Imagine the morning: yesterday you felt fine, but today you woke up with a high fever, aches all over your body, and the feeling that a tram ran over you. That "ran over" feeling is almost always about flu, not a cold. So let's calmly sort out what this illness is, how it differs from an ordinary runny nose, and what to watch out for.
What flu is and why it is seasonal
Flu is an acute respiratory infection caused by influenza viruses. According to WHO, about one billion cases of seasonal flu are registered worldwide each year, including 3–5 million cases of severe illness and 290,000 to 650,000 respiratory deaths. The numbers sound alarming, but most people recover on their own.
Seasonal epidemics are caused by influenza viruses of types A and B. In temperate climates they occur mainly in winter, while in the tropics the illness occurs year-round. Flu spreads easily — through droplets from coughing and sneezing, as well as through contaminated hands. The incubation period is short: symptoms usually appear 1–4 days after infection.
Flu is a seasonal viral infection that spreads quickly, but most adults get through it at home.
Abrupt onset, fever, aches: how to tell it from a cold
Here is where the main practical difference lies. A cold creeps up gradually, over a day or two, and mostly affects the nose and throat — you feel unwell but can work. Flu appears very quickly, within a few hours, and affects not only the nose and throat: you feel exhausted and far too unwell to go about your usual activities.
Typical signs of flu:
- sudden high fever and body aches;
- dry cough and sore throat;
- headache, fatigue, and exhaustion;
- poor sleep and loss of appetite.
In children the picture is similar, but ear pain, eye pain or irritation, enlarged glands, and noticeable lethargy may be added. A cough sometimes lasts two weeks or longer.
If the illness knocked you off your feet within a few hours and your whole body aches — think flu, not a cold.
Who is at increased risk
Flu itself can cause severe illness and death, especially in people in risk groups. In severe cases it leads to pneumonia and sepsis, and also worsens chronic diseases. WHO classifies pregnant women, children under 5, older people, people with chronic diseases of the heart, lungs, kidneys, liver, metabolism, or nervous system, as well as people with weakened immunity, as groups at increased risk of severe illness.
Healthcare workers are also at increased risk — both of becoming infected and of passing the virus to vulnerable patients. If you belong to one of these groups, pay closer attention to symptoms and do not delay seeing a doctor. If you are an adult without chronic diseases, most likely everything will pass within a week.
The risk of complications is determined not by strength of character but by age, pregnancy, and chronic diseases.
Vaccination as prevention
WHO directly calls vaccination the best way to prevent flu. The vaccine helps protect against flu, and it is offered every year in autumn or early winter to people at increased risk. Vaccination also protects healthcare workers and the people around them.
Cover your mouth and nose with a tissue when coughing, wash your hands regularly, and stay home when you have a high fever so as not to infect others. Antibiotics do not work on the flu virus, so do not ask your doctor for them.
Vaccination and basic hygiene are the most reliable practical protection.
When to see a doctor
Most cases of flu are diagnosed clinically, based on symptoms. In more complex situations, the doctor may refer you for laboratory testing to confirm the virus. People in risk groups or with severe symptoms need medical care as soon as possible — not because you are "weak," but because time matters. Why does the doctor ask whether you are pregnant or have a heart condition? Because these are the groups that most often need closer monitoring.
Seek urgent medical help if you or your child belong to risk groups, if you feel very unwell, if shortness of breath appears, or if symptoms do not go away within seven days. And there are signs with which you do not wait at all.
Call an ambulance (103 or 112) or go to the emergency department if sudden chest pain appears, if breathing is very severe (the person gasps for air, is short of breath, cannot say words), or if there is a cough with blood. Do not drive yourself — ask someone to take you or call an ambulance.
Warning signs are a reason not to "wait it out" but to seek medical help immediately.
This material is for reference and does not replace a doctor's consultation — make decisions about examination and care together with your doctor.
Sources
Update history
This content is for reference and does not replace a doctor's consultation. Medical disclaimer