Throat infection with strep bacteria is contagious and can cause a variety of symptoms associated with inflammation of the throat and its nearby structures. Symptoms usually begin within a few days (1-4 days) after contracting the infection (incubation period). Typical signs of strep throat infection are:
swollen, tender lymph nodes on the sides of the neck;
white patches seen on the tonsils and throat.
Some other more non-specific signs and symptoms of strep throat which can also be seen in strep throat due to other causes are:
Read more of the symptoms and signs of strep throat »
What is strep throat?
While many people use the terms sore throat, tonsillitis, and strep throat interchangeably, there are significant clinical differences between these conditions. Understanding the differences can give patients a better idea of how and when to be concerned and when to seek advice from a physician.
Strep throat is only one of many possible causes of throat infection and sore throat. While strep throat is most common in children and adolescents, it can affect people of all ages.
What causes sore throat?
Sore throat has many causes. The most common causes of sore throat are infections of the throat and the surrounding structures. Any inflammation or infection of the pharynx, tonsils, esophagus (the food pipe), or larynx (the top opening part of the windpipe) may cause sore throat.
What are the tonsils and tonsillitis?
The tonsils are red, oval clumps of tissue located at the back and to the sides of the throat. This location allows the tonsils to intercept germs as they enter the body through the nose and throat. They contain infection-fighting cells and antibodies (infection-fighting proteins in the body) that stop the spread of the germs further into the body.
Tonsillitis refers to conditions in which the tonsils become red, sore, and swollen because of inflammation. This is not a specific term, as there are many causes of inflammation of the tonsils. Tonsillitis is a common cause of sore throat.
What are the pharynx and pharyngitis?
The pharynx is the area in the back of the throat shared by the oral cavity and the nasal cavity behind the palate. An infection or inflammation of the pharynx is called pharyngitis. The infectious causes are similar to those causing tonsillitis, which are mainly related to viruses and less commonly to bacterial infection.
Because it is difficult to always distinguish exactly between pharyngitis and tonsillitis, throat infections are commonly referred to as tonsillopharyngitis, which signifies an infection of the tonsils, or pharynx, or both.
Viral causes of throat infection
Viruses are the most common cause of throat infection in children and in adults. Many types of viruses are known to cause throat infection, and their symptoms may be difficult to distinguish from those of a bacterial infection.
Throat infections caused by viruses usually occur in non-winter months.
Bacterial causes of throat infection
Bacterial causes of throat infections (tonsillopharyngitis) require further attention from individuals (and their parents or caregiver if the sick person is a child) and physicians.
Streptococcus, or strep, is the most frequently found bacterial cause of sore throat.
The commonly known strep throat is due to only one member of the Streptococcus family of bacteria. This certain streptococcus (Streptococcus pyogenes) belongs to the Group A Streptococcus bacteria (GAS for short). This group of bacteria is also known to cause infections other than strep throat such as skin infections, soft tissue infections, and pneumonia (lung infection).
There are many other bacteria that may also cause throat infections. Group A Streptococcus is the most common cause in children and adolescents. Mycoplasma, Neisseria, Corynebacterium, Yersinia, and non-Group A Strep bacteria are some of the other bacterial causes of throat infection.
Bacterial throat infections typically occur in the winter months.
How common is strep throat?
Group A streptococcus is the most common bacterial cause of throat infection. Approximately 15% to 30% of tonsillopharyngitis in children between 5 to 15 years of age is caused by group A strep. This age group (5 to 15) has the peak incidence of strep throat infection. In adults, 5% to 10% of cases of pharyngitis are estimated to be caused by strep bacteria.
Some reports suggest that over 600 million cases of strep throat occur annually worldwide.
Is strep throat contagious?
Yes, strep throat is contagious. The most common way to catch strep throat is by contact with an infected person.
Close contact with airborne droplets of an infected individual is the most common way of catching Streptococcus infection. Close quarters such as college dormitories, day care centers, military facilities, schools, and families provide ideal conditions for transmission of strep throat from one person to another. The risk of acquiring strep throat from an affected family member nears 40%. Spread through food-borne outbreaks is less common, but possible.
The risk of being contagious with strep throat diminishes substantially after initiation of proper antibiotic treatment.
What are the signs and symptoms of strep throat?
Throat infection with strep bacteria can cause a variety of symptoms associated with inflammation of the throat and its nearby structures. Symptoms usually begin within a few days (1-4 days) after contracting the infection (incubation period).
