Strep throat is an infection caused by bacteria called Streptococcus pyogenes, also known as group A Streptococcus (GAS). When you get strep throat, these bacteria infect the throat and tonsils, leading to inflammation and other characteristic symptoms.

Here's a breakdown of what happens:

1. Infection: The bacteria enter your body, usually through close contact with someone who is already infected. This can happen through respiratory droplets (coughing, sneezing) or by sharing food or drinks.
2. Colonization: The bacteria attach to the lining of your throat and tonsils, where they begin to multiply.
3. Inflammation: As the bacteria multiply, they release toxins and trigger an immune response. This leads to inflammation of the throat and tonsils.
4. Symptoms: The inflammation and immune response cause the typical symptoms of strep throat.

Common symptoms of strep throat include:

• Sore throat: This is usually a sudden onset of pain, and it can be severe.
• Pain when swallowing: Swallowing can be very painful due to the inflammation.
• Red and swollen tonsils: The tonsils often appear red and inflamed, and they may have white patches or streaks of pus.
• Tiny red spots on the soft or hard palate: These are called petechiae.
• Swollen, tender lymph nodes in the neck: The lymph nodes under your jaw may become swollen and painful to the touch.
• Fever: A fever is common with strep throat.
• Headache: You may experience a headache.
• Stomach ache, nausea, or vomiting: These symptoms are more common in children.
• Body aches: General body aches can occur.

It's important to see a doctor if you suspect you have strep throat, as it requires antibiotic treatment to prevent complications such as rheumatic fever.

Source: Centers for Disease Control and Prevention (CDC)