Cases of a potentially life-threatening infection linked to scarlet fever are rocketing in Yorkshire, latest figures show.
The region currently has the highest rates of invasive group A streptococcal (iGAS) disease in the country.
Already this year there have been almost double the expected number of cases of the infection, a more serious manifestation of the same bug which causes scarlet fever.
Up to a quarter of those suffering from iGAS disease will die from it.
Doctors have been warned about rare but potentially severe complications and told to carefully monitor patients who may be affected.
The country is currently in the grip of a scarlet fever outbreak, with high levels of the illness for the third winter running, particularly in Yorkshire.
The illness is caused by group A streptococci bacteria, which is often found on the skin or in the throat and causes other ailments including tonsillitis and ear infections.
But in the more serious disease - which usually affects vulnerable patients - the bacteria can penetrate deeper and cause illnesses like meningitis, sepsis, pneumonia and necrotising fasciitis, known as the ‘flesh-eating bug’.
A spokesman for Public Health England said: “Approximately 15 to 25 per cent of people who develop an iGAS infection will, unfortunately, die from it.
“However, this varies considerably depending on the individual’s age, type of infection, general health condition before the infection and the strain causing the infection.”
Scarlet fever - which mainly affects children under 10 - is highly contagious, but antibiotics are usually effective in treating it.
However, parents have been reminded that it is vital to see a GP quickly and to ensure children complete their course of medication.
The more serious iGAS infection mostly affects adults and those with other health conditions are especially at risk.
The spokesman added: “In less common cases, Group A streptococci can penetrate deeper inside the tissues and organs of the body, and become what’s known as an invasive infection.
“Invasive Group A streptococcal infections (known as iGAS) usually affect more vulnerable people, including babies, elderly people, people with diabetes, heart disease, HIV infection or cancer, intravenous drug users and people with weak immune systems.”
Latest figures show there have been 121 iGAS cases in Yorkshire and the Humber in the 2015/16 winter season, compared to an average of 65 for the previous five winters.
That equates to 2.3 cases per 100,000 people, the highest in the country.
Numbers are expected to peak over the next four weeks.
“Early recognition and prompt initiation of specific and supportive therapy for patients with iGAS infection can be lifesaving,” medics have been warned in a briefing by Public Health England.
“Close monitoring, rapid and decisive response to potential outbreaks and early treatment of scarlet fever remains essential, especially given the potential complications associated with GAS infections.”
Levels of scarlet fever have been high in the past two winters, with numbers already exceeding the record numbers seen last year.
Nationally there have been 6,157 cases this winter, compared with 5,061 and 2,416 for the same period in the last two winters.
Currently Yorkshire has the third highest rate in the country with 15.5 cases per 100,000 people.
A spokesman for Public Health England said: “Streptococcal infections range in severity from very mild throat infections to serious life-threatening illness.
“Most infections are unpleasant but don’t pose a serious risk to health, provided they are appropriately treated with antibiotics.
“Most people experiencing one of these minor GAS infections will make a full recovery, although there is a small risk the infections could spread further or lead to complications if left untreated.”
Dr Theresa Lamagni, PHE’s head of streptococcal infection surveillance, said that anyone diagnosed with scarlet fever should stay off school or work until at least 24 hours after the start of antibiotic treatment to avoid passing on the infection and everyone should practice good hand hygiene.
A spokesman for Public Health England said: “Streptococcal infections are any type of infection caused by the streptococcus group of bacteria. Streptococcal infections range in severity from very mild throat infections to serious life-threatening illness. Most streptococcal infections can be treated with antibiotics.”