A study on relationship between the incidence of measles and nosocomial exposure at measles epidemic season in Chongqing

After measles vaccine supplementary immunization, the epidemiological characteristics of measles have changed in Chongqing, China. In addition, according to data from the National Measles Surveillance Information System, the proportion of measles cases with a history of hospital visit 7 to 21 days prior to onset of measles increased year by year to 32.1% in 2016. Further studies are necessary to eliminate the influence of nosocomial exposure on measles. We performed a case-control study in seven districts of Chongqing from June to August 2016 to identify risk factors for measles virus infection and susceptibility. Laboratory-confirmed measles who younger than 5 years old were matched with one control by age and residence. We interviewed case patients and controls regarding potential risk factors for measles virus infection and susceptibility. Unadjusted and adjusted matched odds ratios and 95% confidence intervals (CIs) were calculated using non-conditional logistic regression. After a cross-sectional analysis of the behavioral characteristics of visiting hospitals in the case and control groups, it was found that there was a difference between the two groups in the choice of hospitals visited for the first time (χ(2) = 35.500, P = .000), and that nosocomial transmission risk tended to develop in outpatient services of respiratory medicine. After analysis using one-way ANOVA, the relationship between hospital visits prior to onset and the incidence risk of measles was that visiting hospitals five times within 1 to 3 weeks prior to onset affected the incidence (OR = 44.866, 95%CI = 5.938–338.981). The relationship between the number of types of hospitals visited prior to onset and the risk of nosocomial exposure to measles showed that visiting any community hospital, children’s hospital, or general hospital had no risk, but visiting two or more of these hospitals affected the incidence (OR = 6.928, 95%CI = 3.849–13.754). Based on further analysis, the relationship between the number of hospital visits after onset and the risk of nosocomial exposure to measles was that the chances of visiting hospitals increased after onset. Risks of nosocomial exposure to measles and infections are high in pediatric hospitals. Nosocomial exposure risk factors should be considered when controlling measles.