Is 99.0 a fever?

Understanding Fever

A fever is commonly an indication of an underlying illness or infection, like COVID-19. Generally, health professionals define a fever in adults as a body temperature ranging from 100 to 100.4 degrees Fahrenheit. In the case of infants and children, a fever is identified with an oral temperature of 99.5 degrees Fahrenheit or a rectal temperature of 100.4 degrees Fahrenheit.