Viral disease

Polio is a viral disease that can infect the nervous system and cause paralysis. Most infections are mild, but a small number can lead to permanent disability.

Hepatitis B is a viral infection that attacks the liver and can become chronic. Chronic infection increases the risk of cirrhosis and liver cancer.

Hepatitis A is a viral liver infection usually spread through contaminated food, water, or close contact. It does not usually become chronic, unlike hepatitis B and C.

Zika is a mosquito-borne viral infection that is often mild in adults but can seriously harm a developing fetus. Infection during pregnancy can cause congenital Zika syndrome.

COVID-19 is a respiratory illness caused by the SARS-CoV-2 coronavirus. It ranges from mild infection to severe pneumonia, blood clots, and long-term health problems.