Group A strep infection can affect various organs and parts of the body, ranging in severity from mild, with symptoms like a sore throat, to life-threatening, with symptoms like organ failure and very high fever. The bacteria that causes group A strep infection is called group A streptococcus, sometimes referred to by the acronym GAS. It is often present in the human body, commonly on the skin or in the throat, without causing illness or disease. Group A streptococcus can cause various infections like sinusitis, strep throat, scarlet fever, and rheumatic fever that are usually treatable with antibiotics. The most severe forms of group A streptococcus infection are necrotizing fasciitis and streptococcal toxic shock syndrome (STSS) that have very high fatality rates.
Streptococcus bacteria are classified based on various properties of the bacterium, and there are several groups, including A, B, C, D, and G. Bacteria classified as group A have a particular kind of cell wall and also have specific virulence factors. The virulence factors of bacteria include how they evade and inhibit the immune system of the infected person.
Common types of group A strep infection include skin and throat infections such as cellulitis, tonsillitis, and strep throat. Group A strep bacteria can also infect the bloodstream or other parts of the body including: the joints, causing septic arthritis; the lungs, causing pneumonia; and the brain, causing meningitis. Symptoms of a group A strep infection vary depending on where the infection is located, but often include fever, soreness or pain, redness and swelling.
In the case of necrotizing fasciitis, the bacteria infects muscle, skin and fat tissue, causing a rapidly spreading infection that can be very difficult to treat, and is fatal in 60% of cases. The condition is usually caused by an infected cut or wound, and early symptoms include swelling, redness and extreme pain at the site of infection. Streptococcal toxic shock syndrome involves group A strep infection of several parts of the body at the same time, commonly causing low blood pressure and organ failure. It spreads rapidly, and 20% of those infected die.
Group A strep is usually spread through direct contact with an infected person. Groups at higher risk of contracting a group A strep infection include the elderly, intravenous drug users, those with diabetes, and those suffering from skin lesions, for example children with chickenpox. Good ways of avoiding group A strep infection include washing one's hands frequently and keeping cuts and other wounds clean.