Influenza B virus in the context of "Influenza viruses"

Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four (typically two) days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.

There are four types of influenza virus: types A, B, C, and D. Aquatic birds are the primary source of influenza A virus (IAV), which is also widespread in various mammals, including humans and pigs. Influenza B virus (IBV) and influenza C virus (ICV) primarily infect humans, and influenza D virus (IDV) is found in cattle and pigs. Influenza A virus and influenza B virus circulate in humans and cause seasonal epidemics, and influenza C virus causes a mild infection, primarily in children. Influenza D virus can infect humans but is not known to cause illness. In humans, influenza viruses are primarily transmitted through respiratory droplets from coughing and sneezing. Transmission through aerosols and surfaces contaminated by the virus also occur.

Oseltamivir, sold under the brand name Tamiflu among others, is an antiviral medication used to treat and prevent influenza A and influenza B, viruses that cause the flu. Many medical organizations recommend it in people who have complications or are at high risk of complications within 48 hours of first symptoms of infection. They recommend it to prevent infection in those at high risk, but not the general population. The Centers for Disease Control and Prevention (CDC) recommends that clinicians use their discretion to treat those at lower risk who present within 48 hours of first symptoms of infection. It is taken by mouth, either as a pill or liquid.

Recommendations regarding oseltamivir are controversial as are criticisms of the recommendations. A 2014 Cochrane Review concluded that oseltamivir does not reduce hospitalizations, and that there is no evidence of reduction in complications of influenza. Two meta-analyses have concluded that benefits in those who are otherwise healthy do not outweigh its risks. They also found little evidence regarding whether treatment changes the risk of hospitalization or death in high risk populations. However, another meta-analysis found that oseltamivir was effective for prevention of influenza at the individual and household levels.