Japan is facing a major outbreak of pharyngoconjunctival fever, more commonly known as pool fever, as many people are being infected with the virus in public swimming pools, the National Institute of Infectious Diseases said Saturday.

The institute is urging people to take a full shower before and after swimming in pools and to refrain from sharing towels to prevent infection.

According to a survey at some 3,000 medical facilities nationwide, the number of people suffering from the virus has increased since May. It reached 0.65 patient per medical facility in the week from July 7 to 13, the highest figure during the past 10 years.

The number rose further, hitting 0.77 in the week from July 14 to 20, the institute said, adding that more than 70 percent of the patients are children under the age of 5.

Symptoms of pool fever include a high fever and sore throat. In many cases, patients are infected after absorbing contaminated pool water through the eyes and mouth. Sharing towels increases the risk of infection.