The number of weekly pertussis cases reaches a record high of 3,044—Risks and measures that foreigners living in Japan should be aware of now

1. Introduction

A severe cough lasting several weeks without sudden fever—"whooping cough" was once feared as a cause of death among newborns and infants. Since the introduction of vaccines in the 1960s, it has drastically decreased. However, from around autumn 2024, the number of patients began to increase across Japan, setting a new record of 3,044 weekly cases in June 2025. Why is it re-emerging now? We will organize the issues from the perspective of unvaccinated individuals and missed booster shots, particularly among foreigners, and the delay in medical access due to language barriers.news.tv-asahi.co.jpfnn.jp

2. What is Whooping Cough

• Causative Bacterium: Bordetella pertussis

• Incubation Period: 7-10 days (up to 21 days)

• Main Symptoms: Mild cold-like symptoms in the catarrhal stage → paroxysmal stage (with "whoop" sound) → recovery stage

• Complications: Pneumonia, otitis media, seizures, encephalopathy

• Mortality Rate: Up to 1-3% in infants (if untreated)

3. Recent Outbreak Situation

The top three regions are Tokyo, Saitama, and Chiba, and in terms of population per 100,000, Tokushima and Okinawa also rank high. It is important to note that cluster outbreaks are also observed in rural areas.4. Why has it increased?

1. Diminished vaccine immunity
   The fifth additional dose of DPT-IPV (quadrivalent) is optional, resulting in low antibody levels among middle and high school students.
   
   

2. Missed vaccinations post-pandemic
   Many families avoided visiting medical institutions during the COVID-19 pandemic, leading to significant delays in vaccination schedules for infants.
   
   

3. Resumption of international travel
   An increase in imported cases from countries with outbreaks, spreading through conferences and sports events.
   
   

4. Genetic mutations of pathogens
   According to a CDC report, variants with different antigenicity from the conventional vaccine strains have been detected.

5. People who are more susceptible

• Infants (0-6 months) : High mortality rate due to incomplete vaccination.

• Pregnant women : Risk of premature birth due to coughing fits.

• Elderly and asthmatics : Rib fractures or severe pneumonia due to coughing.

• Healthcare and education workers : Likely to become hubs for infection chains.

6. Comparison with overseas

• In Australia , weekly cases reached 1,200 in March 2025, leading to the reintroduction of mandatory masks in elementary schools.

• In the United States , sporadic resurgences occur by state, and the CDC is considering shortening the Tdap booster interval from the traditional 10 years to 5 years.

• In the EU , a large outbreak occurred in Germany in the winter of 2024, prompting a free vaccination campaign for adults.

7. Advice for foreign residents in Japan

8. Government and Local Authorities' Response

• Ministry of Health, Labour and Welfare Notice (dated 6/17): Request for a wide-area testing system to all medical institutions nationwide.

• School Health and Safety Act: Enforce guidance for suspension of attendance until symptoms subside (approximately 5 days).

• Local Governments: Temporary vaccination subsidies have started in Tokushima and Okinawa Prefectures.

9. Expert Comments

• Noriko Kawai, Head of the Department of Fetal Infection, National Institute of Infectious Diseases
  "The greatest risk is 'stealth infection' where asymptomatic adult carriers transmit to infants. Strengthen household barriers with booster vaccinations for all family members."
  
  
  

• World Health Organization (WHO) Western Pacific Regional Office
  "Simultaneous outbreaks are increasing in the region, and Japan's data will become an important indicator for enhanced surveillance."

10. Future Outlook and Preparedness

Simulations suggest that if the current pace continues,there is a risk of reaching 5,000 cases per weekby late July. The feasibility of holding large-scale events and the reinstatement of health questionnaires at airport quarantine are being discussed, and individual preventive actions will influence the epidemic curve.

Summary

• 3,044 people/week isthe highest ever.

• Booster vaccinations, masks, and hand hygiene are key.

• Protecting infants and pregnant women from household infections is urgent.
  
  

Reference Article List

1. TV Asahi "Whooping Cough: Weekly Patient Count Reaches 3,044, Exceeding 3,000 for the First Time, Setting a New Record, Ministry of Health, Labor and Welfare" (2025/06/17)news.tv-asahi.co.jp

2. FNN Prime Online "Whooping Cough: New Infection Count Reaches Record High, Exceeding 3,000 in a Week for the First Time" (2025/06/17)fnn.jp

3. TBS NEWS DIG "Whooping Cough: Nationwide Weekly Report Count at 3,044, Highest Since 2018" (2025/06/18)newsdig.tbs.co.jp