Korea has confirmed its first locally acquired human case of Oz virus infection, a rare tick-borne disease previously reported mainly in Japan, health authorities said Thursday.
Korea has confirmed its first locally acquired Oz virus infection in an elderly woman who tested negative for SFTS but was later found to have the tick-borne virus during follow-up surveillance. (Credit: Getty Images)
The case involved a woman in her 80s who developed fever, chills and muscle pain in November last year and was initially tested for severe fever with thrombocytopenia syndrome, or SFTS. Although the SFTS test came back negative at the time, the Korea Disease Control and Prevention Agency (KDCA) later identified Oz virus in her sample during an additional analysis of SFTS-negative specimens in March.
The patient had no history of overseas travel and was found to have worked only in a small garden near her home before developing symptoms. She received treatment and was discharged safely, according to the agency.
The case marks the first detection of Oz virus in a patient without overseas travel history in Korea. The country previously reported one imported case in July 2023 involving a person believed to have been infected while traveling in Japan.
Oz virus is a tick-borne virus first identified in 2018 from Amblyomma testudinarium ticks collected in Japan’s Ehime Prefecture. The virus drew attention in 2023 after Japan reported a fatal human infection, raising concern that it could cause illness in humans despite its limited global case record.
The KDCA said it has been strengthening surveillance for unexplained tick-borne febrile illnesses as climate change alters the habitats of disease-carrying vectors such as ticks. As part of the program, the agency conducts additional quarterly testing on samples that test negative for SFTS to monitor whether emerging infections reported in neighboring countries, including Japan and Taiwan, are being introduced into or occurring in Korea.
The latest case was found during such follow-up testing, which screened SFTS-negative samples for about 10 viruses. The agency said it established a genetic detection test for Oz virus in 2023 to prepare for possible domestic introduction.
“Oz virus infection should be considered in patients who develop fever after tick exposure when the cause is unclear,” KDCA said. “Because its main symptoms, including fever, chills and muscle pain, overlap with those of SFTS, clinical symptoms alone may not be enough to distinguish between the two diseases, making additional diagnostic testing necessary.”
Lee Han-soo
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