Objective To examine an incidence of Chikungunya fever and Chikungunya virus (CHIKV) infection among members of an outbound touring group and to evaluate local transmission risk of the imported case.
Methods Follow-up surveys were carried out among all members (n = 20) of a touring group travelling to Mandalay and Bagan of Burma and returning to Shandong province, China during September 18 – 21, 2019. Twenty blood and 17 urine samples were collected among the members for the detection of nucleic acid and specific immunoglobulin M (IgM) antibody of CHIKV. And the regional mosquito vector density of the core epidemic area was estimated with double-stack ledger and the Breteau index method. Fourteen days later, the blood samples of the members were collected again for the detection of serum immunoglobulin G (IgG) antibody.
Results The imported case was a 35 years old Chinese man with serum positive for CHIKV nucleic acid detected 3 days after the end of the travelling. Of all the members of the touring group, 85% reported the history of mosquito bites. No serum CHIKV nucleic acid positive sample was detected except for the sample from the case. The outdoor Breteau index in the case-relaed core epidemic area was 5.38, which exceeded the transmission threshold and indicated a risk of disease transmission. All the blood samples were negative for serum IgM antibody and only the case′s blood sample was positive for serum IgG antibody.
Conclusion There is a risk of imported case-related local transmission of Chikungunya virus in Shandong province and relevant prevention measures should be promoted.
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