Acute pharyngitis is inflammation of the back of the throat that comes on suddenly, causing the sore throat most people experience several times a year. Viruses cause the majority of cases, while bacteria, most notably the strep bacteria, account for roughly 5% to 36% depending on the population and season. Symptoms typically peak within 3 to 5 days and resolve by day 10, though bacterial cases sometimes need antibiotics to prevent rare but serious complications.
What Happens Inside Your Throat
When a virus or bacterium reaches the tissue lining the back of your throat, it invades the surface directly. Your immune system responds with inflammation, which causes swelling and extra mucus production. That combination of swollen tissue and excess secretion is what makes swallowing painful and your throat feel raw. Some viruses, like the common cold virus, also trigger irritation indirectly through nasal drainage that drips down the back of the throat.
Viral vs. Bacterial Causes
The most common culprits are viruses you already know: the common cold virus (rhinovirus), flu, adenovirus, coronavirus, and parainfluenza. Less frequently, Epstein-Barr virus (the cause of mono), herpes viruses, and coxsackievirus can be responsible. Viral pharyngitis often comes packaged with a runny nose, cough, and watery eyes, which helps distinguish it from bacterial infections.
The bacterial cause that matters most is Group A strep, the one behind “strep throat.” It accounts for 5% to 36% of acute pharyngitis cases, with the higher end seen in children during winter and early spring. Other bacteria can cause pharyngitis too, but strep is the one clinicians screen for because it carries the risk of complications that other common causes do not.
What It Feels Like
The core symptoms are a sore throat, pain when swallowing, and often a fever. Beyond that, the details depend on the cause. Viral pharyngitis tends to come with cold symptoms: congestion, cough, sneezing, and a general run-down feeling. Strep throat is more likely to hit without a cough, with a fever at or above 100.4°F (38°C), visibly swollen or pus-covered tonsils, and tender, swollen lymph nodes just below the jaw. These differences aren’t absolute, but they form the basis of how doctors decide whether testing is worthwhile.
How Doctors Tell Viral From Bacterial
Clinicians use a checklist called the Centor criteria to estimate the likelihood that strep is the cause. You get one point for each of four signs: fever of 100.4°F or higher, no cough, swollen front neck lymph nodes, and swollen or pus-covered tonsils. Scores range from 0 to 4.
A score of 3 or 4 strongly suggests strep and is over 96% accurate at identifying who does and doesn’t have it. A low score makes strep unlikely, and testing may not be necessary. For scores in the middle, a rapid strep test or throat culture confirms the diagnosis. The key point for you: a sore throat with a cough and runny nose is almost certainly viral and won’t benefit from antibiotics.
How Long It Lasts
Whether viral or bacterial, symptoms typically peak between days 3 and 5, then gradually improve and resolve by day 10. Interestingly, even for confirmed strep throat, there is growing evidence that delaying antibiotic treatment by up to 3 days may not meaningfully prolong recovery. That said, antibiotics for strep serve a purpose beyond symptom relief: they prevent complications.
Treatment for Bacterial Pharyngitis
When strep is confirmed, the standard treatment is a 10-day course of penicillin or amoxicillin. These remain the first-line antibiotics because strep bacteria have not developed resistance to them. The full 10 days matter even if you feel better within a few days, because the goal is to fully eliminate the bacteria and reduce the risk of complications like rheumatic fever. For people with a penicillin allergy, alternative antibiotics are available.
In some cases, particularly when a patient is unlikely to complete a 10-day oral course, a single injection of long-acting penicillin accomplishes the same thing in one visit.
Relieving Symptoms at Home
Since most pharyngitis is viral and antibiotics won’t help, symptom relief is the main treatment for the majority of sore throats. Several simple measures make a real difference:
- Warm fluids: Broth, caffeine-free tea, or warm water with honey soothes irritated tissue and keeps the throat moist. Avoid caffeine and alcohol, which are dehydrating.
- Saltwater gargles: Dissolving 1/4 to 1/2 teaspoon of salt in 4 to 8 ounces of warm water and gargling can reduce throat pain. This works for children over 6 and adults.
- Staying hydrated: Extra fluids help thin mucus and keep swollen tissue from drying out, which worsens pain.
- Over-the-counter pain relievers: Ibuprofen or acetaminophen can lower fever and ease throat pain.
One important note: honey should not be given to children under age 1 due to the risk of infant botulism.
Why Strep Throat Needs Treatment
The reason strep gets so much attention compared to viral sore throats comes down to complications. Historically, about 3% of people with untreated strep pharyngitis develop rheumatic fever, a condition where the immune system mistakenly attacks the heart, joints, and nervous system. For someone who has already had rheumatic fever, the recurrence rate after another untreated strep infection jumps to roughly 50%.
Rheumatic fever rates vary enormously by region. In the United States, the annual incidence is about 10 per 100,000 people. In India, it rises to 51 per 100,000. Among Indigenous populations in Australia, rates reach 150 to 380 per 100,000 children aged 5 to 14, some of the highest in the world. These numbers explain why prompt identification and treatment of strep remains a public health priority, even though the sore throat itself resolves on its own.
Beyond rheumatic fever, untreated strep can also lead to peritonsillar abscess (a pocket of pus forming beside the tonsil) and, rarely, kidney inflammation. These complications are uncommon with appropriate antibiotic treatment.