Flu Symptom Checker

The flu is infamous for its array of symptoms, including body aches, coughing, and fever. But what exactly triggers such discomfort? Explore the reasons behind your symptoms below.

Fever

When viruses invade, they prompt the release of pyrogens into the bloodstream. These substances activate cold-sensing neurons in the hypothalamus, the body's temperature regulator. In response, the hypothalamus increases body temperature, boosting the activity of white blood cells that combat infections and slowing the growth of heat-sensitive viruses.

Headache

When the body's inflammatory reaction to the virus begins, the arteries in the head widen, aggravating nearby nerve endings within the skull. As fever intensifies, the heart rate increases, pushing more blood through the body, including the head, leading to a throbbing headache.

Sore Eyes

The mucous membranes in the eyes and nose are linked, and both become inflamed during an infection. Blood vessels in the eyes often expand, resulting in redness, a burning sensation, and heightened sensitivity to light.

Nasal Congestion

Nasal congestion occurs when blood vessels in the mucous membranes swell, filling the area with fluids and white blood cells that combat the virus. This leads to a blocked or runny nose.

Cough

Irritation in the respiratory tract and mucus drainage from the nasal passages can provoke the cough reflex. A "dry" cough, which doesn't produce phlegm, is typical in flu cases. However, a "productive" cough might indicate a secondary infection like bronchitis or pneumonia.

Sore Throat

The sore throat and trouble swallowing result from inflamed throat tissues as the virus invades the upper respiratory tract.

Fatigue

Flu-related fatigue stems from the body channeling energy into fighting the virus and the impact of immune-response signaling cells on the nervous system.

Body Aches

As the virus progresses, white blood cells battle for control, and immune-response messengers affect muscle cells, leading to widespread body aches.