Health authorities have warned to be alert for symptoms after the third NSW death from a potentially fatal disease.

A woman in her late teens was confirmed as the latest victim of meningococcal in NSW after cases have spiked in recent weeks.

The woman had been attending the Spilt Milk music festival in Canberra when she became unwell.

Meningitis Centre Australia confirmed in a social media post the girl had “tragically passed from meningococcal”.

It was the third death from meningococcal disease in NSW this year, after a man in his 40s died from the disease after attending Splendour in the Grass in July, and a man in his 20s died after contracting the disease in mid-November.

NSW residents are being warned to be alert to the symptoms, with 29 cases reported this year.

There has been a slight increase in cases in recent weeks, compared with the same period over the previous five years.

NSW Health said most are due to the meningococcal B strain of the infection.

Meningococcal can be fatal within hours if left untreated, and can take the lives of people who otherwise appear fit and healthy.

Although the disease is now uncommon due to vaccination, it can occur in people even if they have been vaccinated.

Children under five and 15 to 25-year-olds are at the greatest risk of contracting the infection.

Tweet from @MeningitisAust

Executive director of health protection NSW Jeremy McAnulty said early intervention could be lifesaving.

“Meningococcal disease symptoms can appear suddenly and become very serious very quickly,” he said.

“I urge everyone not to discount symptoms when they appear or assume it may be just a mild infection.

“If you suspect meningococcal disease, don’t wait for the rash – see a doctor immediately.”

Symptoms of a meningococcal infection include:

• severe, unexplained limb pain
• difficulty waking up
• high pitched crying in babies
• severe headache
• aversion to bright lights
• stiff neck
• a red-purple rash which doesn’t disappear when pressed with a glass.

The rash does not always occur, or may present late in the illness.

“If symptoms rapidly worsen, or if your child is very unwell, call triple zero or go straight to your nearest emergency department,” Dr McAnulty said.