Viral vs bacterial tonsillitis: causes and treatments
What is tonsillitis?
Tonsillitis is a condition where the tonsils at the back of your throat become red, swollen, and painful. It is an inflammation of the tonsils, which is a symptom of an underlying infection rather than an illness in itself. While most frequently seen in children, tonsillitis can affect anyone of any age.
The role of your tonsils
Your tonsils are two small, oval-shaped glands located on either side of the back of your throat. They’re part of yourbody's immune system. Because of their location, they act as a first line of defence against germs entering through your mouth and nose. When viruses or bacteria enter your body, your tonsils trap these pathogens and produce antibodies to help fight off the infection, which is why they often become inflamed and sore in the process.
Differences between viral and bacterial tonsillitis
You can often distinguish between viral and bacterial tonsillitis by looking at the specific combination of symptoms, how quickly they appear, and the visual appearance of the throat.
Viral tonsillitis symptoms
Viral tonsillitis is the most common form of the condition. About two thirds of cases are caused by a virus, according to NHS England. Because it's often caused by the same viruses as colds and flu, it often presents alongside typical cold or flu-like symptoms. Key indicators include a sore throat, a low-grade fever, a cough, a runny or stuffy nose, and hoarseness. If you have a cough and a runny nose, your tonsillitis is more likely to be viral.
Bacterial tonsillitis symptoms
Bacterial tonsillitis symptoms tend to be more sudden and severe. The key indicators of a bacterial infection are a very painful sore throat that comes on quickly, difficulty swallowing, a fever above 38C, and swollen, tender lymph nodes in the neck. Crucially, a bacterial infection is usually accompanied by a noticeable lack of a cough.
Key differences at a glance
|
Feature |
Viral Tonsillitis |
Bacterial Tonsillitis |
|---|---|---|
|
Onset |
Gradual |
Can be more sudden |
|
Key Symptoms |
Sore throat, runny nose, hoarseness |
Severe throat pain, painful swallowing |
|
Fever |
Often milder |
Often 38C or above |
|
Cough? |
Yes, very common |
No, usually absent |
|
Appearance of Tonsils |
Red and swollen |
Red and swollen with white/yellow pus spots |
|
Common Cause |
Viruses, such as those that cause colds and flu |
Group A Streptococcus bacteria |
|
Treatment |
Rest, fluids, over-the-counter painkillers |
Antibiotics if prescribed, plus symptom relief |
Causes of tonsillitis
Tonsillitis is caused by everyday pathogens passing from person to person, most commonly respiratory viruses or streptococcal bacteria.
Viral causes
The same common viruses that cause colds and flu, such as rhinovirus and adenovirus, are the most frequent culprits behind tonsillitis. In my experience as a GP, most patients who seek support for throat pain are dealing with one of these everyday respiratory viruses. Another notable cause is the Epstein-Barr virus. This virus causes glandular fever, which is also known as infectious mononucleosis. Glandular fever often causes a more severe sore throat and swollen tonsils that take longer to get better, along with extreme tiredness and swollen glands in the neck.
Bacterial causes
When tonsillitis is bacterial, it is usually caused by Streptococcus pyogenes, commonly referred to as Group A Streptococcus. This is the bacteria responsible for what is often called strep throat. Identifying and treating this specific bacterium is important because, while most people recover without issue, untreated streptococcal infections can occasionally lead to more complicated health problems. According to NICE guidance, distinguishing between a viral cause and this specific bacterial cause helps doctors avoid prescribing unnecessary antibiotics.
Diagnosing tonsillitis
A doctor determines the cause of tonsillitis by assessing your symptoms, examining your throat, and using clinical assessment tools to calculate the likelihood of a bacterial infection.
Physical examination
During a consultation, a GP will examine the back of your throat to look for redness, swelling, and pus. They will also ask about your temperature to check whether you have a fever and whether the glands in your neck are swollen and tender.
Our online GPs at Doctor Care Anywhere regularly carry out this assessment through video appointments, with photos where needed. Your GP will guide you through each step, such as using your phone's torch to show the back of your throat, gently feeling your neck glands yourself, and taking your temperature with a thermometer if you have one. If you need to be examined in person, they'll let you know and advise you on the next steps. The Centor score
To estimate whether the infection is bacterial and likely to benefit antibiotics, doctors often use t a scoring system such asthe Centor score, as recommended by NICE guidance. A similar UK tool, called FeverPAIN, is also widely used. The criteria include four main signs:
- White or yellow spots of pus on the tonsils.
- Swollen and tender glands in the neck.
- The absence of a cough.
- A history of a fever over 38C.
Each sign scores one point. If you only meet one or two criteria, the infection is highly likely to be viral and antibiotics won’t help. If you meet three or four, there is a much higher chance it is a bacterial infection, and antibiotics might help.Throat swabs and blood tests
In most cases, doctors diagnose tonsillitis based on your symptoms and a visual examination alone. However, if the diagnosis remains unclear, a doctor might recommend a throat culture swab to confirm the presence of Group A strep bacteria. A blood test is rarely needed for standard tonsillitis, but a GP might recommend one if they suspect you have glandular fever.
