Flu Virus 101 | National Geographic
The Elusive Flu Virus: Understanding Its Impact and Mechanisms
Overview of the Influenza Virus
- The flu is a highly contagious respiratory illness, causing over 36,000 deaths annually in the U.S. and responsible for some of history's deadliest pandemics.
- The influenza virus is a parasite composed of ribonucleic acid (RNA) encased in proteins, specifically hemagglutinin (HA) and neuraminidase (NA).
Mechanism of Infection
- HA protein facilitates the attachment of the virus to host cells, allowing entry; once inside, the virus multiplies.
- NA protein releases newly formed viral particles to infect additional cells, triggering an immune response that can lead to tissue destruction.
Immune Response and Consequences
- The immune system's attack on infected tissues can inadvertently cause organ failure or secondary infections like bacterial pneumonia.
Mutation and Strain Variability
- The flu virus has proven difficult to eradicate due to its rapid mutation rate; since 2004, over 5,000 strains have been sequenced.
- Human-infecting strains are categorized as types A, B, or C; Type A strains are particularly adept at causing pandemics due to their ability to mutate quickly.
Historical Context and Ongoing Threat
- Notable pandemics include the Spanish flu (1918-1919), caused by H1N1 strain from birds, which infected one-third of the global population and resulted in up to 50 million deaths.
- Scientists continuously monitor influenza viruses and develop seasonal vaccines as a primary defense against potential outbreaks.