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Identifying infection: strep throat and scarlet fever

I'm a little confused about the difference between strep throat and scarlet fever. I thought strep was pretty common and that scarlet fever was no longer something to be concerned about. What's the difference?

While strep throat might appear to be more of a concern, scarlet fever is still with us and should be taken seriously. The two infections are caused by strains of streptococcal bacteria.

"Scarlet fever is still common, particularly during flu epidemics or cases of widespread upper respiratory viral infections," says Larry Culpepper, M.D., chairman of the Department of Family Medicine at Boston University School of Medicine and Boston Medical Center. "Often, people may think it's just the flu and it will pass, but that's not the case," he says.

Strep throat does have some classic signs and symptoms, including a sore, red throat (sometimes covered with white patches), fever, and swollen lymph glands in the neck; however, not everyone will exhibit these symptoms. Scarlet fever may cause a sore throat and fever, but it is also marked by a distinct rash, which frequently begins on the neck and upper chest. The rash spreads rapidly, and the face may also appear reddened and flushed.

According to Culpepper, it's very important to treat strep throat and strep-induced infections like scarlet fever as soon as possible. Left untreated, the infection can lead to other, more serious complications, including glomerulonephritis, an interruption in the kidney's ability to filter out waste products, and rheumatic fever, which can cause pain, inflammation, and swelling of the larger joints. Rheumatic fever also has the potential to cause damage to the heart muscle and heart valves. The central nervous system may also be affected, causing Sydenham's chorea, a disorder that results in rapid jerking motions and loss of limb control.

In order to prevent any of these complications, it's necessary to treat strep infections with antibiotics. Unlike some bacterial infections that are growing more resistant to antibiotics, strep can still be treated effectively with penicillin. "It's important to determine that you do have strep, as opposed to a viral infection," says Culpepper. "Taking antibiotics unnecessarily can help contribute to the development of resistant bacteria."

The standard method of diagnosing strep infection is a throat culture, which normally takes two to three days. However, several new, rapid tests can be done in the physician's office to help guide treatment. While such tests are generally quite accurate, on occasion the standard bacterial culture is still useful, because although it happens rarely, the three-day culture may identify a strep infection missed by a rapid test, or may identify another bacterial cause of the sore throat.

If you do have a strep infection and are prescribed an antibiotic, it's very important to finish the entire prescription as directed by your physician and pharmacist. Although you may begin to feel better after two or three days, the bacteria have not been completely eliminated. Taking all of the medication as prescribed also helps prevent promoting the development of antibiotic-resistant bacteria.

Finally, if you find that your family continually suffers from strep throat, scarlet fever, or other strep infections, you might want to look for another explanation. Some members of the family may be chronic carriers, even though they do not have symptoms. The symptomatic family member might be repeatedly infected. Culturing everyone in the household may be the necessary detective work. "Believe it or not," says Culpepper, "dogs can be chronic carriers of strep infections." A visit to the veterinarian can help identity if Spot is a strep carrier.

"Health Matters" is written in cooperation with staff members of Boston Medical Center. For more information on strep throat and scarlet fever or other health matters, call 617-638-6767.

23 February 2001
Boston University
Office of University Relations