From the Guidelines
Influenza A, also known as Influenza Type A, is a type of influenza virus that causes epidemic human disease in a seasonal pattern, further classified into subtypes based on surface antigens such as hemagglutinin and neuraminidase 1.
Key Characteristics of Influenza A
- Influenza A viruses are responsible for seasonal epidemics and can also cause pandemic influenza when antigenic shifts are more pronounced than usual 1.
- The virus is classified into subtypes based on two surface antigens: hemagglutinin and neuraminidase, and these subtypes can vary from year to year 1.
- Immunity to surface antigens protects individuals against infection and severe disease, but antibodies against one influenza virus type or subtype confer little or no immunity against other types and subtypes 1.
Transmission and Prevention
- Influenza A spreads through respiratory droplets, and good hand hygiene, avoiding close contact with sick individuals, and covering coughs and sneezes can help prevent transmission 1.
- Vaccination is the primary mode of prophylaxis against influenza, with the US Advisory Committee on Immunization Practices (ACIP) recommending annual influenza vaccination for high-risk individuals such as those 50 years of age and older, young children, pregnant women, and adults with chronic conditions 1.
Clinical Presentation and Complications
- Typical influenza illness is characterized by abrupt onset of fever, myalgia, sore throat, and nonproductive cough, with more severe illness resulting in primary influenza pneumonia or secondary bacterial pneumonia 1.
- Complications can include pneumonia, bronchitis, sinus infections, and ear infections, particularly in vulnerable populations such as the elderly, young children, and those with chronic health conditions 1.
From the Research
Definition of Influenza A
- Influenza A, also known as Influenza Type A, is a type of influenza virus that can cause illness in humans 2, 3, 4, 5, 6.
- It is one of the three main types of influenza viruses, along with Influenza B and Influenza C 3, 4.
Characteristics of Influenza A
- Influenza A viruses are further divided into subtypes based on their hemagglutinin (H) and neuraminidase (N) proteins 2, 5.
- Influenza A viruses can infect a wide range of hosts, including humans, animals, and birds 3, 4.
- Influenza A viruses are known to cause more severe illness and higher mortality rates compared to Influenza B viruses 3, 4.
Treatment and Prevention of Influenza A
- Antiviral medications such as oseltamivir and zanamivir can be used to treat Influenza A infections 2, 3, 4, 5, 6.
- Vaccination is the most effective way to prevent Influenza A infections, especially in high-risk populations such as the elderly and young children 3, 4.
- Early treatment with antiviral medications can reduce the duration and severity of Influenza A illness, as well as reduce the risk of complications and transmission to others 2, 5, 6.