Group A Streptococcus (Streptococcus pyogenes) causes the common illness known as strep throat. This bacterial infection of the throat and tonsils is particularly prevalent in school-age children, but it affects people of all ages. When strep throat is confirmed, the standard course of action is to prescribe a short regimen of antibiotics, typically penicillin or amoxicillin. Treatment eliminates the bacteria, relieves immediate discomfort, and prevents rare, yet devastating, long-term health problems. Understanding what happens when this infection is left untreated reveals its serious nature.
Symptom Persistence and Contagiousness
Without antibiotic intervention, the body’s immune system will eventually fight off the Streptococcus pyogenes infection, but the recovery process is significantly prolonged. The hallmark symptoms of strep throat, such as severe sore throat, fever, and difficulty swallowing, will likely persist for about a week, or potentially even longer. In contrast, patients who begin antibiotics usually experience a noticeable improvement in their symptoms within 24 to 48 hours.
A major difference between treated and untreated infection lies in the length of the contagious period. An individual with strep throat remains highly contagious as long as the bacteria are present in the throat and saliva. For those who do not take antibiotics, this period can last for two to three weeks, even after acute symptoms have started to fade.
Starting antibiotics quickly eliminates the bacteria from the respiratory tract. A person is generally considered non-contagious after they have been on the prescribed antibiotic for a full 24 hours and their fever has resolved. This rapid cessation of contagiousness is a public health benefit, allowing children and adults to return to school and work much sooner and preventing community transmission.
The Critical Danger of Rheumatic Fever
The prevention of Acute Rheumatic Fever (ARF) is a primary reason for treating strep throat with antibiotics. This condition is an immune-mediated reaction that occurs after the initial infection. ARF typically develops two to four weeks after an untreated strep throat infection in susceptible individuals.
The body’s immune response to the Streptococcus pyogenes bacteria creates antibodies that mistakenly attack healthy tissues in the body. The main targets of this misdirected attack are the joints, skin, brain, and the heart.
Inflammation in the heart can damage the heart valves, a condition known as Rheumatic Heart Disease (RHD). This permanent damage can lead to heart failure or the need for valve replacement surgery later in life. The joints can become painful and inflamed, causing a migratory arthritis that moves from one joint to another.
In the brain, the attack can manifest as Sydenham chorea, a neurological disorder characterized by involuntary, jerky movements and emotional instability. The primary goal of a 10-day antibiotic course is to eradicate the bacteria completely, which prevents this autoimmune cascade from ever being initiated.
Other Severe Infections and Systemic Damage
Untreated strep throat can lead to the development of Post-streptococcal Glomerulonephritis (PSGN), an inflammatory condition affecting the kidneys. This complication is also an immune response, involving the deposition of immune complexes in the kidney’s filtering units.
PSGN can lead to symptoms like dark-colored urine, swelling, and high blood pressure, appearing about 10 days after the initial throat infection. While most cases resolve completely, it can rarely cause long-term kidney damage.
The bacterial infection can also spread directly to nearby tissues, resulting in suppurative complications. The bacteria can create a peritonsillar abscess, commonly called Quinsy, which is a collection of pus behind the tonsil causing severe throat pain and difficulty opening the mouth.
Other localized infections include cervical lymphadenitis (severe inflammation of the neck lymph nodes) or mastoiditis (an infection of the mastoid bone behind the ear). A final consequence is the potential link between strep infection and Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS). In susceptible children, an untreated strep infection can trigger the sudden onset or worsening of symptoms like obsessive-compulsive disorder (OCD) or tic disorders.