Viral infections are the most common cause of illness in children. They are highly contagious. Most viruses cause symptoms over a short period of time and produce mild illness. Some viruses can cause significant disease, especially in those who have chronic or debilitating conditions.

Respiratory Viruses

Respiratory viruses affect children by causing ear and throat infections, cough, runny nose and difficulty breathing. Some of these viruses can cause wheezing, pneumonia and respiratory failure. The most common respiratory viruses are the influenza virus, respiratory syncytial virus (RSV), rhinovirus and adenovirus. The Epstein-Barr virus causes mononucleosis, a common upper respiratory infection characterized by enlargement of neck glands and swelling of the throat.

Gastrointestinal Viruses

Gastrointestinal viruses cause vomiting and diarrhea. These symptoms can lead to dehydration. Common gastrointestinal viruses are rotavirus, enterovirus and the cholera virus. Other gastrointestinal viruses include those responsible for liver disease, including the hepatitis viruses, cytomegalovirus and the Ebstein-Barr virus.

Central Nervous System Viruses

These viruses penetrate the central nervous system, including the brain and the spinal cord, and cause meningitis, which is an inflammation of the tissues surrounding the brain, and encephalitis, an infection of the brain. The most common viral causes of meningo-encephalitis are enteroviruses, arboviruses (the most recognized arbovirus is the West Nile virus), and the herpes virus. Herpes can cause a devastating disease, usually presenting with seizures. In newborns, it can lead to permanent brain damage. The rabies virus also penetrates the brain, where it induces encephalitis. The HIV virus causes significant central nervous system disability.

Vaccines Against Viruses

Advances in medicine have lead to the development of several vaccines that protect against viruses which once caused disease. Among these are the measles, mumps and rubella vaccine, the varicella vaccine (which protects against the virus that causes chickenpox), the hepatitis A and B vaccines, the influenza vaccine and the rotavirus vaccine. Other medicines act to prevent significant damage by these viruses. For example, Acyclovir is an antiviral that acts against the herpes virus. There is a vaccine against the rabies virus, but it is only used when there is suspicion of an exposure to rabid animals.