Cold and flu symptoms
Colds and flus both infect organs in the respiratory tract, including the nose and throat. Both come with unpleasant symptoms like fever, cough and blocked nose. But the common cold and influenza differ in their severity and in the pattern of symptoms they produce.
The common cold tends to be less severe and is typically associated with runny nose, sneezing and sore throat. These symptoms are less common with influenza, a more serious infection which usually produces a dry cough, body ache and headaches.
Symptom Cold Flu
Severity Less severe More severe
Duration 7-10 days 10-14 days
Onset Gradual Sudden
Fever Uncommon or mild Common and moderate to severe
Body ache Uncommon and mild Common and severe
Fatigue Mild Severe
Cough Mild and may not begin until 4-5 days after other cold symptoms Dry and commonly severe
Runny or stuffy nose Common Uncommon
Sneezing Common Less common
Sore throat Common Less common
Diarrhoea and/or vomiting Uncommon Common in children
Appetite Reduced appetite Loss of appetite
Colds typically begin slowly with a feeling of tiredness, a runny nose and sneezing. The ears are often affected and feel blocked or as though they are popping. Muscle aches, sore throat, headaches and a mild fever may also be experienced. The severity of symptoms peaks 2-3 days after infection and lasts 7-10 days. However, some symptoms may persist for several weeks.
The most common way for people to become infected with cold viruses is by touching the eyes and nose with contaminated hands. Rhinoviruses can survive on hands and surfaces for several hours. The other route of infection is by inhaling aerosols containing infected virus particles released after an infected individual has sneezed or coughed.
A flu is a more severe infection. It develops suddenly and is associated with:
Chills and sweats;
Loss of appetite;
General feeling of weakness.
Congestion, sore throat and eye pain may also be experienced. Diarrhoea and vomiting are more common in children. The flu lasts much longer than a cold. In some cases, it may lead to serious complications such as pneumonia.
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Cold or flu: How to tell the difference
Because colds and flus have many common symptoms, distinguishing between them can be difficult. The most accurate way is through diagnostic testing in the first few days of illness. However, the severity and type of symptoms are good indicators which can differentiate between colds and flus. Flus are generally more severe and typically involve systemic symptoms like body ache and fever.
Symptoms of the common cold generally improve without treatment. Influenza usually resolves with simple medicines like painkillers to treat symptoms, and does not generally require prescription medicines.
However, sometimes influenza symptoms persist and the infection causes serious complications which require treatment, including pneumonia. So it is important to be able to identify whether you have the common cold or influenza.
When is a cold or flu contagious?
Symptoms are the first sign of cold or flu infection and they typically begin 24 hours after the cold or flu germs have entered a person’s respiratory tract. But you are contagious and can pass the virus onto someone else as soon as you are infected. That means every time somebody gets the flu or a cold, they are contagious for about a day before they start to feel sick. That’s why it’s important to pay attention to cold and flu prevention measures like washing hands at all times, not just when someone in the house or office is sick.
Colds and flus remain contagious for about a week after infection occurs. The potential to transmit a cold to someone reduces after the second or third day of infection, but it is still possible to infect another person up to seven days later. If you have the flu, the risk of infecting someone else reduces after the fifth day.
For more information on preventing colds and flus, see Cold and Flu Prevention.
Common cold and flu: What causes these infections?
The common cold and flu are widespread infections of the upper respiratory tract caused by viruses. There are over 200 viruses that can cause colds. The most common one is the rhinovirus, followed by the corona virus and the respiratory syncytial virus. The large number of viruses capable of causing colds explains why we repeatedly catch colds.
Influenza or the flu is caused by the influenza virus, of which there are three major types – A, B and C. This virus is able to mutate and change its structure, giving rise to different strains every year. The body does not have any immunity to the new strain, so can be repeatedly infected. This is why you need to get a new flu vaccine every year.
Colds and flus are highly contagious. They can be passed from person to person by inhaling infected air droplets created from sneezing or coughing, or by hand contact or contact with surfaces that may have been touched by an infected individual (e.g. door knobs, pens and phones).
Colds and flus are usually not serious unless you develop complications. Some complications that may develop in high risk individuals include ear infections, pneumococcal pneumonia, sinusitis and bronchitis. Pneumonia is the most common and serious complication. It can be fatal for older people, or people with chronic illnesses. A generally healthy person is less likely to catch a cold or flu and if they do catch one, they will be better able to fight it.