Strep throat is a common bacterial infection of the throat and tonsils caused by Group A Streptococcus (GAS), also known as Streptococcus pyogenes. While the immediate discomfort is noticeable, the primary danger of leaving the infection untreated is not the acute illness itself, but the serious, long-term complications that can follow. Understanding the consequences of persistent bacteria highlights why medical treatment is important.
The Acute Illness Without Treatment
If strep throat is left untreated, immediate symptoms like fever, sore throat, and painful swallowing will last longer than if antibiotics were used. Without medication, the immune system fights the infection alone, meaning symptoms can persist for seven to ten days instead of resolving quickly with treatment. The Streptococcus bacteria may still be present even if the person feels better. An individual with untreated strep remains contagious for two to three weeks, increasing the risk of spreading the infection. The timing of antibiotic treatment determines the window for preventing serious systemic complications.
Localized Infections and Immediate Risks
The presence of multiplying GAS bacteria creates an immediate risk for localized infections in adjacent tissues. A painful and immediate complication is a peritonsillar abscess, often called quinsy, which is a collection of pus near a tonsil. This infection causes severe, unilateral throat pain, a muffled “hot potato” voice, and difficulty opening the mouth (trismus). A peritonsillar abscess requires immediate medical attention, often involving drainage in addition to antibiotic therapy.
The infection can also spread to other connected structures in the head and neck. This spread may result in otitis media, an infection of the middle ear, or acute sinusitis, an inflammation of the sinuses. These conditions arise when the bacteria travel from the infected throat tissue through connecting passages. While treatable, they require more intensive medical intervention than the initial strep infection alone.
Severe Systemic Complications
The most serious consequences of untreated strep throat involve the body’s immune response, which can affect distant, vital organ systems. The body produces antibodies to fight GAS bacteria, but these antibodies mistakenly attack healthy tissues because bacterial proteins resemble proteins found in the body. This phenomenon, known as molecular mimicry, leads to severe autoimmune complications, not direct bacterial attack on the organs.
One such complication is Acute Rheumatic Fever (RF), which typically appears two to four weeks after the initial strep infection. RF causes inflammation in the heart, joints, brain, and skin. The most damaging effect is on the heart valves, where repeated episodes lead to permanent scarring and damage known as Rheumatic Heart Disease (RHD). RHD can weaken the heart and lead to lifelong cardiac problems.
Another serious immune-mediated response is Post-Streptococcal Glomerulonephritis (PSGN), which causes inflammation in the tiny filtering units of the kidneys. PSGN develops about ten days after infection and leads to symptoms like blood in the urine, facial swelling, and high blood pressure. Unlike Rheumatic Fever, antibiotic treatment of the initial strep infection does not reliably prevent PSGN, as the kidney damage process is often already initiated. While most people recover fully, a small number of adults may develop long-term kidney damage.
The Primary Goal of Antibiotic Therapy
The primary reason medical professionals strongly recommend antibiotics for strep throat, even with mild symptoms, is to prevent the development of Acute Rheumatic Fever (RF). Antibiotics are highly effective at eliminating GAS bacteria, and treatment initiated within nine days of symptom onset can stop the chain of events leading to RF. The ten-day course of medication is timed to eradicate the bacteria before the autoimmune response is triggered, preventing permanent heart damage.
A secondary benefit of treatment is the rapid reduction in transmissibility. By eliminating the bacteria quickly, antibiotics render the infected person non-contagious within approximately 24 hours, which helps protect others from exposure.