Six recent cases of severe fever with thrombocytopenia syndrome during the 2024 - 2025 in Kochi, Japan: A possible surge and clinical clue for early recognition.

OBJECTIVES

To characterize recent clinical features of severe fever with thrombocytopenia syndrome (SFTS) in an endemic region of Japan, emphasizing the importance of early clinical recognition.

METHODS

We retrospectively analyzed six consecutive adult patients with SFTS diagnosed at Kochi Health Science Center (Kochi, Japan) between 2024 and June 2025. Diagnosis was confirmed by real-time polymerase chain reaction testing, and viral load was quantified. Patient characteristics, animal exposure history, and laboratory findings were summarized.

RESULTS

Symptom onset occurred between March and November. Four patients had no tick bite marks, while three had recent cat exposure. All patients exhibited thrombocytopenia, elevated liver enzymes, and a slight elevation of serum C-reactive protein. Favipiravir was administered in all cases, with five recoveries. One patient developed hemophagocytic syndrome despite a moderate viral load.

CONCLUSIONS

In endemic and warm-climate regions, SFTS should be suspected year-round. Key clinical features, including cat exposure, thrombocytopenia, and a slight elevation of serum C-reactive protein, may aid early diagnosis even in the absence of tick bite history.