The 2025 influenza season began early, and Okayama Prefecture issued an “Influenza Advisory” on October 30 and an “Influenza Alert” on November 28. I often hear people around me say they have caught the flu.
The theme of the Kurachu Medical Gathering, a public lecture for local residents held on December 4, 2025, was the timely topic “The Truth About the ‘Scary Story of Influenza.’”
The speaker was Dr. Ishida Tadashi, deputy director of Kurashiki Central Hospital and head of its Department of Respiratory Medicine. Dr. Ishida specializes in respiratory infections and has extensive knowledge of infection control. During flu season, he is interviewed by numerous media outlets and explains the state of the outbreak.
Influenza is a well-known illness, but if it becomes severe, it can be life-threatening. And the risk of severe illness also applies to people under 65 and healthy people without underlying conditions.
Here is a report on the true dangers of influenza discussed in the lecture, the three pillars of influenza prevention (1. antiviral drugs 2. vaccines 3. infection control), and other points to keep in mind to protect your health and that of those around you.
The information presented is current as of the article’s publication in December 2025. Please note that it may differ from current information.
Overview of the Kurachu Medical Gathering, a Public Lecture for Local Residents
The lecture was held on Tuesday, December 4, 2025, at Kokuga Hall in the Kurashiki Central Hospital Preventive Medicine Plaza.
Kurashiki Central Hospital Preventive Medicine Plaza, completed in 2019, supports the health of local residents as a regional disease-prevention hub through services such as health checkups and exercise and health classes.
The Kurachu Medical Gathering, a Public Lecture for Local Residents is held once a month. Doctors from Kurashiki Central Hospital speak at the popular lecture series, explaining common illnesses and health measures in an easy-to-understand way.
Quite a few people attended the lecture. They listened attentively, and the lively question-and-answer session showed how much interest there was.
This Year’s Influenza Trends
The defining feature of influenza in 2025 is that the outbreak began early. Last season, cases surged toward the end of the year, but this season they had already exceeded alert levels in November and are spreading rapidly.
● Which strain is spreading now?
Influenza A (H3N2) is the predominant strain. The types change and alternate from year to year. The A(H3N2) strain is also said to be somewhat less responsive to vaccines in older adults, so caution is needed.
● Forecast: Will influenza B arrive after the New Year?
Forecasts reportedly draw on data from the Southern Hemisphere, including Australia, which enters its cold season six months before Japan. This season, the outbreak peak in Australia lasted a long time, and influenza B also spread, particularly among younger people.
Dr. Ishida cautioned that “forecasts can be wrong,” but said that influenza B may increase after the New Year, prolonging the outbreak.
What Is a “Pandemic”?
The lecture also explained the dangers of a pandemic (a global outbreak) from a historical perspective.
Influenza A viruses undergo small changes (antigenic drift) almost every year, but once every few decades, they can suddenly change into a completely new type (antigenic shift). This gives rise to a new influenza strain. Since almost no one has immunity to it, it can trigger a pandemic that spreads explosively around the world.
Today, pathogens can easily cross borders along with the movement of people. Once an outbreak occurs, it is difficult to contain it completely. That is why it is important to be prepared at all times.
Characteristics of People at Risk of Severe Illness
Many people recover from influenza on their own, but some develop complications that can become life-threatening. The high-risk groups defined by the Infectious Diseases Society of America are as follows.
- Older adults (65 and over)
- Children under 5 (especially those under 2)
- Pregnant people and those within two weeks of giving birth
- People with underlying conditions
※ Chronic lung diseases (asthma, emphysema), cardiovascular disease, liver disease, kidney disease, blood disorders, neurological disorders, and metabolic diseases such as diabetes - People receiving immunosuppressive treatment
- People with extreme obesity
- Residents of long-term care facilities
In Japan, people with cancer are also considered a high-risk group.
Healthy Young People Can Also Become Seriously Ill
Older adults and young children are among the high-risk groups, but even young, healthy people without underlying conditions can become seriously ill.
According to data presented by Dr. Ishida on patients hospitalized with influenza, most patients who became seriously ill and needed hospitalization were older adults, but about 10% were under 65 and had no underlying conditions. The data also showed that the mortality rate among hospitalized patients in their 40s was 9%.
You cannot assume you are safe just because you are young or have no chronic conditions. I felt that the frightening thing about influenza is that it is impossible to predict who will become seriously ill.
What Causes Severe Illness: “Secondary Bacterial Pneumonia” and the Domino Effect
Why can influenza be “deadly”? There are reportedly two main ways this can happen.
- The cilia in the airways are damaged
- Illnesses occur throughout the body, one after another, like falling dominoes
Cilia Are Damaged
The surface of our airways has brush-like structures called cilia, which protect us by expelling foreign matter and bacteria.
However, the influenza virus damages these ciliated cells and causes them to detach. Bacteria—most commonly pneumococcus—invade the exposed area where the protective function has been lost, causing severe “secondary bacterial pneumonia.”
The Whole Body Deteriorates Like a Row of Falling Dominoes
In older adults whose bodily functions have declined, the effects can spread throughout the body, not just cause pneumonia.
- Damage to the cardiovascular system
Blood becomes more prone to clotting, increasing the risk of heart attack tenfold and the risk of stroke eightfold - Worsening of chronic conditions
Worsening diabetes, exacerbation of heart failure, and more - Progression of frailty
Strength does not return, and the person may become bedridden or need care
What measures can be taken to prevent the condition from worsening?
