of HIV, hepatitis B, syphilis, and chlamydia conducted in Franceville, Gabon, during 2 days in January 1996, in a representative sample of the sexually active general population aged 14-55 years. 456 usable sera were collected from 457 individuals recruited in 20 clusters of 25 people each. Franceville is a city of approximately 30,000 inhabitants. 2% were infected with HIV-1, 13.8% with hepatitis B, 8.6% with Treponema pallidum, and 59.6% with Chlamydia trachomatis. The seroprevalences of hepatitis B and chlamydia were stable over time and similar to those reported in other central African countries. However, the seroprevalence of T. pallidum is quite low relative to those other countries and appears to be decreasing. The seroprevalence of HIV-1 is also low, but twice the level observed in 1988.