Throat Infection Cause
Sore Throat and Strep Throat
Causes, Diagnosis, and Treatment
Strep throat (streptococcal pharyngitis) is an infection on the back of the throat caused by a particular type of bacteria (group A streptococci). Strep throat is more common in children, but most sore throats are not due to strep. Most children and the vast majority of adults with sore throat do not need to take antibiotics for a sore throat. If a person does have strep throat, taking antibiotics can make them feel better sooner and prevent the spread of strep.
Main Points
Strep throat behaves differently in children and adults. There is some overlap for teenagers. Children under 3 years old are very unlikely to get strep throat.Children
- At most, 35% of children with a sore throat will have strep throat.
- Not all children who have a sore throat need to have a strep test, but all children should have a strep test before they get antibiotics.
- Only about 10% of adults with sore throat will have strep throat.
- Based on signs and symptoms, most adults do not need a strep test and most adults should not get antibiotics.
Adults and Children
- The antibiotic of choice to treat strep throat in adults is penicillin. For children, the antibiotics of choice are penicillin or amoxicillin. Penicillin is well tolerated and the bacteria that cause strep throat are never resistant to penicillin. Strep can be resistant to "newer, stronger" antibiotics.
Symptoms of Strep Throat
Strep throat classically causes the sudden onset of sore throat and fever. Strep throat causes a red throat with pus on the tonsils or the back of the throat (white patches or streaks called exudate). Strep throat causes tender "glands" (lymph nodes) in the front of the neck. The severity of the sore throat does not seem to make strep throat more or less likely. Strep throat typically does not cause symptoms of a more diffuse viral infection like cough, congestion, runny nose, hoarseness, or redness of the eyes. Unfortunately, most patients with strep throat do not have "classic" symptoms. Children have less specific symptoms than adults, including rash, headache, abdominal pain, and vomiting. Without treatment, the sore throat from strep throat generally lasts for 5 to 7 days. Risk Factors for Strep Throat
Strep throat is found on throat culture in about 10% of adult patients seeking care for sore throat. Strep throat is more common in children. The rate of strep throat can be as high as 35% in children with sore throat. Strep throat is also seasonal, with a peak in the winter and early spring. Because of increased exposure, strep throat is more common among healthcare and childcare workers, teachers, parents of young children, groups living in close quarters (like barracks or dormitories), and patients exposed to others with strep throat.Other Causes of Sore Throat
Strep throat is the only common cause of sore throat that should be treated with antibiotics. However, most sore throats are not caused by strep.Common Causes of Sore Throat
- Respiratory viruses: Respiratory viruses -- the cause of the common cold -- are by far the most common cause of sore throats in children and adults. Sore throats caused by respiratory viruses can cause pus on the back of the throat. Antibiotics do not help viruses. Patients likely to have a respiratory virus should not use antibiotics as any benefits are outweighed by the risks.
- Influenza: Influenza is a respiratory virus. When the influenza virus is circulating - generally between October and May in the northern hemisphere - influenza causes an illness that starts suddenly and is associated with high fever, cough, muscle aches, and sore throat.
- Acute infectious mononucleosis ("mono"): Mono may be the cause of pharyngitis in 1% to 6% of young adults. It only rarely is the cause of pharyngitis in adults older than 40 years of age. Patients with mono develop fatigue, fever, sore throat, and swollen glands over several days. Doctors may perform specific testing for mono in patients with the right history and symptoms. Most patients with mononucleosis return to full health within 3 months.
- Non-group A strep: Only group A streptococci cause the illness we usually call "strep throat." However, there are other types of streptococci, group C and group G, which can rarely cause sore throat. Group C and group G strep do not cause some of the complications caused by group A strep. Antibiotic therapy has not been clearly shown to help patients with group C and group G strep. However, occasionally patients with group C and group G streptococcal pharyngitis can have a sore throat that looks just like true group A strep throat. Penicillin may be indicated for patients with exudative pharyngitis, from whom group C and group G streptococci are isolated.
Rare Causes of Sore Throat
- Gonorrhea: Gonorrhea is a rare cause of sore throat - seen in less than 1% of adults with sore throat. Gonorrhea is most often obtained on the throat through oral sex. Gonorrhea of the throat most often has no symptoms. When patients with gonorrhea have sore throat, the severity is variable and the sore throat can last for a long time.
- Acute human immunodeficiency virus (HIV) infection: When people first contract HIV ("acute HIV"), they can have a diffuse flu-like illness. HIV is a rare cause of sore throat - less than 1% of patients with sore throat will have HIV. About 50% of people with acute HIV will have a sore throat. The sore throat from acute HIV is associated with headache, fever, muscle aches, loss of appetite, and rash.
- Diphtheria: Diphtheria is incredibly rare in the United States. As of March 2008, the last confirmed case was reported to the Centers for Disease Control and Prevention in 2003. Diphtheria is more common in developing countries. Diphtheria classically causes tiredness, low-grade fevers, a mild sore throat, and a thick coating on the throat.
