In many parts of Korea, including Busan and Gyeongnam, respiratory illnesses like colds, flu, and COVID-19 are increasing together. As the big temperature gap during the seasonal change and the dry weather continue, concern about health care is also growing. Health authorities said this spread may continue for a while. The article especially highlighted the increase in rhinovirus. It said that, based on KDCA sentinel surveillance, the number of hospitalized rhinovirus patients rose from 132 in the first week of March to 424 in the second week of April. It is more accurate to read this number as reports from institutions taking part in sentinel surveillance, not as a national total of all confirmed cases. It explained that rhinovirus causes cold symptoms like runny nose and sore throat, and in severe cases it can lead to pneumonia. It also said that with spring pollen added on top, symptoms like coughing and sneezing can feel worse. Health authorities asked people to wear masks, wash hands, and manage personal hygiene well.
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Why this spring in Korea feels especially noisy right now
You might feel like, why does my body hurt like it is still midwinter even though it is spring? This spring is close to a picture where the tail of winter flu is still left, and on top of that rhinovirus, a main virus that causes the common cold, plus human coronavirus and metapneumovirus are overlapping at the same time. But here, coronavirus means a broader flow of respiratory viruses that includes other human coronaviruses found together in sentinel surveillance pathogen data, separate from the COVID-19 in the article.
If you look at Korea Disease Control and Prevention Agency surveillance data, this is not something completely sudden. In Korea's spring seasonal transition, several respiratory viruses could already spread together, but after the pandemic, the seasonal lines became less clear, so this overlap changed into something people feel for longer and in a more complex way. Simply put, before, it felt like 'winter flu ends and then spring cold comes,' but now it is closer to a relay where the next runner comes in before the first one finishes.
So when the news says colds, flu, and COVID are spreading at the same time, it is a bit too much to understand it as 'all three diseases exploded in exactly the same way.' More accurately, it is better to see it as waves of different virus outbreaks layering over the same time period. Understanding this helps explain why one person only gets a runny nose, while another person gets high fever and body aches all at once.
This spring outbreak is closer to an overlap of leftover winter spread and spring viruses, not a problem of one new virus.
After the pandemic, seasonality became less stable, so this kind of overlap can feel longer.
Flu indicators rose again in spring
Looking at the 2025 spring influenza-like illness rate, the number of suspected flu patients per 1,000 outpatients, the flu that seemed ready to fall started rising again.
Viruses that were spreading together in spring
| Category | Virus | Detection rate |
|---|---|---|
| Outpatient | Influenza | 17.2% |
| Outpatient | Rhinovirus | 13.7% |
| Outpatient | Human coronavirus | 12.1% |
| Hospitalized | Rhinovirus | 26.7% |
| Hospitalized | Metapneumovirus | 21.3% |
| Hospitalized | Human coronavirus | 16.9% |
How true is the saying, 'You get sick during the seasonal change'?
If you live in Korea for a long time, you hear people say a lot, 'If the day and night temperature gap is big, you always catch a cold.' This is not completely wrong, but if you understand it as the cold causes illness, then it is only half right. A cold happens because of a viral infection, and cold weather is closer to an environment that helps that infection happen more easily.
Research shows that cold air can weaken the local immunity of the nasal mucosa, the first defense barrier that works right inside the nose. Also, in dry air, viruses spread more easily, and when the day and night temperature gap is big, people stay indoors longer and ventilate less. So the key is not 'immunity suddenly drops all at once,' but the combination of cold air + dryness + crowded indoor spaces + poor ventilation.
This is not only a Korea story. In countries with temperate climates, a similar overlap appears from late winter to spring. But in Korea, after the pandemic, the seasonality of the flu and other respiratory viruses became less regular, so compared with before, 'seasonal change colds' now feel more complex.
Instead of saying, 'You catch a cold because it is cold,' it is more scientific to say, 'A cold and dry environment helps virus spread and weakens the defense of the nasal mucosa.'
How are a cold, the flu, and COVID different in the body?
| Category | Cold | Flu | COVID-19 |
|---|---|---|---|
| Main cause | Rhinovirus and others | Influenza virus | SARS-CoV-2 |
| How it starts | Starts slowly | Starts suddenly | Very different by person |
| Main symptoms | Runny nose, stuffy nose, sore throat | High fever, chills, muscle pain, tiredness | Cough, sore throat, fever, possible changes in smell and taste |
| Whole-body symptoms | Usually mild | Usually strong | Medium to strong, big difference |
| Pneumonia risk | Possible in high-risk groups | Be careful in high-risk groups | Need wider caution relatively |
| When testing is needed | Shortness of breath, chest pain, high-risk group | When early treatment is being considered | During an outbreak, for high-risk groups, or when severe illness is suspected |
Points to check at home first: is it a pollen allergy or a cold?
In spring, viruses are not the only problem. If a pollen allergy comes too, it can be really confusing.
How to read the numbers in the article
| Indicator | What is counted | How to read it |
|---|---|---|
| Number of hospitalized patients in sample surveillance | Patients reported by participating medical institutions | A number for seeing trends, not a full nationwide count |
| Influenza-like illness rate (ILI) | Number of suspected flu patients per 1,000 outpatients | A key indicator for seeing how much the flu has spread |
| Epidemic standard | Seasonal statistical baseline | Numbers like 8.6 people and 9.1 people can change every year |
| Pathogen detection rate | Virus rate confirmed by specimen PCR | It shows which viruses are spreading at the same time |
How has mask culture in Korea changed after COVID?
Behind the health authorities stressing masks and handwashing again now, there have been big changes over the past few years.
Stage 1: Before COVID
Masks were closer to an optional tool mainly used in specific situations like yellow dust, fine dust, flu season, and MERS.
Stage 2: 2020–2022
When COVID-19 came, masks, handwashing, and cough manners became a nationwide public norm. During this time, other respiratory infections like the flu were also greatly suppressed.
Stage 3: After 2023
As disease control measures were relaxed, the flu and many respiratory viruses that had been suppressed came back strongly. People also started to accept more naturally the culture of voluntarily wearing a mask when sick.
Stage 4: Now
Korea's response has moved from mandatory disease control to voluntary disease control. Legal duties have decreased, but wearing a mask when you have symptoms and taking care of hand hygiene have in effect become the new basic manners.
How the pandemic changed the ups and downs of flu outbreaks
If you look at the suspected patient rate based on the same week 23, it was suppressed during the pandemic and then jumped up again a lot after that.
So, what we should remember this spring
The key point this spring is not that 'strangely, everyone got weaker.' An environment where several viruses can spread at the same time was created, and after the pandemic even the seasonal pattern became unstable, so people feel it more strongly. So even if it looks like many people around you are sick, if you think it must be because of just one same illness, you may miss something.
In daily life, you do not need to think about it in a very complicated way. If fever and body aches are strong, keep open the possibility of flu or COVID, and if itching and repetition are strong, also suspect pollen allergy. If you are in a high-risk group or have shortness of breath and chest pain, treatment including testing should come first rather than 'let's endure a few more days.'
To say it a little more fun, spring respiratory illness in Korea is now no longer a simple 'cold season' like before, but closer to a mixed show where flu, cold, allergy, and COVID come onto the same stage. That is why people are again saying that basics like masks, handwashing, and ventilation are still the cheapest and surest defense.
People age 65 or older, infants and young children, pregnant women, immunocompromised people, and people with chronic diseases can get worse more quickly even if it looks like a cold.
If there is shortness of breath, chest pain, reduced consciousness, dehydration, or cyanosis, you should not pass it off as simple seasonal change symptoms.
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