The flu, or influenza, is a contagious respiratory illness caused by influenza viruses. Here’s an overview of key aspects:
Types of Influenza Viruses
- Influenza A: This type can infect humans and animals and is responsible for seasonal epidemics and occasional pandemics. It has various subtypes based on two proteins on the virus’s surface (hemagglutinin and neuraminidase).
- Influenza B: Primarily affects humans and is typically less severe than type A. It also has lineages (B/Yamagata and B/Victoria).
- Influenza C: Causes mild respiratory illness and is not associated with epidemics.
- Influenza D: Primarily affects cattle and is not known to infect humans.
Complications
Common symptoms of acid reflux include:
- Heartburn: A burning sensation in the chest, often after eating or when lying down.
- Regurgitation: The sensation of acid backing up into the throat or mouth, which may taste sour or bitter.
- Dysphagia: Difficulty swallowing or a sensation of food getting stuck in the throat.
- Chronic Cough: A persistent cough that may worsen at night.
- Sore Throat: Irritation and discomfort in the throat due to acid exposure.
- Hoarseness: Changes in voice or hoarseness, particularly in the morning.
Complications
While many people recover in a few days, the flu can lead to serious complications, especially in vulnerable populations, including:
- Pneumonia
- Bronchitis
- Sinus and ear infections
- Exacerbation of chronic health problems
Seasonal Trends
Flu season typically occurs in the fall and winter months, with peak activity usually between December and February in temperate regions.