Strep throat, or streptococcal pharyngitis, is a bacterial infection of the throat and tonsils caused by Streptococcus pyogenes, also known as Group A Streptococcus (GAS). While it may present as a common sore throat, neglecting diagnosis and treatment allows the GAS organisms to persist. This persistence leads to a cascade of acute and delayed complications that extend far beyond the throat. Understanding these consequences highlights why prompt medical attention is necessary, as an untreated infection can become a severe health concern.
Acute Progression and Localized Risks
If the bacterial infection remains unchecked, initial symptoms like severe throat pain, difficulty swallowing, and high fever will worsen and persist. The untreated bacteria can spread from the tonsils to nearby anatomical structures, leading to localized infectious complications, known as suppurative complications. This local spread can result in acute otitis media (middle ear infection) or acute sinusitis (inflammation of the paranasal sinuses).
The most serious localized risk is the development of a peritonsillar abscess, often called Quinsy. This condition occurs when the infection breaks out of the tonsil and forms a painful, pus-filled pocket in the surrounding tissue. The abscess causes severe, often unilateral, throat pain and makes it difficult to open the mouth or swallow saliva.
An untreated peritonsillar abscess is a serious medical emergency because swelling can obstruct the airway, making breathing difficult. If the abscess ruptures, the infected material can travel into the neck or chest, potentially causing severe infections like pneumonia or systemic bloodstream infections. These acute complications demonstrate the danger of allowing bacterial colonization to continue.
Severe Systemic Complications
Beyond local spread, the body’s immune response to Group A Streptococcus can trigger severe, delayed, and systemic inflammatory diseases, known as non-suppurative complications. These are caused by an autoimmune reaction that typically manifests two to four weeks after the initial infection. This phenomenon is driven by molecular mimicry, where the immune system mistakenly attacks the body’s own tissues because they share structural similarities with bacterial antigens.
One concerning systemic consequence is Acute Rheumatic Fever (ARF), an inflammatory condition affecting multiple organ systems. ARF can cause arthritis that migrates from joint to joint, a characteristic rash (erythema marginatum), and involuntary movements (Sydenham chorea). The most significant long-term damage occurs when inflammation affects the heart, a condition called carditis, which can lead to permanent scarring of the heart valves.
This irreversible damage to the heart valves is termed Rheumatic Heart Disease (RHD). RHD can develop after a single severe episode or repeated bouts of ARF. The scarred valves may become narrowed or leaky, leading to serious cardiovascular issues, including heart failure and an increased risk of stroke later in life. RHD remains a significant cause of acquired heart disease globally.
Another immune-mediated complication is Post-Streptococcal Glomerulonephritis (PSGN), which affects the kidneys. This condition occurs when immune complexes, formed while fighting the bacteria, become trapped and deposit in the glomeruli (the small filtering units of the kidneys). PSGN typically appears one to two weeks following the infection and can cause symptoms like dark, reddish-brown urine, swelling (edema), and high blood pressure.
While most children recover fully from PSGN, adults and individuals with pre-existing conditions have a worse prognosis, potentially progressing to chronic kidney dysfunction or failure. Additionally, certain strains of S. pyogenes that produce an erythrogenic toxin can result in scarlet fever. Scarlet fever presents with a characteristic fine, sandpaper-like red rash and a “strawberry tongue.” This condition requires prompt antibiotic treatment to prevent progression to other serious conditions.
Resolution Through Antibiotic Treatment
The severe risks associated with untreated strep throat are largely avoidable through a straightforward course of antibiotic medication. The primary treatment goal is not just to relieve acute symptoms but also to prevent the development of immune-mediated complications like Acute Rheumatic Fever. Antibiotics, such as penicillin or amoxicillin, are the preferred treatments because they are highly effective against Group A Streptococcus.
Treatment needs to be initiated promptly, ideally within nine days of symptom onset, to effectively prevent ARF. Beyond complication prevention, the medication quickly reduces the duration and severity of the sore throat and fever. It also significantly reduces the risk of spreading the infection to others; a person is typically no longer contagious after taking the antibiotic for at least 24 hours.
A full course of antibiotics, typically lasting 10 days, must be completed as prescribed, even if symptoms rapidly improve. Stopping the medication early allows residual bacteria to survive, risking recurrence of the infection and increasing the chance of developing serious complications. Diagnosis is confirmed through a rapid strep test or throat culture before initiating treatment, ensuring that only bacterial infections receive antibiotics.