The Three Pillars of Influenza Prevention
There are three measures we can take against this unpredictable threat.
- Take antiviral drugs as soon as possible, ideally within 48 hours of symptom onset
- Vaccines are important for preventing severe illness
- Infection control measures: masks, cough etiquette, and 20-second handwashing
Take Antiviral Drugs as Soon as Possible, Ideally Within 48 Hours of Symptom Onset
Japan has a healthcare system that enables early diagnosis and treatment of influenza.
The purpose of five types of medication, including Tamiflu, Inavir, and Xofluza, is to “reduce the amount of virus quickly.” This can not only ease symptoms but also lower the risk of complications such as pneumonia and increase the likelihood of limiting transmission to others.
The basic principle of influenza treatment is to seek medical care and begin treatment early.
Vaccines Are Important for Preventing Severe Illness
Some people may have caught influenza despite getting vaccinated.
Vaccine effectiveness ranges from about 20% to 60%, depending on how well the vaccine matches the strains circulating that year. Let’s consider an effectiveness rate of 60%, for example.
- Assumption
About 10% of the population catches influenza each year. - Without vaccination
Of 100 people, 10 will develop the illness. - With vaccination
Of those 10 people, the number who develop the illness falls to 4. - Result
The number of cases falls from 10 to 4, meaning six people were protected. Six out of the original 10 cases is 60%, so the vaccine has an “effectiveness rate of 60%.”
Looking at the whole group of 100, it means that six people did not catch the flu, so the effect may be hard to notice. The explanation was that the effect is difficult to see unless you look at populations of hundreds or tens of millions.
I also learned the following about vaccines.
- High-dose vaccine
A “high-dose influenza vaccine” containing four times the usual amount of antigen is expected to be introduced in Japan in fall 2026 for older adults (75 and over), who may have difficulty developing immunity. - Co-administration of pneumococcal vaccine
The pneumococcal vaccine was also recommended alongside the influenza vaccine. Pneumococcus commonly lives in the noses of healthy children. If an older adult with weakened immunity holds a beloved grandchild and comes into contact with their nasal discharge, for example, transmission is possible.
Data from the United States reportedly showed that after pneumococcal vaccination began for children, not only did the rate of pneumonia among children fall, but the rate among older adults also declined (an indirect effect).
Infection Control Measures: Masks, Cough Etiquette, and 20-Second Handwashing
Take steps to prevent infection.
- Masks
Droplets travel 1–2 meters when someone coughs.
Cloth masks can keep your own droplets from spreading, but are less effective at blocking droplets from others. For prevention, use a nonwoven mask. - Cough etiquette
Cover your mouth and nose with a tissue when coughing or sneezing. Throw the tissue away after use. If you do not have a tissue, cover your mouth with your sleeve, not your hand. If droplets get on your hands, wash them with soap or disinfect them with alcohol. Wear a mask if you have a cough. - Handwashing
Wash your hands for about “20 seconds.”
Twenty seconds is about how long it takes to sing the first verse of the children’s song “Moshi Moshi Kame yo” once. If you cannot wash your hands, alcohol-based sanitizer is also effective against contact transmission.
Questions and Answers from the Audience
The audience asked questions such as the following.
Q. What are the side effects of the vaccine?
A. They are mainly localized swelling and pain, and systemic reactions tend to be milder than with COVID-19 vaccines. Data also indicate that the high-dose vaccine scheduled for introduction next year has no major differences in side effects from existing vaccines.
Q. How often should pneumococcal and RSV vaccines be given?
A. Pneumococcal polysaccharide vaccines are generally given every five years, while another type, the conjugate vaccine, can be given as a single dose. The RSV vaccine is new and there is little data, but its effects are thought to last about three years.
A severe RSV infection can cause pneumonia and other complications.
Q. Is alcohol-based sanitizer effective?
A. It is effective against contact transmission (infection through the hands). However, trying to do everything perfectly is endless, so it is more practical to choose specific times to use it, such as when you get home, before meals, or after using the toilet.
After Hearing the Truth About the Scary Side of Influenza
After listening to the lecture, what stayed with me was that not only older adults and people with underlying conditions, but also people without underlying conditions, are at risk of becoming seriously ill.
I learned about the true danger of influenza: you cannot know who will become seriously ill. The information about influenza forecasts and vaccines was also interesting.
To sum up, the three pillars of influenza prevention are as follows.
- Antiviral drugs (ideally within 48 hours)
- Vaccines (effective at preventing severe illness)
- Infection control (masks, handwashing, and so on)
Some people may have continued taking infection-control measures since the COVID-19 pandemic, but this lecture reminded me to seek medical care and treatment early, and to take precautions so I do not infect others as well as myself.
Articles About Kurashiki Central Hospital
Public Lecture: Kurashiki Central Hospital Medical Gathering “The Truth About the ‘Scary Flu’” Information
| Name | Public Lecture: Kurashiki Central Hospital Medical Gathering “The Truth About the ‘Scary Flu’” |
|---|---|
| Date | December 4, 2025 |
| Location | 1-11-11 Tsurugata, Kurashiki City, Okayama Prefecture |
| Admission (tax included) | Free |
| Website | Kurashiki Central Hospital Preventive Medical Plaza |
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