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Chickenpox Outbreak Investigation: A Case Series Study at Eradah Complex for Mental Health. Riyadh, 2018.


On 5th December 2018, the Field Epidemiology Training Program (FETP) was notified of a varicella outbreak in a female psychiatric ward in the Eradah Complex for Mental Health in Riyadh. We investigated to describe the source and scope of the outbreak, the mode of transmission, and identify challenges in case man-agement and outbreak control in this unique healthcare setting.


We conducted an observational descriptive case series study. We de-fined varicella's suspected case as a patient with sudden onset of disease with mild fe-ver, generalized maculopapulovesicular rash with no apparent cause. Confirmed cases also had to be confirmed by the laboratory testing or epidemiological link. We reviewed patients' records and the retrieved data on demographics, symptoms, and vaccination status.


We identified a total of 9 confirmed cases of varicella (5 admitted patients, 4 staff) and one suspected case. The mean age of cases was 35.5 years (range = 25-48 years), 56% of cases were Saudi. All cases were epidemiologically linked: The incuba-tion period ranged from 8-17 days (average of 14 days). 100% had a maculopapular rash, 78% had vesicles, and 56% had a fever. The index case of this outbreak was most likely a nurse diagnosed with varicella on 17 September. The secondary attack rate was 10%.22 % of reported cases had previous varicella vaccination. All cases recovered without any complications.


Based on symptoms, incubation period, the epidemiological investigation, we found evidence of probable nosocomial transmission of varicella virus from person-to-person between the staff and the patients due to close contact. We recommended screening of exposed patients and staff, vaccination of those who have negative vari-cella serology, affording isolation rooms for females' wards and continuous follow-up until no new case appears for 42 days (2 incubation periods) after the rash onset of the last identified case to ensure that the outbreak has ended.