Differences in tuberculosis incidence rates in township and in rural populations in Ntcheu District, Malawi

There has been a large upsurge of tuberculosis (TB) in many countries in sub-Saharan Africa, mainly as a result of the co-existing human immunodeficiency virus (HIV) epidemic. Malawi has had a well-run National TB Control Programme (NTP) with good registration and recording of cases. For some years the NTP has had the impression that TB in the country is concentrated around townships and is less prevalent in the rural areas. This impression was investigated in a rural district (Ntcheu District) in Malawi. Data on new TB cases were collected from the district TB register for the years 1992-96 and average annual TB incidence rates per 100,000 for semi-urban and rural populations were calculated for this period. There was a significantly higher incidence of TB, particularly amongst cases with smear-negative pulmonary TB and extrapulmonary TB, in the semi-urban population compared with the rural population. Possible explanations could be higher HIV seroprevalence rates in semi-urban areas compared with rural areas, under-diagnosis at health centres or poor access to medical facilities for rural people.