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Which early symptoms can occur during a polio infection?

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Polio vaccine — polio A health care worker giving a polio vaccine to a child in Katsina state, Nigeria, 2014.

Polio, or poliomyelitis, is a contagious viral disease that often presents with mild or no symptoms in many cases. When symptoms do occur, the infection typically begins with a vague, flulike illness.12

The most common early symptoms of polio include:

Mild headache2
Fever12
Sore throat2
Nausea and vomiting2
Diarrhea2
Restlessness2
Drowsiness2

In these mild cases, the fever usually peaks within two to three days and then subsides, with patients typically recovering within three to four days without developing paralysis.2

However, if the virus invades the central nervous system, the clinical presentation can become more severe. Individuals at this stage often become irritable and may experience pain in the back and limbs, muscle tenderness, and a stiff neck. While many patients recover at this stage, some may progress to develop paralysis due to the destruction of motor neurons in the spinal cord and brainstem.21