Group A strep can travel via food, surgical instruments or mere coughs and handshakes. But since the microbes are less contagious than cold or flu viruses, stricken patients don’t pose a major threat to the people around them. The best preventive measures are simple ones, like covering food, washing hands and cleaning wounds.

A life-threatening infection begins when aggressive microbes penetrate a mucous membrane or take up residence in a skin lesion, such as a bruise or a chicken-pox blister. The bacteria then multiply rapidly, producing toxins in the process. For three days, the patient may suffer swollen lymph nodes, a rising fever and excruciating pain at the site of infection. Penicillin can stop the attack at this stage, but by day four, infected tissues start dying. Bacteria soon saturate the bloodstream, destroying muscles and organs and sending the body into shock. Death can follow within hours.

Though it can resemble the flu, an invasive strep infection usually feels worse, even in its early stages’ Health experts agree that an ache or a sore throat is no cause for panic. But they stress the importance of having infected wounds promptly examined and treated, and they urge anyone who develops a fever of more than 102 degrees to see a doctor quickly. Invasive strep is rare, but it’s also unforgiving.