COVID-19 is an illness caused by a respiratory virus that produces a range of symptoms, from very mild to severe. A temporary increase in body temperature, commonly known as a fever, is frequently one of the first signs that a person has become infected with the virus.
Defining a COVID-19 Fever
A body temperature of 100.4°F (38°C) or higher is generally accepted as the threshold for a fever in adults. This number represents an average above the typical range, as a person’s normal body temperature can fluctuate throughout the day. Not every person infected with COVID-19 will develop a fever, as some may experience only a low-grade temperature or no fever at all.
Using a digital thermometer to take an oral temperature is generally considered the most dependable method for adults to reliably track the symptom’s course. For the most consistent reading, avoid measuring immediately after consuming hot or cold drinks. Wait at least 30 minutes after taking any fever-reducing medication before checking the temperature.
Typical Duration and Progression of Fever
The duration of a fever associated with a COVID-19 infection varies significantly among individuals, depending on factors such as vaccination status and the overall severity of the illness. For many people experiencing a mild-to-moderate case, the fever often resolves within five to seven days of symptom onset. In some earlier studies focusing on more severe cases, the average duration of fever was reported to be around twelve days for those who recovered.
The fever is frequently the first symptom to appear, often preceding the development of a cough or shortness of breath by a few days. The intensity of symptoms, including the fever, may peak sometime around day four through day seven of the illness. In milder cases, a person may notice the fever is intermittent, meaning the temperature rises and falls throughout the day.
Studies have indicated that fever is a common, but not universal, symptom of the infection. Approximately 78-79% of adults with COVID-19 have been observed to run a fever at some point during their illness. For those who experience a more prolonged illness, the fever may plateau or gradually begin to resolve after the first week.
For individuals whose symptoms remain mild, a marked improvement, including the reduction of fever, is often seen around two weeks after the first symptoms appeared. Those with more severe illness may experience symptoms, including fever, that last for up to six weeks or longer.
Warning Signs Related to Prolonged or High Fever
While a fever is a normal sign of the body fighting an infection, certain temperature levels or durations signal the need for medical attention. Adults should contact a healthcare provider if their temperature reaches 103°F (39.4°C) or higher. Such a high temperature can indicate a more serious infection or a complication that requires professional assessment.
A persistent fever that lasts beyond five to seven days is also considered a red flag that warrants a consultation with a doctor. If a fever does not break or continues to rise over multiple days, it suggests the infection is not resolving as expected in a typical mild case. Monitoring the temperature regularly helps track this progression and provides concrete data for a healthcare provider.
The fever combined with other specific symptoms may be a sign of a severe illness requiring immediate emergency care. These urgent signs include:
- Difficulty breathing or shortness of breath
- Persistent pain or pressure in the chest
- New confusion
- Inability to wake or stay awake
- Pale, gray, or blue-colored lips, face, or nail beds
Monitoring these signs is particularly important for individuals who have underlying health conditions or who are otherwise at a higher risk for severe outcomes.