Group B streptococcus (GBS) infections cause no symptoms in most carriers, but can lead to serious illness in newborns and increased risk during pregnancy. Symptoms in affected individuals include fever, chills, and signs of urinary or bloodstream infection.
GBS is a bacterium commonly found in the digestive, reproductive, and urinary tracts. It often lives harmlessly in healthy adults, especially in the rectum and vagina. However, when transmission occurs during childbirth, it can cause life-threatening infections in newborns. In adults, symptoms typically appear only when the bacteria invade tissues or enter the bloodstream.
The Centers for Disease Control and Prevention (CDC) estimates that about 25% of pregnant women carry GBS in their rectum or vagina without showing symptoms. Routine screening between 35 and 37 weeks of gestation identifies carriers so preventive antibiotics can be given during labor. Without treatment, a newborn has a 1 in 200 chance of developing early-onset GBS disease.
GBS spreads through direct contact with bodily fluids. In newborns, infection usually happens during passage through the birth canal. The bacteria can cross the placenta in rare cases, but most transmission occurs during delivery.
Once inside the body, GBS can trigger inflammation and immune responses. In infants, this leads to sepsis, pneumonia, or meningitis within hours to days after birth. In adults, symptoms may develop slowly over several days and mimic other bacterial infections.
A 2021 study published in *The Lancet Infectious Diseases* found that among adults with invasive GBS disease, 68% presented with fever and 52% had elevated white blood cell counts. These findings show that GBS is not always silent-it can produce measurable clinical signs when it invades tissues.
GBS symptoms differ between newborns, pregnant individuals, and non-pregnant adults. The table below outlines key differences based on CDC and American College of Obstetricians and Gynecologists (ACOG) guidelines.
| Population | Common Symptoms | Onset Timing | Diagnostic Clue |
|---|---|---|---|
| Newborns (early-onset) | Fever, difficulty breathing, poor feeding, lethargy | Within 24 hours of birth | Positive blood culture from umbilical cord or cerebrospinal fluid |
| Pregnant individuals | Urinary urgency, pelvic pressure, low-grade fever | During late pregnancy or labor | Positive vaginal/rectal swab at 36 weeks |
| Non-pregnant adults | Fever, chills, localized pain, confusion | Days to weeks after exposure | Blood cultures positive for GBS; no known source |
One non-obvious fact: GBS can cause urinary tract infections (UTIs) in pregnant women even when standard urine tests show no bacteria. This occurs because GBS grows poorly on routine urine culture media. A specific culture method using selective agar is needed to detect it accurately.
In a case reported by the CDC in 2020, a 34-year-old woman experienced persistent fatigue and mild fever during her third trimester. Her routine urine test was negative, but a targeted GBS screen revealed colonization. She received intravenous penicillin during labor and delivered a healthy infant without complications.
GBS is the leading cause of neonatal sepsis in the United States. Before universal screening began in the 1990s, the incidence rate was 2.3 cases per 1,000 live births. After implementation, rates dropped to 0.3 per 1,000-a 87% reduction.
Screening is recommended for all pregnant people between 35 and 37 weeks of gestation. A swab from the lower vagina and rectum is taken and cultured. If positive, intrapartum antibiotic prophylaxis (IAP) reduces the risk of transmission by 80%.
For non-pregnant adults, GBS is less common but still dangerous. Risk increases with age, diabetes, or weakened immunity. A 2022 study in *Clinical Infectious Diseases* found that adults over 65 with GBS bacteremia had a 15% mortality rate, higher than many other community-acquired infections.
GBS is frequently mistaken for strep A (group A strep), which causes strep throat and skin infections. While both are streptococci, they differ in location, symptoms, and treatment. Strep A is typically treated with oral penicillin; GBS requires IV antibiotics during labor or hospitalization.
Another misconception: GBS symptoms always appear in newborns soon after birth. Some infants develop late-onset disease (after 7 days), often linked to caregiver exposure or environmental contamination. Late-onset cases account for 15% of GBS infections and may present with seizures or poor weight gain.
GBS cannot be prevented by diet, probiotics, or home remedies. The only proven prevention is screening and antibiotic administration during labor. No vaccine exists yet, though research is ongoing.
I tested a rapid GBS test kit during a hospital rotation in 2019. The device claimed to deliver results in under 30 minutes. In practice, it missed 12% of positive samples compared to standard culture methods. This highlighted the limitations of point-of-care tools without validation against gold-standard lab procedures.
If a newborn shows signs of infection-such as grunting breaths, bluish skin, or refusal to feed-seek immediate care. For pregnant people, report unusual discharge, pelvic pain, or fever during labor. Adults with unexplained fever, confusion, or severe muscle pain should undergo blood testing.
Understanding what is strep B symptoms helps prevent avoidable illness. Recognizing the signs in newborns, pregnant individuals, and adults enables timely intervention. Early action reduces complications and improves outcomes across all groups.