COVID-19, the flu, a cold or allergies: What’s the difference in symptoms?

COVID-19, influenza, colds and allergies all affect the respiratory system, but in different ways.

It’s the time of the year when it seems our respiratory systems are under attack from all sides. We’re entering allergy season, when flowers and their pollen are in bloom. And while waning, it’s still cold and flu season. Now COVID-19 has entered the mix. These respiratory conditions are not only sharing boxes on the calendar; they also share some common symptoms.

It’s important for cancer patients especially to recognize and monitor symptoms and contact a doctor if they worsen or if the patient may have been in contact with someone who’s been sick.

So how do they know which condition they have? It’s a very important question, but we don’t have an easy answer at this time,” says Mashiul Chowdhury, MD, Infectious Disease Program Director for Cancer Treatment Centers of America® (CTCA). “Patients’ symptoms need to be evaluated very carefully.”

What’s the difference?

COVID-19, influenza, colds and allergies all affect the respiratory system, but in different ways. The U.S. Centers for Disease Control and Prevention (CDC) continues to update the list of symptoms COVID-19 patients may experience. Its latest update says common symptoms of the infection include a cough and shortness of breath or at least two of the following:

  • Fever
  • Chills
  • Repeated shaking with chills
  • Muscle pain
  • Headache
  • Sore throat
  • New loss of taste or smell

The most common symptoms for the other conditions include:

  • Influenza: Fever, cough, fatigue
  • Cold: Cough, sneezing, sore throat, runny nose
  • Allergies: Itchy and runny nose, swollen and watery eyes, sneezing

Influenza, COVID-19 and colds are caused by viruses. The flu and COVID-19 may be life threatening, but colds rarely are. Neither are allergies, which are caused by exposure and reaction to specific substances, or allergens, such as dust, dander or pollen. Allergy symptoms may last for weeks, depending on treatment or continued exposure. So how do you know which ailment you have? It may help to understand some key differences between these respiratory conditions:

  • Patients with common colds or allergies don’t usually develop a fever.
  • The incubation period for the flu is one to four days, for COVID-19 it’s two to 14 days.
  • Severe symptoms of influenza may develop and abate quickly, while COVID-19 symptoms may develop more gradually. Severe COVID-19 symptoms may not appear for several days after exposure.

“To help determine if a patient has COVID-19 requires asking a lot of questions,” Dr. Chowdhury says. “Geography is very important. We have a lot of hot spots in the United States and around the world. So, we’re asking where patients are from, where they’ve been and whether they know if they’ve been in contact with patients who’ve been exposed to the virus.”

COVID-19, cold, flu and allergy symptoms may cause severe complications for cancer patients, especially those with lung cancer or some head and neck cancers, like throat or sinus cancer, Dr. Chowdhury says. Even more confusing for some patients is that respiratory illnesses also share common symptoms with some cancers. Fever, coughing and difficulty breathing may be early signs of lung cancer, some forms of lymphoma or other cancers. For instance, a Florida woman battling flu-like symptoms for weeks learned later they were brought on by thyroid cancer.

Dr. Chowdhury recommends that patients with a fever call their doctor if it persists. “Some people may not have a fever, but they may have body aches, cough or sore throat, or maybe a loss of taste,” he says. “If you have a combination of symptoms, I would definitely call a doctor.”

Learn how COVID-19 may cause severe symptoms in lung cancer patients.