Intrafamilial clustering and 4-year follow-up of asymptomatic human T-cell leukaemia virus type I (HTLV-I) infection in Benin (West Africa).

BACKGROUND: Few data exist concerning familial human T-cell leukaemia virus type I (HTLV-I) carrier states and transmission in African countries. Two previous surveys performed in Benin in 1989 and 1990 using a three-level cluster sampling method allowed us to identify HTLV-I positive subjects. The evolution of HTLV-I within the families of these subjects is described over a 4-year period, 1991-1995. METHODS: Since 1991, 37 HTLV-I seropositive subjects, six subjects with indeterminate Western-Blot pattern, and their relatives have been followed up once a year clinically and biologically. RESULTS: Twenty-three mothers in the study group gave birth to 27 children between 1991 and 1995. Among the 13 infants born to the 12 seropositive mothers, two seroconverted before their second birthday. One adult woman whose husband was seropositive developed seropositivity 4 years after marriage. In March 1992, a family case-control study (proband study) was conducted. A seroprevalence of 27.5% was found among 138 relatives of 32 infected subjects and 1.4% among 142 relatives of 32 control subjects. CONCLUSIONS: There is clearly an intrafamilial clustering of HTLV-I in Benin. The annual incidence density of HTLV-I in this cohort is estimated at 6 per thousand.

Investigation on a pertussis outbreak in a military school: risk factors and approach to vaccine efficacy.

INTRODUCTION: Pertussis (whooping cough) is a toxic bacterial infection caused mainly by Bordetella pertussis. In mid-January 2006, several cases of pertussis were diagnosed in a military boarding-school. An investigation was carried out at the end of January to identify the risk factors for infection and to evaluate the efficacy of vaccination. SUBJECTS AND METHODS: Three definitions were used to distinguish the cases; confirmed biologically, confirmed epidemiologically and suspected cases. The risk factor study was carried out after the exclusion of suspect cases. Vaccine efficacy (VE) was evaluated from a case-control study where only biologically confirmed cases were included. For each case, five controls were matched according to age, sex and class. A logistic regression and a conditional logistic regression were performed for the risk factor study and vaccine efficacy, respectively. Statistical analysis was carried out using Stata 9.2 software. RESULTS: A total of 206 cases were included, 17 of them biologically confirmed, 66 epidemiologically and 123 suspected cases. The attack rate was 17.8 per 100. Girls were 1.8 times more likely to catch pertussis (p=0.04), pupils in the first year of college, as well as those in high school were at 5 times greater risk of catching pertussis (p=0.008) than those in the second year of college. For pupils who benefited from at least 5 doses, the VE was at 80% when the last dose dated from less than 6 years earlier. DISCUSSION/CONCLUSION: The attack rate observed in our study was similar to those normally seen during epidemics occurring within a community. Vaccine efficacy declined depending on the time lapse since the last vaccination. Since April 2008, the Public Health Authorities have planned to provide pertussis booster vaccinations for children aged 16-18 who missed those for 11-13-year-old, and for adults aged 26-27 and those who have not been vaccinated for more than 10 years.