With strep throat infection, the throat can become red and swollen. White patches may be visible on the back of the throat and the tonsils, suggesting the presence of pus. The presence of fever, swollen lymph nodes on the sides of the neck, and white patches on the tonsils along with the absence of cough raise the suspicion for strep pharyngitis. Not all of these signs need to be present with strep tonsillopharyngitis. On the other hand, their presence is not specific only to strep throat.
Typical signs of strep throat infection are:
swollen, tender lymph nodes on the sides of the neck (cervical lymphadenopathy);
white patches seen on the tonsils and throat (tonsillar exudates).
Some other more non-specific signs and symptoms of strep throat which can also be seen in tonsillopharyngitis due to other causes are:
The strep throat rash is caused by toxins released from the bacteria, and not necessarily because of the spread of infection to the skin. This rash is also known as scarlet fever, which can occur in about 10% children with strep throat infection, and typically starts around the face and neck area and can spread to the rest of the body. It has a raised, rough "sand-paper" quality. The rash may start within 12 to 24 hours of the onset of fever and may last for several days.
Other features that are more likely to be seen in tonsillopharyngitis due to viral causes include the following:
Are strep throat symptoms different in children compared to adults?
Some of the general and constitutional symptoms of strep throat infection may vary quite a bit depending on the patient's age.
Infants primarily experience a thick "colorful" (yellow or green) drainage from the nose and possibly a low-grade fever, with fussiness, irritability, and a decrease in appetite.
Children aged one to three ("toddlers") may complain of a sore throat, trouble swallowing, poor appetite, crankiness, and swollen glands (lymph nodes) beneath the jaws.
Older children and adolescents generally look and feel awful with strep throat. They can have high fevers, very painful throats, often severe difficulty swallowing, and pus, which can sometimes be seen covering the tonsils.
Adults with strep throat may have milder symptoms, and in some cases the illness may be undetected. Symptoms vary; adults may also have severe pain and trouble swallowing.
When should I be concerned about a possible strep throat?
Parents should be concerned about a sore throat that does not improve after a sip of water after arising from sleep, or one that is accompanied by a headache, high fever, stomachache, vomiting, or severe tiredness. The presence of a red, somewhat rough-to-the-touch rash is also a concern, known as scarlet fever (but this is no more dangerous than strep throat without a rash).
An urgent call to the doctor's office or emergency room visit is appropriate, especially in a child who has extreme difficulty swallowing that causes drooling or difficulty breathing.
How is strep throat diagnosed?
During the doctor's physical examination, a throat culture might be taken by touching a soft cotton swab to the throat and tonsil area. Germs from the swab are smeared onto a special plate and sent to the laboratory for evaluation of strep or other bacteria. After 24-48 hours, the rapidly-growing strep germs can be identified if present in the sample. Throat culture is the gold standard in diagnosing strep throat infection.
A culture for strep throat may not be done as a screening test in an individual without any symptoms suggestive of strep throat. This is because bacteria may be present without causing an infection. A person may be a carrier of the bacteria but not infected.
Rapid strep test
Rapid strep tests (also called the Rapid Antigen Detection Test or RADT) are available that can give results in minutes. A sample from the back of the throat or tonsils is taken using a swab similar to the sample for culture. Using a RADT kit, the doctor can determine within a few minutes if strep is the likely cause of sore throat. This test is less precise than throat cultures. Therefore, if the health care practitioner has a high suspicion for strep throat, both tests (RADT and throat culture) may be performed, and treatment should be started as soon as possible even if the rapid test is negative for strep while waiting for the definitive culture results.
Taking any "self prescribed" antibiotic prior to seeing the doctor should be avoided because even a single dose of antibiotic can interfere with the culture results and the health care practitioner's ability to correctly diagnose and treat the infection.
Blood test for strep throat infection
Streptococcus infection can be detected by measuring the antibodies produced by the body against the bacteria. This is called the Anti-streptolysin O or ASO titer. This antibody may not be present in the blood for a few weeks after an infection, and therefore its measurement may not be accurate to detect an active or acute infection. ASO titers also may not be detectable if the person had been appropriately treated with antibiotics.
This test may be useful in detecting prior infections and evaluating a person with complications of strep throat infection such as rheumatic fever or glomerulonephritis (see below).
Who should be tested for strep throat?
