As the nation enters the autumn tourist season, concerns are growing over hornets, whose nests and number of workers are larger than usual this year because of the warmer spring and limited rain during the rainy season.
Hornet stings have been reported in Gifu and Nagano prefectures since August. Experts warn that worker hornets tend to become more aggressive when there are more of them, and in autumn when they need to protect the larvae that will become their new queens.
Hornet stings can cause anaphylaxis, including shortness of breath and vomiting, and at times can be life-threatening. Twenty-three people died due to bee stings in 2015, 19 in 2016 and 13 in 2017, according to the health ministry's demographic statistics.