Officials have warned cases of invasive Streptococcal A have risen sharply this year, a more deadly strain of the bug is circulating and it is thought to have claimed the lives of one in four of those infected.
Strep A normally causes sore throats but in some cases it can infect other parts of the body causing meningitis, pneumonia, sepsis and septic arthritis and other complications. One in five people die within a week, rising to between 40 and 50 per cent of those who suffer toxic shock syndrome, another possible complication of invasive Strep A.
In the letter Prof Brian Duerden, Inspector of Microbiology and Infection Control, said between November last year and February there have been over 500 cases, a 62 per cent increase on the same period in the previous year.
He said: "This is of particular concern as initial reports suggest a possible increase in the case fatality rate to around 25 per cent."
Cases are spread out and not found in clusters with the disease striking all ages but older people are at greatest risk, Prof Duerden said.
People who have skin lesions, have recently had chickenpox, had a child recently or have had a respiratory infection are at greater risk along with people suffering from long-term conditions such as heart disease, cancer, diabetes, alcoholism or have a weakened immune system.
Prof Duerden told GPs: "Suspected invasive group A Streptococcal cases should be assessed rapidly in hospital and treated promptly.
"Clinical deterioration in patients with iGAS can be very rapid. Early recognition of possible signs and symptoms of iGAS and prompt treatment may be life saving."
He listed symptoms as general malaise, high fever, severe muscle aches, unexplained diarrhoea and vomiting, dizziness, low blood pressure, confusion, localised muscle tenderness or severe pain out of proportion to external signs and a flat red rash over large areas of the body.
Previous strep throat infection should be considered and close contacts of confirmed cases should be given antibiotics if they have symptoms, the letter said.
The Health Protection Agency monitors invasive group A streptococcal infection which normally affects around 1,200 people each year.
Dr Robert George, from the Health Protection Agency, said: "Group A strep is a common bacterium found in the throat and on the skin and may be carried for long periods of time without causing any illness. The infections we are talking about here remain uncommon and are at the severe end of the spectrum.
"Invasive strep infections can be treated with antibiotics and clinicians have received a timely reminder of the signs and symptoms of this infection and how to treat it.
"The current increases we're seeing may be attributable to the natural cycle of the disease with some 'quiet' years followed by a year of high incidence.
"The HPA is monitoring the situation closely."