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The study examined the seasonal pattern of larvae, nymph, and adult life stages for Haemaphysalis longicornis and the rate of infection with severe fever from the thrombocytopenia syndrome virus in ticks collected from 12 sections (Jichukdong), 14 sections (Uldaeri), and 18 sections (Howondong) in Bukhansan dullegil for April–October 2019. Haemaphysalis longicornis ticks have been considered the main vector for severe fever with thrombocytopenia syndrome (SFTS). Haemaphysalis flava and Ixodes nipponensis were collected using the dragging and flagging method. The ratios of Haemaphysalis longicornis of the collected ticks were 91% (Jichukdong), 94% (Uldaeri), and 98% (Howondong). Monthly distributional studies of Haemaphysalis longicornis based on the developmental stage showed that the adults peaked in September while nymphs were collected more frequently from April through June. The larvae peaked in September and October. SFTS virus detection was performed using 2 × OneStep RT-PCR and nested PCR. On the other hand, no SFTS virus-specific gene was detected in 1,158 ticks of Haemaphysalis longicornis. This result provides estimates of the population densities for the life stages of Haemaphysalis longicornis and the associated disease risk in Bukhansan dullegil, where many people have visited since opening in 2010.

Severe fever with thrombocytopenia syndrome (SFTS) is a newly emerging infectious disease, caused by a novel species of Phlebovirus of Bunyaviridae family, in China, South Korea, and Japan. SFTS is primarily known as a tick-borne disease, and human-to-human transmission is also possible in contact with infectious blood. Common clinical manifestations include fever, thrombocytopenia, and leukopenia as initial symptoms, and multiple organ dysfunction and failure manifest with disease progression. Whereas disease mortality is reported to be 12% to 30% in China, a recent report of cumulative SFTS cases indicated 47% in Korea. Risk factors associated with SFTS were age, presence of neurologic disturbance, serum enzyme levels, and elevated concentrations of certain cytokines. Diagnosis of SFTS is based on viral isolation, viral identification by polymerase chain reaction, and serologic identification of specific immunoglobulin G. Therapeutic guideline has not been formulated, but conservative management is the mainstream of treatment to prevent disease progression and fatal complications.