No meningitisx Relative humidity

Fig. 13.4. The seasonal variation of meningococcal meningitis in relation to relative humidity in the Sahel region of Africa.

the northern boundary is the desert. Within this area, major epidemics, mainly of group A, occur at 7-14-year intervals, with lesser ones in between.

In addition to the meningitis epidemic belt in Africa, there have also been epidemics of group A organisms in India and Nepal, and group B in the Americas, Europe and Pacific Island Nations.

Epidemic meningitis is commonest in the age group of 5-15 years, with males more frequently affected than females. Only about one in 500 persons infected with the organism will develop meningitis. Large, poor families and other conditions where there is overcrowding, such as religious and social gatherings, refugee camps and labour lines, make meningitis more likely.

Control and prevention Overcrowding encourages the transfer of the infecting organism and the carrier state, as well as increasing the dose of bacteria that may be transmitted. All efforts should be made to reduce overcrowding. It may be necessary to close schools and reduce congregation of people, such as in markets and religious gatherings. In the long term, improvement of housing and family planning will have an effect.

Chemoprophylaxis should be given to close contacts, such as all family members, school friends and anyone sharing in a large communal sleeping place (such as a dormitory). Rifampicin 10mg/kg twice daily for 2 days, or if still sensitive to sulphonamides, sulphadiazine 150mg/kg for 2 days can be used. Chemoprophylaxis is not recommended in large epidemics.

There are several vaccines containing either A and C, or A, C, Y and W135. Unfortunately, the very young and those with acute malaria develop reduced immunity. There is also a genetic variation with some ethnic groups having a poor response. Due to these different factors, duration of immunity varies from 3 years or less in young children and must be measured for each community when formu lating a vaccination programme. Vaccine can be used to immunize those most at risk concentrating on the 2-20-year age group and household contacts of cases. When there is an epidemic, mass vaccination should be given to communities in the affected area, including vaccinating children below 2 years of age. It has been suggested that an incidence of 15 cases per 100,000 in a well-defined population for 2 consecutive weeks heralds the beginning of an epidemic and the need to start mass vaccination.

A conjugated C vaccine has been found to be effective in all age groups, especially young children, and in countries where group C meningococcal disease is an important health problem it could be included in the national childhood vaccination programme. If an epidemic is found to be due to group C, then this vaccine should be used.

Treatment may need to be organized on a massive scale when an epidemic occurs by using dispensers, school teachers or other educated people to care for isolated communities. Temporary treatment centres (schools, churches, warehouses, etc.) may need to be set up, rather than bring people into hospital. Benzyl penicillin or chloramphenicol should be used, but in many countries, resistance to these antibiotics will require the use of cephalosporins. If the organism is unknown, use chloram-phenicol. In epidemics, long-acting chlor-amphenicol in oil preparations, given as a single injection, avoids the problem of repeat injections. Dehydration is common and intravenous fluids may be required initially, followed by frequent drinks administered by an attending adult.

Surveillance The regular epidemics that occur in Africa can be forecast and a state of preparedness put into action. When there is a case of meningitis, all contacts should be examined with nasal-pharyngeal swabs. Subtyping of the organism can assist in mapping out epidemics.

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