Is My Strep Throat Contagious?

Is Strep throat contagious? The quick answer is "yes, it is." Strep throat is a condition caused by a bacterial infection. This is caused by group A Streptococcus, a common bacteria for infections in the throat. In the most conservative terms, any time that a person has live bacteria of an infectious species, he or she is potentially contagious. Just being contagious does not necessarily mean that others will become infected. Contagious means that one has the potential to spread infection. Performing basic infection prevention measures will reduce the likelihood that infection will spread to others.

Strep throat can be diagnosed at a doctor's office using a swab and culture test. This basically means that the doctor or nurse will use a swab (most likely cotton) on a stick and gently rub it on the throat area. Some of the bacteria present will be transferred to the swab with this action. There are rapid indentification tests used in clinical labs; however, these can provide "false negatives" and should be followed up by a culture. A culture test is one where the technician will rub the swab from the patient over a special material called agar in a small dish called a Petri dish. The dish is covered with a lid and placed in a warm incubator for 24 to 48 hours. Once growth is seen on the agar, technicians can use tests to identify whether the bacteria growing are group A Streptococcus.

There is a common belief that Strep throat is no longer contagious after 24 hours. Strep throat will potentially spread as long as live bacteria still exist. A person will be contagious until the bacteria are eliminated. The 24-hour concept became popular because it is commonly believed that a person is no longer contagious 24 hours after starting antibiotic treatment. First, the person needs to be taking the antibiotics as directed for at least 24 hours to be effective. Second, the main reason that the person is, in fact, no longer contagious is that the bacteria are susceptible to the antibiotic treatments. Unlike some of the very difficult species that are starting to become common in hospitals (such as Methicillin-resistant Staphylococcus aureus, or MRSA), Streptococcus is not resistant to antibiotics in most cases. The vast majority of the infectious bacteria will be killed within the first 24 hours of antibiotic treatment. If the bacteria are no longer present, the person is no longer contagious. 

If a person has Strep throat, precautions should be taken to prevent infection in others. Basic infection prevention is simple, but frequently forgotten. Washing hands frequently and using sanitizers will eliminate some transfer of bacteria. Covering the mouth when coughing or sneezing will reduce the spread of bacteria in the air to other people or surfaces. It is important to remember that if one uses a hand to cover the mouth when coughing or sneezing, the bacteria will be on the hands. People need to remember to wash their hands and/or use sanitizers after coughing or sneezing. Common surfaces (for example door handles, faucets, sinks, and tubs) should be cleaned and disinfected regularly.

Because most of the bacteria will be eliminated within 24 hours of starting antibiotic treatment, the infected individual will begin to feel better. It is important to continue taking the antibiotics as prescribed for the full course ordered by the doctor. This will ensure that the bacteria are fully eliminated and will reduce the opportunity for resistant strains to become prevalent. The more resistant bacteria may survive the first dose or two of the antibiotic. Because of the low number of bacteria that are present, these may not contribute to continuing symptoms. Continuing the antibiotics through the full course will ensure that the more resistant bacteria are also eliminated with continued doses. Incomplete elimination of the more resistant bacteria allows the opportunity for the ones that have this resistance to spread and multiply, which will lead to problems in the future as the resistant strains become more common.