Respiratory syncytial virus (RSV) affects the lung and airways, and is the most common cause of bronchiolitis and pneumonia in children under 1 year of age in the United States; RSV is the main cause of hospitalization in this age group. Infants infected with RSV during childhood are thought to be more likely to develop childhood asthma or wheezing. Almost all children are infected with RSV before the age of two. There is no vaccine against RSV, and treatment of active infection in children is supportive only i.e. there is no specific antiviral treatment available. Because the body's immune system does not build up protective immunity against RSV infection, and because there is no vaccine, repeated infection with RSV occurs through childhood and adult life. People with poor immune systems, those aged 65 years or more, and those with chronic lung or airway disease are particularly at risk if they suffer RSV infection.
Influenza, commonly known as "flu", is a highly infectious respiratory disease caused by any one of a number of influenza viruses. Infection can lead to an illness ranging in severity from mild to moderate to severe; complicated or severe influenza may lead to death. Common symptoms include fever, cough, sore throat, runny or stuffy nose, muscle and body ache, headache, and fatigue; children may also exhibit vomiting and diarrhea. Neurological complications are also well described.
According to the World Health Organization (WHO), influenza occurs worldwide, with an estimated annual incidence of 5% to 10% in adults and 20% to 30% in children. Influenza can lead to hospitalization and death, especially in high-risk groups (younger patients, geriatric patients, and those with chronic disease). Estimates are that influenza causes 3 to 5 million serious illnesses per year, and as many as 500,000 deaths.
Each year in the United States, approximately 36,000 deaths are directly attributed to influenza, and the virus hospitalizes more than 200,000 people.
Hepatitis B is a disease of the liver. It is caused when the hepatitis B virus (HBV) infects the liver.
Hepatitis B is transmitted when blood, semen, or other body fluids from an infected person enters the body of an uninfected person. This may happen through sexual contact, the sharing of needles, syringes, other drug-injection equipment, or from mother-to-baby transmission during childbirth. HBV causes both acute and chronic infections. The risk of developing chronic infection is related to one’s age at infection: approximately 90% of infected infants become chronically infected, compared with 2%–6% of adults. Chronic Hepatitis B can have serious complications, leading to cirrhosis of the liver, liver cancer, and death.
An estimated 240 million people suffer from chronic hepatitis B, while more than 780 000 people die each year from hepatitis B.