Mycoplasma pneumonia is spreading in Japan. The weekly average number of patients reported by medical institutions across the country has risen for five weeks in a row and hit an all-time high in late September.

Mycoplasma pneumonia is a respiratory infection caused by bacteria. Children are more likely to become infected.

It spreads through water droplets and physical contact, and is characterized by such symptoms as fever, fatigue, headache and coughing that could last for more than a week. Some patients could require hospitalization due to severe pneumonia or weakness.

Data from the National Institute of Infectious Diseases shows that the average number of cases reported by about 500 medical institutions was 1.64 per institution per week through September 29.

The figure is the highest since data was first collected by the current method in 1999. It exceeds the 1.61 logged during a major outbreak in October 2016.

Fukui Prefecture had an average 5.33 patients per institution, followed by Saitama at 4.25 and Gifu at 3.4.

Professor Izumikawa Koichi of Nagasaki University Hospital said the number of patients could rise further during the coming winter, as people tend to stay in less ventilated rooms. He stressed the importance of wearing face masks and other anti-infection measures.

He advised that people should see a doctor early if they have a persistent fever or coughing, adding that the coughing could worsen and keep them from sleeping.