There is not an easy system to decide who should be tested for strep throat. However, there are certain predictors that make the possibility of strep tonsillopharyngitis likely. These include:
Children and adolescents between the ages of five and 15
Illness occurring in the late fall, winter, or early spring months
Clinical evidence of acute pharyngitis:
redness and swelling in throat, white discharge on the tonsils
Some clinical studies suggest that if all of these points are present, then the likelihood of strep throat may be up to 85%. The doctor may decide if testing is necessary based on these or other clinical factors.
How is strep infection treated?
Because of potential significant complications (described below), if strep throat is detected, it must be treated adequately with antibiotics. It is important to take the full course of antibiotics as prescribed and not to stop the medication when symptoms resolve. Prematurely discontinuing antibiotics can result in the infection being inadequately treated, with potentially adverse consequences or relapse of the infection.
Streptococcus is highly responsive to penicillin and the cephalosporin antibiotics. Penicillin has shown good effectiveness, and it is reliable and cheap.
Oral penicillin V (Pen-Vee-K, Veetids) is the preferred oral form of penicillin for strep throat. The usual dose is 250 milligrams three times a day or 500 milligrams twice a day. A full 10 day course must be completed even though patients usually feel better only after two to three days.
Injectable penicillin G (Bicillin) is also very effective and may be used in individuals who may not reliably take 10 days of antibiotics orally. The drug may last in the body for up to 21 days and can therefore adequately treat the infection.
Other penicillin derivatives such as amoxicillin (Amoxil), amoxicillin-clavulanate (Augmentin), cloxacillin (Cloxapen, Tegopen), and dicloxacillin (Dynapen) are all adequate treatments for strep. They may be even slightly more effective than penicillin because of better absorption and greater potency.
Cephalosporin antibiotics are also a very effective in treating group A streptococcus. In some studies, they were found to be better than penicillin, and there is some suggestion that they may be the first choice antibiotic for this infection. For now, they remain a very good choice in patients with mild penicillin allergies.
Some examples of cephalosporin antibiotics used to treat strep throat are:
Other options are macrolides, such as erythromycin (E-Mycin, Eryc, Ery-Tab, PCE, Pediazole, Ilosone), azithromycin (Zithromax), and clarithromycin (Biaxin). These antibiotics have shown similar to superior effectiveness compared to penicillin for the treatment of group A streptococcus. Erythromycin is thought to be the optimum choice for people with severe penicillin allergy.
The current recommendations still list penicillin as the first choice for the treatment of group A streptococcus. Erythromycin is recommended as the first choice in penicillin-allergic individuals. First generation cephalosporins such as cephalexin and cefadroxil, are alternatives to erythromycin.
How can viral throat infection be treated?
For viral infections, generally no antibiotic is needed (unless the infection becomes complicated by a subsequent bacterial infection). Most viral infections can be expected to run a four-to-six day course. During this period, the child or other infected individuals can be treated with lots of fluids, rest, and "feel better" medicines that reduce pain and/or fever, such as acetaminophen (Tylenol, Tempra, Liquiprin, etc.) or ibuprofen (Motrin, Advil, etc.). It is important to note that these measures do not treat the viral infection and only provide some relief of the symptoms. These measures can also be helpful in treating the symptoms of bacterial throat infection, such as strep throat.
Are there any recommended strep throat remedies?
Recommended home remedies for sore throat and tonsillopharyngitis (both strep throat and non-strep throat) are easily available in most circumstances. These remedies are generally geared towards relieving symptoms of sore throat and should not replace antibiotics in cases of proven strep infection.
Saltwater gargle is an old therapy for sore throat symptom relief. Typically, ¼ to ½ teaspoon of salt is added to a cup (8 ounce) of warm water. Portions of the solution are used for each gargle. Gargling can be repeated a few times daily. Children younger than 8 years of age are not capable of gargling and this therapy should be avoided in this age group.
Hard candies can be used to treat sore throat symptoms. Sucking on a hard candy is as beneficial as some of the other listed therapies.
Lozenges (cough drops, troches, or pastilles) are also available for symptomatic relief of sore or dry throat. Cooling (Menthol), anesthetic (phenol or benzocaine), antiseptic, or anti-inflammatory agents may be used in these products to provide adequate symptom relief. The use of lozenges is not recommended for children under 4 years old.
Other home remedies for symptomatic relief of sore throat and strep throat include warm tea with honey, lemon tea, chicken soup, cold beverages, ice cream, and Popsicles. Honey should be avoided in children less than 1 year of age because of increased risk of botulinum toxicity and paralysis.
