Epidemiology of Meningitis

Epidemiology refers to the study of distribution and determinants of disease conditions. Bacterial meningitis remains a serious threat to global health, accounting for an estimated annual 170,000 deaths worldwide.  Even with antimicrobial therapy and the availability of sophisticated intensive care, case fatality rates remain at 5–10% in industrialized countries.  All forms of meningitis occur in Africa.  Meningococcal meningitis can occur sporadically or in the form of epidemic outbreaks, especially in crowded institutions such as barracks, refugee camps and prisons.  Very large epidemics often sweep across Africa along the so called “Meningitis Belt”,  an area stretching from  Senegal in the west to Ethiopia in the east,  and also moving into Sudan, northern Uganda, Ethiopia, northern Kenyan, northern Tanzania

In 1996, Africa experienced the largest recorded outbreak of epidemic meningitis in history, with over 250 000 cases and 25 000 deaths registered. Between that crisis and 2002, 223,000 new cases of meningococcal meningitis were reported to the World Health Organization. The countries most affected countries have been Burkina Faso, Chad, Ethiopia and Niger; in 2002, the outbreaks occurring in Burkina Faso, Ethiopia and Niger accounted for about 65% of the total cases reported in the African continent. Furthermore, the meningitis belt appears to be extending further south. In 2002, the Great Lakes region was affected by outbreaks in villages and refugees camps which caused more than 2,200 cases, including 200 deaths.

In major African epidemics, attack rates ranges from 100 to 800 per 100 000 population, but individual communities have reported rates as high as 1000 per 100 000. While in endemic disease the highest attack rates are observed in young children, during epidemics, older children, teenagers and young adults are also affected.

About 10-20% of those who survive a meningitis  attacks develop complications such as epilepsy, mental retardation or sensorineural deafness.

Three species, Haemophilus influenzae, Streptococcus pneumoniae and  Neisseria meningitidis, are responsible for most cases of bacterial meningitis occurring beyond the neonatal period.

Major African epidemics are associated with N. meningitidis serogroups A and C and serogroup A is usually the cause of meningococcal disease in Asia. Outside Africa, only Mongolia reported a large epidemic in the recent years (1994-95).

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