Colds vs Flu
Two viruses, two very different weeks. How to tell a common cold from the flu using the CDC symptom chart, how long each usually lasts, and the warning signs that need care.
Influenza viruses under an electron microscope: CDC / Cynthia Goldsmith, Public domain
Same sniffles, different viruses
A cold is a viral infection of the upper airways. The CDC says more than 200 respiratory viruses can cause colds, with rhinoviruses the most frequent cause in the United States. Colds usually last less than a week, and US adults catch an average of two to three a year, while children often get more.
Flu is caused by influenza viruses. The CDC describes it as a contagious respiratory illness that can be mild or severe and at times can lead to death. Most people recover in a few days to less than two weeks, but some develop complications such as pneumonia.
Spotting the difference
The biggest clue is speed. In the CDC's comparison chart, cold symptoms start gradually while flu starts abruptly. Fever is rare with a cold but common with flu, often lasting 3 to 4 days. Aches are slight with a cold and often severe with flu. Sneezing, a stuffy nose and a sore throat are common with colds, while tiredness, headache and chills are more typical of flu.
The NHS puts it in everyday terms: a cold mainly affects your nose and throat and still lets you get on with your day, while flu tends to leave you exhausted and too unwell to carry on as normal. Not everyone with flu has a fever, the CDC notes.
Who is at higher risk
Anyone can get very sick with flu. The CDC says people at higher risk of serious complications include adults 65 and older, people with certain long-term conditions such as asthma, diabetes or heart disease, pregnant women, and children younger than 5, especially those under 2. If you are in one of these groups and get flu-like symptoms, contact a licensed healthcare provider early, because the CDC notes that some treatments work best when started soon after symptoms begin. Antibiotics do not work on viral infections such as flu, the NHS explains.
Prevention and warning signs
The CDC recommends a flu vaccine every season for everyone 6 months and older, with rare exceptions. Washing hands well also helps stop the spread of respiratory germs.
Get medical care right away for emergency warning signs. For children, the CDC lists fast or troubled breathing, bluish lips or face, ribs pulling in with each breath, chest pain and signs of dehydration, among others. For anyone, trouble breathing, ongoing chest pain or pressure, or sudden confusion are reasons to seek emergency care or call 911.
Facts on this page were checked against these sources.
- Influenza viruses under an electron microscope: CDC / Cynthia Goldsmith, Public domain
- A rhinovirus model: Thomas Splettstoesser (www.scistyle.com), CC BY-SA 4.0
Text written by Microscopic Doctor.
