Surveillance of respiratory viruses

Respiratory virus isolates made at the National Institute for Virology from 1982 to 1991 were studied. An active virus surveillance programme, 'viral watch', which recruits throat swab specimens from a network of monitoring centres - mainly in the Witwatersrand and Vereeniging area with one centre in Middelburg - that represent a cross-section of the population, provided 68% of the specimens and 74% of the isolates, with an isolation rate of 25,5%. This was significantly higher than that of routine specimens (17,7%). Of the 966 isolates, influenza viruses accounted for 527 (54,7%), para-influenza for 122 (12,6%), respiratory syncytial virus for 34 (3,4%) and adenovirus for 106 (11,0%). Influenza viruses showed a definite seasonal peak between June and August whereas the other viruses, although they showed a winter predominance, were isolated throughout the year. An active virus surveillance programme is particularly valuable in monitoring respiratory virus epidemiology in the population

Primary and secondary infection with human parvovirus B19 in pregnant women in South Africa

A study of human parvovirus B19 infection in 1 967 pregnant women of all races in Johannesburg revealed an overall prevalence of 24,9% for IgG antibodies and 3,3% for IgM antibodies. Of the 64 IgM-positive sera indicating active infection, 62 were resistant to urea denaturation. No differences in the prevalence of IgG antibodies between population groups were observed, but active infections, as demonstrated by IgM antibodies, were significantly more prevalent in black than in white, coloured or Asian mothers

Hepatitis B virus prevalence in two institutions for the mentally handicapped

A comparative study of the prevalence of hepatitis B virus infection in two institutions for the mentally handicapped was carried out between April and November 1989 and April and August 1991. The institutions were situated within 10 km of each other in north-eastern Johannesburg. One institution had a significantly higher prevalence of virus markers, 68% (139 of 203) compared with 23% (40 of 176), was in poorer condition and had more severely handicapped residents with more aggressive behaviour. However, the most important difference between the two institutions was that residents at the higher-prevalence institution were admitted at a considerably younger age. Younger individuals appear to be more susceptible to infection and are more likely to develop persistent infection, thus contributing to a greater pool of infection in the institution

Should pregnant urban South African women be screened for hepatitis B?

The prevalence of hepatitis B virus (HBV) infection in the South African urban obstetric population, which consists of white, black, coloured and Asian patients from different socio-economic, cultural and geographical backgrounds, is unknown. Routine screening performed in 3 469 urban pregnant women revealed that 42 patients were HBV surface antigen-positive (a prevalence of 1,21%). Only 2 patients (4,6%) were hepatitis B e antigen (HBeAg)-positive (0,06% of the entire cohort), whereas the remaining 40 were identified as hepatitis B e antibody-positive. Despite a significant increase in the numbers of black patients, there has not been an accompanying increase in the number of HBV carriers. Replicative infection was equally distributed among white and black pregnant women

Benefits and limitations of the Witwatersrand influenza and acute respiratory infections surveillance programme

Objective: To establish an ongoing active surveillance programme for acute respiratory infections in general, and influenza in particular.Design: A network of 16 sentinel primary health care providers furnished morbidity information and clinical specimens for virus characterisation supplemented by school absenteeism and regional mortality data.Setting: General practices, hospital outpatient departments and staff clinics in the Witwatersrand area.Participants: Subjects treated for acute respiratory infections by 7 general practitioners, 1 specialist pulmonologist,4 paediatric outpatient departments, 1 mine hospital and university, factory and institutional staff clinics. Absenteeism data were obtained from 8 primary and 6 high schools in the region (representing 9 000 pupils}.Outcome measures: Morbidity information and strain characterisation of influenza isolates as well as other viral respiratory pathogens, school absenteeism, seasonal excess mortality.Results: The most sensitive indicator of influenza activity was virus isolation, which gives an earlier warning signal of an impending epidemic than morbidity or absenteeism parameters. Both morbidity and school absenteeism provided quantitative indicators of the severity of the epidemic. Mortality from all causes showed characteristic winter increases in the 65-year-old and older population which were not seen in younger individuals. Circulating influenza viral strains matched the strains recommended for the vaccine in 1991 and 1992, but not in 1993.Conclusions: The course and extent of the annual winter influenza epidemic can be charted by means of an active surveillance programme, with sentinel primary health care providers furnishing morbidity data and clinical material from which virus isolations can be made. Antigenic characterisation of the isolates demonstrated that circulating strains may not match recommended strains in northern hemisphere-formulated vaccines and stresses the need for a southern hemisphere vaccine formulation for South Africa. Absenteeism information provides an indicator of the impact of influenza on the economy and excess mortality data emphasise the need for routine immunisation of the elderly

Is antenatal screening for rubella and cytomegalovirus justified?

Altogether 2 250 asymptomatic pregnant women attending an antenatal clinic were investigated for serological evidence of past exposure to rubella and cytomegalovirus (CMV) as well as for active primary infection or reinfection/ reactivation. Only 7 (0,3%) active rubella infections were diagnosed, none of them primary. Similarly, out of 132 patients with active CMV, only 5 primary infections (3,8%) were diagnosed; the vast majority 127 (96%)- had reactivation infections. No congenital rubella infections were detected, while the transplacental transmission rate for CMV was 6,4%. None of the infants followed up was clinically affected at birth or at 6 months. No racial differences in seroprevalences for CMV or rubella immunoglobulin were observed, but immunoglobulin antibody prevalence to CMV was significantly lower in the white group. From this study there appeared to be no indication for routine antenatal screening for CMV in asymptomatic mothers