Outbreak of Crimean-Congo hemorrhagic fever in Kyzylorda region, Kazakhstan, March-July 2022

Saya Gazezova ^1,2 Malika Gabdullina ¹ Gulzhan Ayapova ^1,2 Dilyara Nabirova ^1,3,4* Michelle Waltenburg ⁵ Manar Smagul ^1,2 Lena Kassabekova ^1,2 Umirbek Ussenov ² Roberta Horth ^1,3

• ¹ Central Asia Field Epidemiology Training Program, Asfendiyarov Kazakh National Medical University, Almaty, Kazakhstan
• ² Scientific and practical center of sanitary-epidemiological examination and monitoring, branch of the National Center for Public Health, Almaty, Kazakhstan, Almaty, Kazakhstan
• ³ Division of Global Health Protection in Central Asia, United States Centers for Disease Control and Prevention, Almaty, Kazakhstan, Almaty, Kazakhstan
• ⁴ Health Sciences Unit, Faculty of Social Sciences, Tampere University, Tampere, Pirkanmaa, Finland
• ⁵ Division of Global Health Protection, Center for Global Health, Centers for Disease Control and Prevention (CDC), Atlanta, Colorado, United States

Background: Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonotic disease with a high case-fatality rate (~30%). CCHF is endemic in Kyzylorda Oblast, Kazakhstan (population: 800,000), with approximately 10 cases annually. In 2022, 15 cases had been reported by the end of July. We investigated to determine risk factors and suggest prevention measures.We conducted a case-control study. Cases were defined as people hospitalized in April-July 2022 with signs consistent with CCHF and history of exposure (contact with ticks or animals and sudden onset of unexplained bleeding) within two weeks before illness. Confirmed cases had CCHF-positive PCR and ELISA IgM and IgG tests. The controls were contacts from two households in the neighboring of each case. We used logistic regression to assess factors associated with CCHF. Ticks collected from animals residing on case-patient's property were tested for CCHF. We reviewed public environmental and livestock data. We studied 17 suspected, seven probable, 14 confirmed case-patients and 71 control persons. Case-patients were predominantly male (74%), 47% were livestock workers and 37% were agricultural workers. Among the 14 confirmed CCHF case-patients, four died (case fatality rate=29%). All (100%) case-patients experienced weakness, 97% had headaches, and 84% had fevers. Fifty-three percent of case-patients reported ticks on their bodies and clothing ≤2 weeks before illness onset compared with 1% of control-persons (p<0.001). Half (47%) of case-patients visited or lived in a high-risk area for tick bites ≤2 weeks before illness onset compared with 6% of control-persons (p<0.001). Livestock and agricultural workers had increased odds of CCHF compared to those not in those professions (odds ratios and 95% confidence interval: 3.