Transmission and Prevention of Strep Throat
Group A streptococci are spread by droplets in the air and can be picked up off of contaminated surfaces. People with strep throat, if they are not treated with antibiotics, can shed strep for weeks, even after symptoms have resolved. Strep is passed from person to person by coughing or sneezing droplets into the air or touching surfaces from which other people will subsequently pick up the bacteria. Once a person has picked up group A strep, the time to symptoms start is 2 to 5 days. To prevent catching strep throat, you should avoid contact with people who are sick, wash your hands frequently, and avoid touching your hands and face.Evaluation
Clinical Criteria (Adults Only): Strange as it may sound, research has shown that a simple score your doctor can use, based on 4 findings, is useful to identify adults who are likely or not likely to have strep throat. The 4 findings are:- Fever: measured in the office or patient reported (a commonly used cutoff is 100.5F)
- Absence of cough
- Swelling or pus on the tonsils
- Tender glands at the front of the neck
Table 1. Centor Criteria for Strep Probability
| Points | Probability of Strep | CDC Recommendation | Post Rapid Test Probability of Strep | ||
| Positive Rapid Test | Negative Rapid Test | ||||
| 0 | 2% | No test, no antibiotic | 22% | < 1% | |
| 1 | 3% | No test, no antibiotic | 35% | < 1% | |
| 2 | 8% | Rapid test | 57% | 2% | |
| 3 | 19% | Rapid test | 79% | 4% | |
| 4 | 41% | Rapid test or antibiotics without a test | 92% | 12% | |
Children: Because the symptoms and signs of strep throat in children are not as reliable, these clinical criteria cannot be used.
- Rapid Strep Test: Rapid strep tests are done using a swab rubbed on the back of the throat and on both tonsils. Rapid strep tests identify chemicals unique to the bacteria that cause strep throat. Results should be available in minutes. The latest generation of rapid strep tests is very accurate. However, because throat culture can detect a few more cases of strep throat, some doctors perform a "back-up" culture on children who have a negative rapid strep test.
- Throat Culture: A throat culture is also done using a swab rubbed on the back of the throat. Results from throat cultures take at least 24 hours, and more commonly 48 hours, to come back.
Strep Carriers: Up to 20% of school age children may be asymptomatic carriers of strep. Rapid tests and cultures will show that carriers have strep throat even though strep is not actually causing symptoms. Thus, for carriers of strep throat, it is very easy to confuse inactive strep with a symptomatic viral illness with sore throat. Carriers are very unlikely to spread strep and are very unlikely to get complications from strep. For children and adults who might be carriers, it may be useful to get a throat culture when they have no symptoms.
Treatment
Antibiotics
There are 4 reasons for treating strep throat with antibiotics:- Reduce symptoms: Studies show that penicillin reduces the duration of symptoms by about 1 to 2 days. In most developed societies where strep throat and complications from strep throat are rare, the main reason to treat sore throat is to reduce symptoms.
- Prevent the spread of streptococci: It makes sense that treating strep throat with antibiotics will reduce the spread of strep to others. Patients with strep throat should take antibiotics for 24 hours before they return to school or work.
- Infectious complications: Complications from strep throat come in 2 types: infectious and non-infectious. The infectious complications include ear infections, sinus infections, and the formation of abscesses (pus pockets), usually around the tonsils. Although antibiotics decrease these complications, they are already very rare. Doctors would have to treat about 4000 patients with antibiotics to prevent 1 person from developing an infectious complication.
- Non-infectious complications: Two non-infectious complications of strep throat are acute rheumatic fever and post-streptococcal glomerulonephritis. Both of these conditions are caused by the immune system being activated by the bacteria that cause strep throat and then attacking our own bodies. In acute rheumatic fever the immune system attacks the joints, heart, nervous system (causing weakness and abnormal movements), and the skin. A common complication of acute rheumatic fever is damage to heart valves. Antibiotic treatment of streptococcal pharyngitis decreases the incidence of acute rheumatic fever. However, acute rheumatic fever is so rare today that doctors would have to treat 3000 to 4000 patients to prevent 1 case. In post-streptococcal glomerulonephritis, the immune system attacks the kidney and causes a change in the urine color and swelling throughout the body. There is no evidence that antibiotic treatment of streptococcal pharyngitis decreases the incidence of post-streptococcal glomerulonephritis. Post-streptococcal glomerulonephritis resolves by itself.
Special Cases: Clinicians should exercise caution when patients are at special risk from undiagnosed and untreated streptococcal infection, such as those with a history of acute rheumatic fever, patients with documented streptococcal exposure in the past week, patients who live in a community with a current strep epidemic, or those who are diabetic or otherwise immunocompromised. In such cases, the clinician should have a lower threshold for diagnosing and treating strep throat.
Close Contacts: Routine testing of close contacts of patients with strep throat is not necessary as long as the close contacts do not have symptoms.
