Japan's health ministry says an influenza outbreak has now spread across the country, with the estimated number of patients exceeding 2.1 million.
The ministry says the average number of patients at around 5,000 medical facilities nationwide was 53.91 in the week through last Sunday.
That's up 15 from a week before and the second-highest figure since the ministry began taking data in 1999.
The three most severely affected prefectures are Aichi, Saitama and Shizuoka.
The ministry says the H1N1 strain accounts for about 60 percent of the cases. The strain caused a global outbreak of a new influenza a decade ago.
The ministry warns that more people could contract the flu, and is urging people to take preventive measures such as washing hands and wearing surgical masks.