The flu vs. a severe cold – how to tell the difference


Now is the peak season for colds and influenza, and sometimes it's challenging to distinguish between the two because the symptoms of both illnesses can feel similar. Here, you'll learn the differences between influenza and cold symptoms.

A brief overview of influenza

Influenza has a relatively short incubation period, usually ranging from 1 to 4 days. This means that a person exposed to the influenza virus can develop symptoms within this timeframe. Once influenza has set in, the illness typically lasts for 7 to 10 days, with the most troublesome symptoms occurring during 3 to 5 days of that period, usually with fever, muscle aches, and a general feeling of illness.

However, sometimes it can be challenging to determine whether you've contracted influenza or just a severe cold that won't go away. Here are some differences:

  • Sudden onset and severity: Influenza tends to start suddenly and severely. You can wake up one morning feeling relatively fine, but then quickly deteriorate with fever, muscle aches, headache, and exhaustion. Colds tend to develop gradually, and the symptoms are usually milder.
  • Fever: Fever is usually higher and more prominent in influenza than in a cold. If your body temperature is 38°C (100.4°F) or higher, along with other flu symptoms, it's more likely to be influenza.
  • Muscle aches: Influenza is known for causing severe muscle aches and pain throughout the body. Colds typically cause milder aches.
  • Headache: Severe headache is more common with influenza than with colds.
  • Dry cough: Coughing is common in both influenza and colds, but it can be more pronounced and dry in influenza.
  • Sore throat: Influenza can also cause a sore throat, but it's usually milder than with a cold.
  • Stomach issues: Nausea, vomiting, and diarrhea are uncommon with influenza but can occur with some influenza strains. Colds typically do not affect the stomach in this way.
  • Duration: Influenza often lasts for a shorter period than a severe cold. Colds can persist for several days to a week or longer, while influenza usually lasts 7 to 10 days.
  • Seasonal variation: Influenza is more common during the winter months and often follows seasonal patterns. Colds, on the other hand, can occur at any time of the year.

What is influenza?

Influenza, also known as "the flu," is a viral illness that affects the respiratory system. It is caused by influenza viruses and is characterized by symptoms such as fever, muscle aches, headache, cough, runny nose, sore throat, and a general feeling of illness. Influenza can be severe and lead to complications, especially in individuals with weakened immune systems, the elderly, and young children.

How long does influenza last?

Influenza illness typically lasts for 7 to 10 days, although some symptoms like fatigue and cough may persist for several weeks after the initial influenza infection.

How does influenza spread?

Influenza primarily spreads through droplet transmission. This means that when an infected person coughs, sneezes, or talks, small virus particles can be released into the air and inhaled by others in close proximity to the infected person. Influenza viruses can also be transmitted through direct contact, such as handshakes, or by touching objects or surfaces contaminated with the virus and then touching the face, particularly the eyes, nose, or mouth. Therefore, it's important to practice good hand hygiene and cover your mouth and nose when coughing or sneezing to reduce the risk of transmission. Influenza vaccination is also an effective way to reduce the risk of getting sick and spreading the flu to others. Learn more about how to reduce the risk of getting infected and prevent the spread of influenza here.

How long is influenza contagious?

Influenza is contagious and can be spread to others from the day before symptoms begin and up to 5-7 days after you become ill. Contagiousness is usually highest during the first few days of the illness, but as long as you have a fever due to influenza, you can still transmit it to others.

Influenza usually resolves on its own, and most people do not need medical attention. If you are unsure whether you have influenza, it is best to contact healthcare professionals for assistance in confirming the influenza diagnosis and receiving advice on appropriate treatment. Regardless of the diagnosis, getting plenty of rest, staying hydrated, and avoiding spreading the illness to others when you are sick is essential.

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