Updated July 2025

When you're feeling under the weather, it can be hard to determine the cause of your symptoms, especially during the colder parts of the year when several virus types – the common cold, influenza, COVID-19 and RSV (respiratory syncytial virus) – are circulating. Fortunately, most respiratory infections are mild and manageable at home with rest, hydration and over-the-counter medications.

Emergency medicine specialist Dr. Jahan Fahimi and infectious disease specialist Dr. Peter Chin-Hong share which symptoms to watch for, when to test and how to avoid spreading illness to others.

Note: If you're experiencing severe symptoms – such as difficulty breathing, chest pain or confusion – seek medical care immediately or call 911.

Is it possible to tell the difference between cold, flu and COVID-19 symptoms?

"It can be difficult because there’s so much symptom overlap," says Fahimi. Common symptoms of respiratory viruses include:

  • Fever, chills and body aches
  • Cough, sore throat and runny nose
  • Fatigue
  • Headache

Less common symptoms of respiratory viruses include digestive upset, such as nausea or diarrhea.

Because respiratory illnesses share similar symptoms, the best way to determine which one you have is to take a test at home.

"You really can't rely on symptoms alone to tell the difference," Chin-Hong says. "At this point, rapid home testing is the easiest way to get clarity."

What should I do if I feel sick?

If you’re feeling unwell:

  • Stay home and rest.
  • Avoid close contact with others, especially those at high risk for severe illness.
  • Wear a mask if you must be around others.
  • Wash your hands frequently.
  • Consider using at-home kits to test for COVID-19, the flu or both.

Testing can guide your next steps, including choosing treatments and protecting others. Flu and COVID-19 combination test kits are now widely available.

"If you're high-risk [for becoming severely ill] due to older age, being immunocompromised or having a chronic condition, talk to your doctor early," Chin-Hong says. "Treatments like Paxlovid for COVID-19 or Tamiflu for the flu are most effective when started quickly."

What if I test negative but still feel sick?

Even if your COVID-19 and flu tests are negative, it's best to continue taking precautions until your symptoms resolve. Other viruses – such as the common cold and RSV – are also circulating.

"You don't have to stress too much about identifying the exact virus," Fahimi says. "Focus on not spreading it and taking care of yourself."

When should I seek medical attention?

Seek immediate care if you have:

  • Difficulty breathing
  • Chest pain or pressure
  • Sudden confusion
  • Severe fatigue or dehydration

If your age or other factors put you at risk for getting seriously sick, reach out to your provider promptly. Starting treatment right away can help prevent complications.

How do these viruses spread and how can I protect others?

"Respiratory viruses spread through droplets and aerosols released when we talk, sneeze or cough," Fahimi says. "Some, like COVID-19, can be spread even before symptoms appear."

To reduce the spread of illness:

  • Wash your hands regularly.
  • If you're feeling sick, stay home.
  • Keep your immune system strong by embracing healthy sleep, exercise and eating habits.
  • Stay up-to-date on your flu and COVID-19 vaccinations.
  • If you're at high risk of severe illness wear a mask in poorly ventilated or crowded spaces when transmission rates are high.