A fever represents a temporary elevation in the body’s temperature. Normal body temperature typically ranges from 97.5°F to 98.9°F (36.4°C to 37.2°C), with a fever generally considered to be 100.4°F (38°C) or higher. A fever is a symptom, not an illness itself.
Fever as a Symptom
A fever is a response by the body’s immune system to combat threats, such as infections. When pathogens like viruses or bacteria invade, the immune system releases chemical messengers called pyrogens. These pyrogens travel to the hypothalamus, prompting it to raise the body’s core temperature. This elevated temperature creates an environment less favorable for pathogen growth and replication.
Raising the body’s temperature enhances the efficiency of immune cells, like white blood cells. This speeds up the healing process by boosting the immune response. While infections are the most frequent cause, fevers can also result from non-infectious conditions such as inflammation, autoimmune diseases, certain medications, or heatstroke. The underlying infection or condition might be transmissible, not the fever itself.
Common Fever-Causing Illnesses and Their Spread
Illnesses that cause fever spread through various mechanisms, involving the transfer of infectious agents like viruses and bacteria. Respiratory infections, such as the common cold and influenza, are frequently accompanied by fever. These viruses primarily spread through respiratory droplets expelled when an infected person coughs, sneezes, talks, or laughs. These droplets can then be inhaled by others or land on surfaces.
The common cold, often caused by rhinoviruses, is highly contagious and spreads through direct contact, such as shaking hands with an infected individual, or by touching contaminated surfaces and then touching one’s eyes, nose, or mouth. Influenza viruses spread similarly, through droplets and contact with contaminated objects. People can be contagious with the flu even before symptoms appear and for several days after becoming sick. Strep throat, a bacterial infection, is also highly contagious and spreads through respiratory droplets, as well as direct contact or shared items.
Gastrointestinal illnesses, often referred to as “stomach bugs,” can also cause fever and are spread through the fecal-oral route. This occurs when microscopic particles of feces from an infected person are ingested by another. Norovirus, a common cause of severe vomiting and diarrhea, spreads easily through contaminated food or water, direct contact with an infected person, or by touching contaminated surfaces. Viruses like norovirus can be shed in stool for days or weeks after symptoms have subsided. This transmission route is linked to inadequate hand hygiene after using the restroom or handling contaminated food.
Minimizing Illness Transmission
To reduce the risk of contracting and spreading fever-causing illnesses, practicing good hygiene is essential. Regular handwashing with soap and water for at least 20 seconds is a primary defense, especially after coughing, sneezing, using the restroom, and before eating or preparing food. If soap and water are unavailable, an alcohol-based hand sanitizer with at least 60% alcohol can be used, though it is less effective against some viruses like norovirus.
Covering coughs and sneezes with a tissue or into the elbow, rather than the hands, helps contain infectious droplets. Avoiding touching the face, particularly the eyes, nose, and mouth, prevents germs from entering the body. Regularly cleaning and disinfecting frequently touched surfaces, such as doorknobs, light switches, and phones, reduces the presence of pathogens. Staying home when sick, especially with fever, is crucial to prevent transmitting illness to others, including vulnerable populations. Vaccination also prevents specific diseases, like influenza, by preparing the immune system to recognize and fight off pathogens before severe illness develops.