It cannot be overemphasized that despite these therapies, antibiotics are the most important treatment for adequately diagnosed strep throat because of the dreaded complications of untreated strep infection.
When should the tonsils be taken out?
Surgical removal of the tonsils is much less common today thanks to the present ability to rapidly and accurately diagnose strep infection, and thanks to the excellent antibiotics currently available. But occasionally, your doctor might suggest the need for surgical removal of the tonsils (tonsillectomy) if an individual:
is experiencing frequent episodes of tonsillitis (especially those caused by the strep bacteria),
has tonsils that are so large, even when the individual is well, that they cause not just "snoring" but significant obstruction or blockage of the airway during sleep (sleep apnea), or
develops an uncommon but serious deep-seated infection within and surrounding one or both of the tonsils, called a "peri-tonsillar abscess."
Why is it very important to detect and treat a strep throat?
Studies have shown that if treated within the first 48 hours of symptoms, the duration of the symptoms is reduced by one to two days. If untreated, the body will generally clear the infection within two to five days, and this is the usual course of the illness.
Another reason to treat strep infection early is that there is a 35% reduction in transmitting the disease by contact. There are reports that within 24 hours of starting antibiotics for strep throat such as penicillin, individuals become minimally contagious.
More importantly, there are many potential sequelae of untreated strep infection, as described in the following section.
What are the potential complications of untreated strep throat infection?
Possible complications of untreated or partially treated strep throat infection are:
meningitis (spread of infection to the lining of brain and spinal canal);
pneumonia (lung infection);
toxic shock syndrome (a rare but severe complication of strep pharyngitis, causing severe widespread infection and organ failure); and/or
abscess formation around the tonsils and behind the throat (peri-tonsillar abscess and retro-pharyngeal abscess).
Formation of an abscess behind the throat (retro-pharyngeal abscess) due to untreated or under-treated strep throat infection can lead to severe illness causing pain in throat and neck, difficulty swallowing, and potential respiratory compromise. These abscesses may need to be drained by an ear-nose-throat (ENT) specialist urgently, and hospitalization may be required.
There is also a condition called Pediatric Autoimmune Neuropsychiatric Disorder associated with group A Streptococcus infection (PANDAS). This is a theoretical and somewhat controversial condition linking group A strep infection with possible exacerbation of obsessive compulsive disorders or tic disorders (Tourette's syndrome) in children.
Acute rheumatic fever is a known and serious complication of strep throat. It is thought that if the strep throat infection is untreated or inadequately treated by antibiotics, the bacteria remain in the tonsils and promote a persistent immune response from the body. Certain strains of the bacteria are more likely to cause this response. At times, this ongoing immune response may trigger the immune system to mistakenly attack other organs in the body including the joints (causing inflammation of the joints or arthritis) and the heart valves. The involvement of heart valves can cause damage of the heart valves and potential heart failure.
Treatment with appropriate antibiotics, even if started several days after the resolution of the infection, may prevent acute rheumatic fever. Fortunately, it is now uncommon in the current antibiotic era.
Theoretically, a similar immune process to acute rheumatic fever may involve the kidneys and result in kidney inflammation called glomerulonephritis (or post-streptococcal glomerulonephritis). There is however, no evidence to support the use of antibiotics to prevent this condition. Children under the age of seven are at the highest risk of developing this condition after an episode of strep throat. This condition is less common and less severe than rheumatic fever. It typically resolves spontaneously after a few weeks and generally does not lead to permanent kidney damage.
Is there a vaccine for strep throat?
Currently, there are no vaccines available against group A streptococcus bacteria. There are currently concerns about whether a vaccine may initiate immune responses similar to those causing rheumatic fever and glomerulonephritis.
Can strep throat be prevented?
The important aspect of preventing strep throat infection is to prevent its spread to others. Simple steps can be taken in order to limit the spread of strep throat:
Covering mouth and nose when sneezing or coughing
Washing hands frequently
Washing dishes and utensils used by the infected individual frequently
Keeping dishes, utensils, and other household items used by the infected person separate from those used by other family members
Do not share food or drinks with the infected individual
Strep Throat At A Glance
Most throat infections are caused by viruses.
The symptoms of strep throat include fever, sore throat, and swollen lymph glands in the neck.
The diagnosis of strep throat is confirmed by a throat culture or rapid-strep test.
Strep throat is treated with antibiotics.
If left untreated, strep throat may cause heart and kidney problems.