Epidemiology of rubella infection in Cameroon: a 7-year experience of measles and rubella case-based surveillance, 2008-2014.

OBJECTIVE: The aim of this study was to estimate the proportion of rubella disease in a measles case-based surveillance in Cameroon prior to rubella vaccine introduction into the national immunisation programme.

DESIGN: This was a cross-sectional study for rubella infection in Cameroon for the period 2008 to 2014.

SETTING: Patients suspected with measles from the 10 regions of Cameroon were recruited according to the WHO measles case definition and were tested for rubella IgM antibodies accompanied with the case report/investigation forms.

PARTICIPANTS: All persons with rash and fever within 14 days of onset of rash according to the standard WHO African Regional Office (WHO/AFRO) case definition for a suspected measles case.

OUTCOME MEASURES: Descriptive analyses and simple logistic regressions were performed. OR were estimated.

RESULTS: A total of 9907 serum samples from people with fever and rash were received in the laboratory from 2008 to 2014. A total of 7489 (75.59%) measles-negative samples were tested for rubella; 699 (9.3%) were positive for rubella IgM antibodies. Logistic regression analysis was done using IgM antibodies detection as the outcome variable. Age, sex and setting were explanatory variables. Logistic regression analysis revealed that, comparing the proportion of rubella IgM seropositivity status by age, the association to a positive rubella IgM increased with age from 1 to 4 years (OR 7.11; 95% CI 4.35 to 12.41; p<0.0001), through 5 to 9 years (OR 13.07; 95% CI 7.93 to 22.93; p<0.001), to 10 to 14 years of age (OR 13.86; 95% CI 8.06 to 25.12; p<0.001). Persons aged ≥15 years were also more likely to have rubella infection than children under one (OR 3.69; 95% CI 1.85 to 7.48; p=0.0001). There were also significant associations with sex, with males being less associated to a positive rubella serology than females (OR 1.33; 95% CI 1.14 to 1.56; p=0.0001). No statistically significant difference in proportion of rubella cases was observed between urban and rural populations (OR 1.11; 95% CI 0.94 to 1.31; p=0.208).

CONCLUSIONS: This study reveals that rubella virus circulates in Cameroon, with important number of cases in children under 15 years. This finding supports the planned introduction of rubella-containing vaccines into the Expanded Program on Immunization.