An outbreak of varicella caused by herpes zoster in a welfare house

  Objective  To analyze the investigation and response of an outbreak of varicella caused by herpes zoster case in a social welfare house and provide reference for the prevention and control of similar outbreaks.

  Methods  The case definition was developed, and the health monitoring forms, attendance records and the infectious disease surveillance system of the welfare house were checked. Active case finding and investigation were conducted. Descriptive epidemiological methods were used to analyze the epidemiological characteristics of the epidemic.

  Results  From March 28 to April 28, 2020, a total of 1 case of herpes zoster and 17 cases of varicella occurred in the welfare house. The attack rate of varicella was 27.87% (17/61), and the attack rate in children living in the welfare house was 55.56% (15/27), higher than that in workers (5.88%, 2/34), the difference was significant (χ²=18.47, P＜0.001) . Among the children living in the welfare house, the attack rate in those aged ≤14 years was higher, and the difference was not statistically significant (P=0.45). The rate of varicella vaccination in the children was 11.11%, and the full course immunization rate was only 3.70%. The attack rate in the children without immunization history was 58.33% (14/24), higher than that in those with immunization history (33.33%, 1/3), the difference had no significance (P=0.57). The health status of the children varied, the duration of the illness was 11–41 days, and the illness lasts for a long time. Samples were collected from the index case and 9 clinically diagnosed varicella cases, and these samples were varicella zoster virus (VZV) nucleic acid positive by RT-PCR.

  Conclusion  The source of the varicella outbreak in the welfare house was a nursing assistant suffering from herpes zoster. The health status of the children in the welfare home varied and they had a collective lifestyle, which was the risk factor for the spread of infectious diseases. Increasing the vaccination rate of school-age children, reducing the gaps in immunization, strengthening the prevention and control of infection, and encouraging relevant staff to be vaccinated with zoster vaccine before employment can effectively prevent and control the spread of VZV in welfare house and other similar settings.