Family doctor

Overview:

• A sore throat is also known as pharyngitis
• It is usually caused by either a bacterial or viral infection
• Approximately 90% of cases are caused by viruses
• Strep throat is the most common bacterial infection and is caused by the bacteria group A streptococci (approximately 10%)
• A sore throat is contagious in most cases and is spread through coughing and sneezing
• Sometimes a sore throat is a signal of another underlying medical condition

What is it?

A sore throat is caused by inflammation at the back of the throat. The proper medical term is pharyngitis.

Most sore throats are caused by a bacterial or viral infection, and can be the first sign of a cold or flu starting.

The majority of sore throats are caused by viruses which are spread by coughing, sneezing, kissing and sharing cups and utensils with someone who has the illness. Bacterial causes of sore throats are also contagious.

The tonsils are thought to be part of the first line of the body's defence against potentially harmful germs. Bacteria or viruses enter the mouth or nose and are "picked up" in the tonsils or adenoids, and infection here can cause them to swell. Tonsillitis is an infection mainly in the tonsils which are areas of spongy tissue on the side of the back of the throat.

What are the causes?

Bacterial infection

Strep throat is the most common bacterial infection. About 10 percent of people with a sore throat will have strep throat which is an infection with group A streptococci. (See our article on strep throat).

Strep throat can lead to rheumatic fever in rare cases which can trigger heart valve problems or inflammation of the kidney. These complications are extremely rare (after approximately 1 in 50,000 sore throats) and the exact mechanism of rheumatic fever is not clear; only 50 percent of cases are associated with sore throats in any event.

Some areas, including in New Zealand, are associated with a higher risk of rheumatic fever.

Strep throat can also rarely cause a red rash known as scarlet fever. But this is no more dangerous than strep throat without the rash.

Strep throat is diagnosed with swabs taken of the infected area which are sent to a laboratory for testing. Swab testing is not always required in cases where a viral cause is likely. Your doctor can discuss the need for tests if necessary.

Rarely other bacteria can cause sore throats - e.g. gonorrhoea is an example of a sexually transmitted infection.

Viruses

The majority of sore throats are due to an infection with a virus; there is a large variety of viruses which cause the common types of sore throats.

A well-known virus is the Epstein-Barr virus, which causes glandular fever and glandular fever tonsillitis (see below).

Tonsillitis

This term is used for an inflammation of the tonsils themselves, and does not apply to sore throats which cover the wider throat area.

Some people suffer recurrent tonsillitis, especially children and young adults. Chronic tonsillitis occurs when there is so much damage to the tonsils that they remain infected and do not respond well to antibiotic treatment. In this condition, the throat is sore most of the time, often accompanied by bad breath (halitosis).

Surgery to remove the tonsils is often recommended for recurrent tonsillitis.

Glandular fever and tonsillitis

Glandular fever may cause a severe attack of tonsillitis. The tonsils and the glands in the neck are often very large and may cause severe breathing difficulties.

There is often a gray coating over the tonsils. There may be a rash on the skin or sometimes over the soft palate. The infection often causes enlargement or inflammation of the liver and spleen. In this case care must be taken to avoid minor abdominal trauma as the spleen may potentially rupture, causing severe intra-abdominal bleeding. Contact sport is advised against for a few months because of this.

Alcohol must be avoided when the liver is enlarged. The diagnosis of glandular fever is confirmed by a blood test looking for the presence of the Epstein-Barr virus or looking for abnormal lymphocytes (a type of white blood cell). The blood test for glandular fever may not be positive at the time of the sore throat and usually takes a few weeks to become positive.

Quinsy (peritonsillar abscess)

Quinsy is an abscess, which forms on one side of the palate and throat around the tonsil, and may follow tonsillitis. It causes persistent symptoms of severe tonsillitis, which may fail to respond to oral antibiotics unless the abscess is drained. Often there is severe difficulty drinking and swallowing, and dehydration can result.

Increasing pain, fever and difficulty swallowing are warning signs of this condition.

Other possible causes:

• Laryngitis (losing your voice or croaky voice)
• Diphtheria (now a rare disease thanks to immunisation)
• Measles
• Breathing through the mouth can cause the throat to dry and become painful
• Draining from the sinuses can cause throat irritation
• In some cases a sore throat could be a sign of throat cancer (usually in smokers) or AIDS (unusual infections or severe thrush/candida)

What are the symptoms?

The symptoms for a sore throat caused by both bacterial and viral causes are the same; they include pain with swallowing, red throat, swollen tonsils, swollen neck glands, pus covering the throat, coughing, and possibly a fever.

Patients may also suffer from a headache, stomach ache, and their voice may become hoarse. They may experience nausea and vomiting if they have the flu or another illness.

Most people's throats will begin to feel better within three to five days after the start of the illness.

What can be done?

Sore throats caused by a virus do not respond to antibiotics but there are several measures that can be taken to help reduce the discomfort:

• Gargle with a cup of warm water and 1/2 a teaspoon of salt
• Suck throat lozenges or use throat sprays
• Use a pain reliever such as paracetamol every four hours
• Drink plenty of water, soft drinks or milkshakes (water or electrolyte solutions are best if the patient is vomiting)
• Eat soft foods such as ice cream, soups and mashed vegetables
• Avoid smoking because this can cause further throat irritation

Antibiotics can be used to cure a sore throat caused by bacteria such as strep throat. However, the rationale of this is being increasingly questioned, particularly in countries and areas where the risk of rheumatic fever is extremely low.

A Cochrane review of the medical literature has found that 90 percent of patients with a sore throat feel better within one week, regardless of whether they are treated with antibiotics or not.

Studies have found that a small number of people treated with antibiotics feel better after three days compared to those not taking medicine, but this is only a marginal benefit.

Studies from the 1950s show that the use of antibiotics does reduce the rate of rheumatic fever following strep throat but this illness is rare.

The decision to take antibiotics should be weighed against the potential side effects of the drugs including diarrhoea, skin rashes, thrush (candida), and the rare occurrence of anaphylaxis and the risk of bacterial resistance to antibiotics.

There is also concern that the infection can recur when strep throat has been treated with antibiotics.

Antibiotics may be required for people who are seriously ill. They are also generally advised in parts of the world where rheumatic fever is common. They may also be recommended if there is also an accompanying ear infection with a sore throat.

If antibiotics are prescribed they must be taken for at least 10 days in order to destroy the bacteria. Commonly prescribed antibiotics include amoxicillin (avoid in glandular fever), penicillin (this is the drug of choice), and erythromycin (drug of choice if allergic to penicillin).

Getting help

Your doctor will be able to advise on the best treatment for a sore throat. Immediate medical attention is required if the patient can hardly swallow, is drooling, or having trouble breathing.

Most sore throats do not require medical attention. However, if a child has a sore throat associated with severe symptoms or fever, medical advice should be sought from your doctor.

If a sore throat does not resolve in a week or so, or if you are concerned about other associated symptoms (e.g. earache or headache) it is also wise to seek advice.