Japan Faces Early and Severe Flu Outbreak 2025: Hospitals Overwhelmed, Schools Closed

Japan is battling a severe flu outbreak that has hit the country five weeks earlier than usual, prompting widespread school closures and overwhelming hospitals. On October 3, 2025, health authorities declared a nationwide influenza epidemic after reported cases surged past the official threshold.

According to Japan’s National Institute of Infectious Diseases, influenza cases have risen sharply since late September 2025, with more than 4,000 cases recorded in just one week.

The average number of flu patients per medical facility reached 1.56, far exceeding the epidemic mark of 1.04. This early surge is being described as Japan’s most severe seasonal flu outbreak in several years.

The spike has led to closures in more than 130 schools, kindergartens, and childcare centers nationwide. In Yamagata Prefecture, one primary school was forced to shut entirely after 22 of its 36 students fell ill.

The outbreak is particularly severe in Okinawa, Tokyo, and Kagoshima, with 28 of Japan’s 47 prefectures reporting rapidly rising case numbers.

Hospitals are struggling to cope with the influx. Emergency rooms are packed, waiting times are long, and some medical centers report staff shortages as healthcare workers themselves fall sick.

Influenza, commonly known as the flu, is a contagious respiratory infection caused by influenza viruses targeting the nose, throat, and lungs.

It ranges from mild to severe, sometimes leading to hospitalization or death. Transmission primarily occurs through microscopic droplets expelled when infected individuals cough, sneeze, or talk.

Importantly, people may become contagious before symptoms even appear and remain so for several days afterward.

Annual vaccination remains the first and most effective defence, coupled with hygiene measures like handwashing, covering coughs, and avoiding close contact with the sick. ¹

People infected with influenza may experience a range of symptoms that can appear suddenly and vary in intensity. These include:

• Fever or chills, though some people with flu may not develop a fever.

• Cough, often dry and persistent.

• Sore throat and irritation in the upper airways.

• Runny or congested nose

• Muscle and body aches, sometimes severe.

• Headaches that can accompany fatigue.

• Extreme tiredness or weakness

• Vomiting and diarrhea, which are more likely in children than adults.¹

Health experts say the outbreak’s early timing and intensity may point to multiple contributing factors. The return of large-scale tourism and relaxed COVID-era precautions have likely increased viral transmission.

Professor Yoko Tsukamoto from the Health Sciences University of Hokkaido said the flu virus might be adapting to new environments, making it spread more easily. She added that recent shifts in global travel and climate could be altering the traditional flu season.

While there is no confirmed evidence of a major mutation or vaccine resistance, researchers are closely monitoring the virus’s genetic changes. Japan’s health authorities have urged continued surveillance to determine whether an evolving strain could be responsible for this year’s early onset.

• Annual vaccination is recommended since flu viruses evolve rapidly and immunity decreases over time.

• Influenza vaccines are the most effective way to prevent infection and its complications.

• Common types include:

  • Inactivated injectable vaccines (trivalent or quadrivalent).

  • High-dose vaccines designed for older adults.

  • Live-attenuated and recombinant vaccines, available in certain regions.

• Effectiveness may vary yearly, depending on how well vaccine strains match circulating viruses.

• Safety record: Influenza vaccines have been used for over 60 years with a strong safety profile.

• Mild side effects like soreness, fatigue, or low fever may occur, but serious adverse reactions are rare. ²

In response, the government and local authorities are ramping up vaccination campaigns and urging citizens to take preventive steps. Officials are emphasizing mask-wearing, regular handwashing, and early medical consultation for anyone showing flu-like symptoms.

Schools and workplaces have been advised to implement flexible attendance policies to prevent further spread. Elderly citizens, young children, and individuals with chronic illnesses are being prioritized for flu shots as they face a higher risk of complications.

Public health experts also recommend avoiding crowded indoor spaces, improving ventilation, and staying home during illness to protect vulnerable populations.

References:

1. Centers for Disease Control and Prevention. “About Influenza (Flu).” Last updated 2025. Accessed October 11, 2025. https://www.cdc.gov/flu/about/index.html.

2. World Health Organization Regional Office for the Eastern Mediterranean. Influenza Vaccines. Last modified October 11, 2025. https://www.emro.who.int/health-topics/influenza/influenza-vaccines.html?ua=1.

(Rh/Eth/ARC/MSM)