Academic journal article Bulletin of the World Health Organization

Epidemiology of Meningitis Due to Haemophilus Influenzae Type B in Children in Bulgaria: A Prospective, Population-Based Surveillance Study. (Research)

Academic journal article Bulletin of the World Health Organization

Epidemiology of Meningitis Due to Haemophilus Influenzae Type B in Children in Bulgaria: A Prospective, Population-Based Surveillance Study. (Research)

Article excerpt


Globally, Haemophilus-influenzae type b (Hib) is one of the leading causes of bacterial meningitis in children <5 years of age, and safe and effective vaccines are available to prevent this disease (1). Little information is available on the disease burden due to Hib in certain regions of the world, however, and the World Health Organization (WHO) has recommended that efforts be made to evaluate the magnitude of Hib meningitis in these areas. Among the 26 countries classified by the United Nations as economies in transition (a) (2)--which include the Baltic States, Central and Eastern Europe (Bulgaria is within this group) and the Commonwealth of Independent States--only one country (Slovenia) has published results from a population-based study of the incidence of Hib (3).

In Bulgaria, a retrospective review of bacterial meningitis in the six largest regions in the country during 1992-96 showed a relatively low annual incidence of Hib meningitis: 1.3-11.0 per 100 000 children <5 years of age (Kojouharova, unpublished data, 2000). This study was unable to assess fully the meningitis case-fatality rates. The retrospective study found an incidence of Hib meningitis lower than that found in similar studies before Hib vaccine was introduced in Scandinavia (4) and the United Kingdom (5), but it was unclear whether this difference was due to limitations in surveillance, problems with diagnostic methods, more extensive use of antibiotics in Bulgaria or a true paucity of Hib infection in the Bulgarian population. During 1997-99 we conducted a prospective, population-based surveillance study in the same regions of the country as the 1992-96 retrospective study, to better assess the burden of Hib meningitis, including the case-fatality rate, and to provide evidence for an informed decision about the use of Hib vaccines in Bulgaria.


Bulgaria is a central Balkan country with a population of 8.2 million, a birth rate of 7.9 per 1000 population, and an infant mortality rate of 14.3 per 1000 live births (6). The country has 28 regions. The study was carried out between 1 July 1997 and 31 December 1999 in the six largest regions: Pleven Region, Plovdiv Region, Sofia City, Sofia Region, Stara Zagora Region and Vama Region. The study population consisted of 138 249 children aged <5 years--a sample that represented 40% of the nationwide total of 348 000 children in this age group. The study received ethical approval from the Scientific Council of the National Center of Infectious and Parasitic Diseases in Bulgaria and from the WHO Secretariat Committee on Research Involving Human Subjects. Informed consent was not required, because lumbar puncture for children with suspected meningitis is the routine standard of care in Bulgaria.

This prospective study was based on two documents produced by WHO: a generic protocol for population-based surveillance of Hib meningitis (7) and a manual of microbiological methods (8). Bulgarian versions of these documents were distributed to physicians, public health officials and microbiologists in the six study regions to ensure standardization of surveillance and laboratory procedures. One physician-epidemiologist and one microbiologist from each study region participated in a pre-study workshop on meningitis surveillance and laboratory methods held in Sofia on 12-15 May 1997. The workshop was organized by the National Center of Infectious and Parasitic Diseases, Sofia, and it received technical support from WHO and the United States Centers for Disease Control and Prevention.

In Bulgaria, meningitis is an officially reportable disease, with notification of each suspected case to the regional epidemiology office required within 24 hours. Routine surveillance for infectious diseases includes daily case reports from hospitals and clinics, telephone feedback to referring physicians and case investigations by teams of physician-epidemiologists at the regional epidemiology office. …

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