Streptococcal Infection

Overview

Streptococcal (strep) infections are caused by streptococcus bacteria, a large group of organisms that can affect the throat, skin, and other parts of the body. Two important groups are group A streptococcus, which causes strep throat, scarlet fever, and many skin infections, and group B streptococcus, which can affect newborns and some adults.

Most strep infections, such as strep throat and impetigo, are common and respond well to antibiotics. Less commonly, strep bacteria can cause severe, invasive infections that spread to the blood, lungs, or deep tissues and require urgent treatment. Prompt diagnosis and the right antibiotics are important both to relieve illness and to prevent complications.

Symptoms

Symptoms depend on where the infection is:

• Strep throat: Sudden sore throat, pain on swallowing, fever, swollen tender neck glands, and red or white-spotted tonsils, usually without a cough.
• Scarlet fever: A fine, sandpaper-like red rash with a sore throat and fever.
• Skin infections: Impetigo causes crusted sores; cellulitis causes spreading redness, warmth, swelling, and pain.

Warning signs of a serious invasive infection include rapidly spreading redness or severe pain out of proportion to the appearance, high fever, confusion, a widespread rash, low blood pressure, or feeling very unwell. These require emergency care.

Causes

Strep infections are caused by streptococcus bacteria and spread in different ways depending on the type:

• Respiratory spread: Strep throat and scarlet fever spread through respiratory droplets from coughing, sneezing, or sharing food and drinks.
• Skin contact: Skin infections can spread through direct contact with sores or contaminated surfaces, often entering through breaks in the skin.

Some people carry strep bacteria without being ill (carriers). Invasive infections occur when bacteria reach normally sterile parts of the body, such as the blood or deep tissues.

Risk Factors

• Close contact with an infected person, such as in households and schools
• Young age (strep throat is most common in children)
• Breaks in the skin from cuts, wounds, or skin conditions
• A weakened immune system or certain chronic illnesses
• Crowded living conditions

Diagnosis

Diagnosis depends on the type of infection:

• Rapid strep test and throat culture: A throat swab can quickly detect group A strep, with a culture used to confirm if needed.
• Physical examination: Skin infections are often diagnosed by their appearance.
• Blood and tissue tests: For suspected invasive infections, blood cultures and other tests identify the bacteria and guide treatment.

Treatment

Most streptococcal infections are treated effectively with antibiotics:

• Antibiotics: Penicillin or amoxicillin are commonly used; alternatives are available for people with penicillin allergy. Completing the full course is important.
• Supportive care: Rest, fluids, and over-the-counter pain and fever relief ease symptoms.
• Wound and skin care: Keeping skin infections clean and covered.
• Hospital treatment: Severe or invasive infections may need intravenous antibiotics, surgery to remove infected tissue, and intensive care.

Treating strep throat with antibiotics also helps prevent complications such as rheumatic fever.

Prevention

• Wash hands often, especially after coughing, sneezing, and before eating
• Cover coughs and sneezes
• Avoid sharing utensils, cups, and personal items with someone who is infected
• Keep cuts and wounds clean and covered until healed
• Stay home and complete antibiotics as prescribed if you have strep throat to avoid spreading it

When to See a Doctor

See a doctor for a sore throat with fever and swollen glands, a spreading or worsening skin infection, or symptoms that do not improve. Seek emergency care immediately if you or your child has:

• Rapidly spreading redness or severe pain out of proportion to how the skin looks
• High fever with confusion, dizziness, or feeling very unwell
• Difficulty breathing or swallowing
• A widespread rash with low blood pressure or signs of shock

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Group A Streptococcal (GAS) Disease.
2. Mayo Clinic. Strep throat — Symptoms and causes.
3. MedlinePlus, U.S. National Library of Medicine. Streptococcal infections.
4. National Institute of Allergy and Infectious Diseases (NIAID).