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Got a Fever? Find Out What It May Mean

Dr. Erik L. Larsen, Emergency Medicine

January 12, 2021

Got a Fever? Find Out What It May Mean

After COVID-19 has been ruled out, here are some other reasons you could be running a little warm.  

In our heightened state of alert during this pandemic, fevers are not something to be taken lightly—especially when paired with other symptoms consistent with COVID-19, such as body aches, fatigue, cough and sore throat. If you have any of these symptoms and think you may have been exposed, you should immediately arrange to get a COVID-19 test, says Dr. Erik Larsen, Assistant Director of EMS & Emergency Preparedness at White Plains Hospital.

However, COVID-19 may not be the only reason your thermometer is spiking above 98.6.
“Fevers are often misunderstood; fever may be a sign that your body is fighting an infection,” adds Dr. Larsen. “But in our current climate the best course of action is to seek medical attention so you can determine the cause as soon as possible and take the proper steps to isolate or get treatment.”

Dr. Larsen goes to the source of some common causes of fevers:


Many people who test positive for COVID-19 experience mild fevers and side effects for a short period of time but recover fine at home. However, if you recently tested positive for COVID and were asymptomatic, but now have worsening symptoms, Dr. Larsen provides some reasons to seek immediate care in the Emergency Department.

  • Fever greater than 103 F
  • Respiratory rate greater than 24 times per minute (count how many breaths in 60 seconds).
  • Heart rate greater than 120 beats per minute (take your radial pulse in your wrist or your carotid pulse in your neck).

Additionally, people who fall into the follow categories and are known to be positive for COVID should seek immediate medical care for their fever:

  • Over 60 years old
  • Chronic illnesses, such as lung, kidney, congestive heart failure and coronary artery disease
  • Metabolic conditions such as obesity, diabetes and hypertension
  • Immunocompromised (HIV, cancer, chronic steroid use, immunosuppressant medications)
  • A blood relative that required critical care for COVID in the past

Other Viral infections 

Almost all viruses, including the ones that cause the common cold, pneumonia and bronchitis, can give you a fever. “Once these foreign bodies enter the bloodstream, they stimulate chemicals called pyrogens, which instruct the brain to turn up the body’s heat to make it more inhospitable to these potential threats,” says Dr. Larsen. “Heat makes white blood cells more effective killers, providing more energy to fight the virus.”

Viral infections can have symptoms like but not limited to sore throat, cough, headache, diarrhea and rash, which may come before or after the fever. The fever is the sign that the body’s immune system has been activated and it’s trying to get rid of the virus.

Bacterial infection

The body’s reaction to bacterial infections is similar as for viruses, but it can sometimes be more serious. Often the body can fight bacteria back, however antibiotics may be called on for additional help to fight other symptoms (antibiotics don’t work for viruses). “We also use antifungal drugs and anti-parasite drugs for diseases like malaria, which cause the body to experience a roller coaster of spiking fevers,” says Dr. Larsen.

Some immunizations

Vaccines to prevent a bacterial or viral infection prepare our bodies to come in contact with that infection later. So when you get the vaccine, your body’s immune response is stimulated and the body says, “Whoa, what is this?” It may then mount a fever. “When you get a vaccine, you’re not really exposed to an active infection, but it prepares your body for that sometime in the future when you may become exposed to that infection,” says Dr. Larsen. “This is true of the current COVID-19 vaccines now being administered.” Vaccines for diphtheria, tetanus, whooping cough (DTaP) and pneumonia have also been known to cause this reaction and spike a fever.

Dr. Erik L. Larsen

Erik Larsen MD, FACEP, is Assistant Director of EMS & Emergency Preparedness at White Plains Hospital. For less severe illnesses and injuries, the Hospital also offers its Urgent Care Center at White Plains Hospital Medical & Wellness in Armonk, located 10 minutes away from the Hospital. Call 914-849-7999.


Similar Topics: bacteria, Emergency, infection, virus,