Which Antibiotic?Penicillin is the antibiotic of choice to treat strep throat (Table 2). Group A streptococci are always sensitive to penicillin. Ten days of penicillin has a bacteriologic cure rate of 90%. The most easily administered preparation is penicillin VK. For children, amoxicillin is an acceptable alternative because of the availability of liquid formulations, but for adults amoxicillin is unnecessarily broad-spectrum. First-generation cephalosporins - antibiotics like cephalexin and cefadroxil - are acceptable alternatives for children and for patients who are only mildly allergic to penicillin (have not had severe reactions).
For patients who have severe allergies to penicillin or cephalosporins, erythromycin is the antibiotic of choice. In contrast to penicillin, strep can be resistant to macrolides - erythromycin, azithromycin, and clarithromycin - with rates ranging from 5% to as high as 50%. Guidelines discourage the use of macrolides. For patients who are allergic to penicillin and macrolides, clindamycin is a suitable alternative.
Table 2: Recommended Antibiotics for Strep Throat
|
| Antibiotic |
| Antibiotic of choice | Penicillin VK |
| Alternatives for children | Amoxicillin |
|
| Cephalexin |
|
| Cefadroxil |
| For penicillin-allergic patients | Erythromycin |
| Alternatives | Benzathine penicillin G injection |
|
| Cephalexin |
|
| Cefadroxil |
|
| Clindamycin |
Tonsillectomy
Tonsillectomy is the surgical removal of the tonsils. Some studies have shown that removal of the tonsils reduce the recurrence of strep throat. If a child or adult has 4 or more episodes of strep throat in a single year it might be reasonable to discuss tonsillectomy with your doctor.Non-Antibiotic Treatment
Everyone with sore throat - strep or not - can use pain relievers and fever reducers like acetaminophen or ibuprofen. There are many over-the-counter lozenges and sprays that can also help with the pain from a sore throat. Multi-ingredient cold remedies can be helpful for patients with viral illnesses, especially at night. Patients with nasal or chest congestion may benefit from decongestants such as pseudoephedrine. If using more than one over-the-counter medication, people need to be careful that they are not getting too much of any one ingredient.Many people also find it soothing to gargle salt water. Using a humidifier in the bedroom can soothe a sore throat as well. People with illnesses that include a sore throat should drink plenty of fluids, get rest, and avoid tobacco and alcohol. Unfortunately, zinc, Echinacea, and vitamin C have not been shown to be effective in the prevention or treatment of pharyngitis or the common cold.
Reasons to contact your doctor: If you have been diagnosed with strep throat, you should call your doctor if your symptoms have not improved after 14 days or if you develop a high fever (above 102F), confusion, difficulty breathing or swallowing, severe headache, pain in your face or forehead, severe fatigue, a rash, or chest pain.
More Information
- Centers for Disease Control and Prevention. Get Smart: Know When Antibiotics Work
- American College of Physicians/Centers for Disease Control and Prevention. Principles of Appropriate Antibiotic Use for Acute Pharyngitis in Adults (pdf)
References
- Linder JA, Chan JC, Bates DW. Evaluation and treatment of pharyngitis in primary care practice: the difference between guidelines is largely academic. Arch Intern Med. 2006;166(13):1374-1379.
- Linder JA, Bates DW, Lee GM, Finkelstein JA. Antibiotic treatment of children with sore throat. JAMA. 2005;294(18):2315-2322.
- Linder JA, Stafford RS. Antibiotic treatment of adults with sore throat by community primary care physicians: a national survey, 1989-1999. JAMA. 2001;286(10):1181-1186.
- Petersen I, Johnson AM, Islam A, Duckworth G, Livermore DM, Hayward AC. Protective effect of antibiotics against serious complications of common respiratory tract infections: retrospective cohort study with the UK General Practice Research Database. BMJ. 2007;335(7627):982.
- McIsaac WJ, Kellner JD, Aufricht P, Vanjaka A, Low DE. Empirical validation of guidelines for the management of pharyngitis in children and adults. JAMA. 2004;291(13):1587-1595.
- Centor RM, Dalton HP, Campbell MS, Lynch MR, Watlington AT, Garner BK. Rapid diagnosis of streptococcal pharyngitis in adult emergency room patients. J Gen Intern Med. 1986;1(4):248-251.
- Del Mar CB, Glasziou PP, Spinks AB. Antibiotics for sore throat. Update Software.
- Bisno AL, Gerber MA, Gwaltney JM, Jr., Kaplan EL, Schwartz RH. Practice guideline for the diagnosis and management of group A streptococcal pharyngitis. Clin Infect Dis. 2002;35(2):113-125.
- Cooper RJ, Hoffman JR, Bartlett JG, et al. Principles of appropriate antibiotic use for acute pharyngitis in adults: background. Ann Intern Med. 2001;134(6):509-517.
- Snow V, Mottur-Pilson C, Cooper RJ, Hoffman JR. Principles of appropriate antibiotic use for acute pharyngitis in adults. Ann Intern Med. 2001;134(6):506-508.
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