An Auckland teenager fears she could have infected hundreds of people with mumps after three different doctors told her the huge lump on her neck was not because of the highly contagious virus.

Cailyn Selfe, 18, developed ulcers in her mouth the Monday before Christmas and noticed a large lump on her neck a few days later.

A friend had recently been diagnosed with mumps and she feared she had caught the virus so she went to an accident and emergency centre on Saturday.

She told them she had been in contact with someone with mumps but they diagnosed her with lymphadenitis, the enlargement of a lymph node usually because of infection, and told her it was not contagious.

So she went back to work at NorthWest Shopping Centre where she estimates she probably came into contact with about 500 people.

On the morning of Christmas Eve, Selfe's mum took her to Waitakere Hospital because she was still in pain and the lump was getting bigger. They did a blood test and two different doctors both told her it was lymphadenitis – but still no one took a swab of her throat.

She was told it was not mumps because it was her submandibular glands that were swollen, not the parotid gland.

They told her to wait a week and then come back if it was still swollen.

The Massey woman went to church on Christmas Eve and had Christmas lunch with family, including overseas guests.

By that evening Selfe, who had all her Measles, Mumps and Rubella vaccines, was in so much pain her mum took her to another accident and emergency centre where the doctor took one look and told her it was mumps.

A swab of her throat was taken and three days later the results confirmed she had the virus.

Given the outbreak, which has seen 1046 Aucklanders contract mumps so far this year, Selfe and her mother were both left astounded that no one took a swab of her throat earlier.

"I probably saw 1000 people because I thought I wasn't contagious. I'm just sad that I didn't know and I've probably infected them," Selfe said. "I just feel really bad."

Her advice to anyone who suspected they might have the virus was to insist doctors to do a swab so mumps could at least be ruled out.

Mother Adele Selfe agreed.

Cailyn Selfe is on the mend after getting mumps. (Photo / Supplied)

"I wouldn't think it was that hard [to diagnose] given there's a mumps epidemic. Even if it's not, I feel they should have done a check from the start."

She said she did not blame the doctors but wanted to raise awareness.

A Waitemata District Health Board spokesman said the staff at Waitakere Hospital made what they believed, at the time, to be a reasonable diagnosis.

"Given what we now know, the correct course would have been to diagnose mumps and recommend exclusion for five days. We are sorry this did not happen at the time," he said.

"Given there are more than 1000 people in Auckland this year with confirmed mumps, swabbing is no longer considered a useful way of making a diagnosis."

A spokeswoman for the Auckland Regional Public Health Service confirmed mumps was characterised by the swelling of a salivary gland, usually the parotid, but sometimes the sublingual, submaxillary or submandibular glands. Patients also often had a fever, she said.

During the current mumps epidemic the likelihood of salivary gland swelling being due to mumps had greatly increased and, in the latest advisory for health professionals, the service advised the virus be considered for all cases of salivary gland swelling, with or without fever, particularly if the person had contact with someone with mumps while they were infectious, she said.

The spokeswoman confirmed that because of the epidemic doctors were being advised a swab was not necessary if the patient had salivary gland swelling and the doctor did not think another diagnosis was likely. It recommended such instances be treated as probable cases and patients told they needed to stay at home, away from other people.

Mumps
• A person with mumps is most infectious from two days prior to salivary gland swelling until five days afterwards. 
• You risk catching mumps from an infectious person if you are non-immune and have been within 1 metre of an infectious person. 
• About 80 percent of the current mumps cases in Auckland were in people not fully vaccinated.
• Early symptoms of mumps include fever, headache, muscle aches, tiredness, and loss of appetite. 
• Men and adolescent boys can experience pain and swelling in their testicles, which in rare cases can result in infertility. Females can experience ovarian inflammation or an increased risk of miscarriage in the first three months if pregnant. In some people mumps can cause permanent hearing loss or inflammation of the brain and surrounding tissue.