Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus in Mui Island, Rural Area, Incheon, South Korea

Abstract

The rural areas are the main outbreak sites of severe fever with thrombocytopenia syndrome (SFTS). To identify the seroprevelance of SFTS in rural island, we conducted a serosurveillance study of SFTS virus (SFTSV) of the general public in Mui Island, a representative rural island of Incheon, South Korea. A total of 203 participants (female 127, male 76, 30 to 97 years old, median 67) without symptoms or signs of SFTS were collected via a convenience sampling. Nested reverse transcription PCR was conducted for both the S and M segments of SFTSV gene. Indirect immunofluorescence assay was also performed for immunoglobulin G (IgG) and immunoglobulin M (IgM) against SFTSV. Only 1 participant (0.5%) was positive to SFTSV gene without IgM against SFTSV. In addition, 12 participants (5.9%) were positive to IgG against SFTSV. Seropositive rate of IgG against SFTSV was higher in age group >65 than ≤65 (9.6% vs . 1.1%, OR 9.202; 95% CI, 1.165–72.692; p=0.026) and was not statistically significant according to sex, occupation and duration of residence in Mui Island. This study suggests that SFTSV readily have infected humans in the rural island of Incheon, South Korea. Therefore, reinforced surveillance about SFTS is needed, focusing on medically vulnerable area such as an island. This is the first seroprevalence report of SFTSV in the rural island of Incheon, South Korea. We found the seroprevalence of SFTSV gene 0.5% (1/203, 95% CI, 0.01–2.7%) and SFTSV antibodies 5.9% (12/203, 95% CI, 3.1–10.1%) among the general population on Mui Island, Incheon, South Korea. This study is significant in that it confirmed the seroprevalence of asymptomatic SFTS in the rural island, a medically vulnerable area. So far, no SFTS patients have been reported in Mui Island. This may suggest a lack of proper infectious diseases surveillances and patient reporting in areas with very low access to health care.