Treatments for tonsillitis
The right treatment for tonsillitis depends entirely on whether a virus or bacteria is causing the infection, but simple symptom relief is the starting point for everyone
At-home care
Regardless of the cause, the immediate goal is to make yourself comfortable while your immune system fights the infection. The NHS advises several simple steps for managing symptoms at home:
- Get plenty of rest to help your body recover.
- Drink plenty of cool fluids to stay hydrated and soothe your throat.
- Eat soft foods that are easy to swallow.
- Gargle with warm salty water to relieve pain and reduce swelling (this is not recommended for children).
- Take over-the-counter painkillers like paracetamol or ibuprofen to ease throat pain and bring down a high temperature.
Medical treatment
If a GP diagnoses bacterial tonsillitis, they may prescribe a course of antibiotics. The first-line antibiotic prescribed for streptococcal tonsillitis is phenoxymethylpenicillin, according to the BNF. If you are allergic to penicillin, doctors will usually offer an alternative such as clarithromycin, as listed in the BNF. It is critical to complete the entire course of antibiotics exactly as prescribed, even if you feel better after a few days, to clear the infection fully and prevent complications.
When to seek medical advice
You should seek medical advice if your symptoms are severe, do not improve after a few days, or if you develop signs that suggest a complication.
When to see a GP
Most cases of tonsillitis can be managed safely at home, but you should speak to a GP if:
- Your symptoms show no sign of improvement after four days.
- Your throat is so painful that you are unable to eat or drink.
- You have a persistent high temperature.
- You can see white spots of pus on your tonsils.
- You keep getting tonsilitis
If you are concerned about your symptoms, you can book a GP appointment with a Doctor Care Anywhere clinician for a rapid assessment and professional support.
Red flag symptoms
When to get urgent help
Call 999 if: You have severe difficulty breathing, you have severe difficulty swallowing your own saliva, you are drooling uncontrollably, or your breathing sounds noisy.
Call 111 or go to A&E if: Your voice becomes muffled (sounding like you have a hot potato in your mouth), you cannot open your mouth fully, or you develop a stiff neck.
Recurrent tonsillitis and complications
Most cases of tonsillitis get better without any problems. Complications are rare, but they can happen, occasionally after a single bad episode. If you get tonsillitis often, your GP may discuss whether surgery to remove your tonsils could help.
Recurrent tonsillitis definition
Many people get a sore throat once or twice a winter, but clinical guidelines have a specific definition for recurrent tonsillitis. According to NHS England, tonsillitis is considered recurrent if you have had seven or more episodes in the last year, five or more episodes in each of the last two years, or three or more episodes in each of the last three years.
Tonsillectomy surgery
A tonsillectomy is a surgical procedure to remove the tonsils. Because most tonsillitis gets better on its own, doctors no longer routinely remove tonsils. The Royal College of Paediatrics and Child Health notes that surgery is now reserved for patients who meet the strict criteria for recurrent tonsillitis, and whose infections are so severe that they significantly disrupt normal daily life, such as causing regular absences from school or work.
Rare complications
Rarely, bacterial tonsillitis can lead to serious complications. One risk is quinsy: a painful collection of pus that forms between a tonsil and the wall of the throat. Quinsy usually needs urgent hospital treatment. Another, very rare in the UK, is rheumatic fever, an inflammatory reaction that can develop a few weeks after a group A step infection and can affect the heart, joints, and nervous system..
Frequently asked questions
We frequently hear similar questions from patients who are worried about their sore throat symptoms and how best to manage them.
The difference between tonsillitis and strep throat is that strep throat is a specific bacterial infection, while tonsillitis is a broader condition. Strep throat is caused by the Group A Streptococcus bacterium, and can affect the tonsils and the wider throat. Tonsillitis means inflammation of the tonsils, and most cases are caused by viruses. So strep throat can cause tonsillitis, but most tonsillitis isn’t strep throat.
How long tonsillitis is contagious depends on the underlying cause. The NHS explains that tonsillitis itself isn’tcontagious, but the infections that cause it are. If your tonsillitis is viral, you’re usually contagious for as long as your symptoms, and sometimes for a day or so before they start. If you have bacterial tonsillitis, you’re usually no longer infections 24 hours after starting antibiotics.
There isn't always a clear reason why some adults keep getting tonsillitis. While more common in children, adults can get it too. Some people seem more prone to it, possibly because bacteria can build up in small pockets in the tonsils. Smoking, close contact with young children, and a weakened immune system can also increase your risk. If you keep getting tonsillitis, speak to a GP, who can check for other causes and discuss whether treatment such as tonsil removal might help
Antibiotics for tonsillitis are not always necessary. According to NICE guidance, antibiotics are only appropriate for suspected or confirmed bacterial cases. For most people, a sore throat will resolve on its own within a week. When prescribed for bacterial infections, antibiotics can speed up recovery slightly and lower the risk of rare complications, but they offer no benefit for viral cases.
You cannot get tonsillitis if you have had your tonsils removed. However, you can still contract a very similar sore throat, known as pharyngitis, from the exact same viruses and bacteria infecting the wider pharynx. This includes strep throat, which is caused by group A streptococcus bacteria and can still affect the throat without the tonsils. In very rare cases, small amounts of tonsil tissue left behind after surgery can grow back and become infected, but this is uncommon.
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