The rapidness of the disease saw the teenager first arrive at Twizel Medical Centre before being sent through to Timaru Hospital.
She was transferred from Timaru Hospital to Christchurch Public Hospital on December 30, 2013 but by the end of the week her condition had deteriorated.
Miss Rushton's Facebook page has been inundated with messages.
"It can be very quick and in this case it was a great shock to the family and the hospital staff treating her," Dr Humphreys said.
The meningococcal disease is a bacterial infection that can strike anybody, at any time.
Dr Humphreys said it was important that people got treatment quickly if they had symptoms but not all cases developed all the symptoms.
"It can be very hard to diagnose with non-specific symptoms ... sometimes the cluster of symptoms are not together," he said.
One in 10 people had meningococcal in their nasal passage and were "perfectly fine" but occasionally the bacterium moved out and got into the blood stream.
"It is terribly difficult to diagnose but it is better to check it out (with your GP) especially if you're worried about it."
He said vaccination was important especially with institutionalised people such as university students who given their living arrangements had a higher rate of transmission if an outbreak occurred.
The treatment would give them protection from several different strains of the disease.
It is understood Miss Rushton was vaccinated with meningococcal B vaccine as a child so it was suspected to be one of the other strains.
"This was a terrible tragedy but it doesn't happen very often, it's an unusual event."
Miss Rushton's funeral will be held tomorrow at Holy Name Church in Ashburton.
Meningococcal Facts:
• Meningococcal Disease is a serious bacterial infection, with around 100 confirmed or probable cases a year.
• The bacteria spreads through secretions from the nose or throat, such as coughing or sneezing.
• Meningococcal disease can be difficult to diagnose because it can look like other illnesses. It can spread very quickly.
• The symptoms may include high fever, headache, vomiting or (in infants) refusal of feeds, sleepiness, a stiff neck and dislike of or sensitivity to bright lights, joint and muscle pains and a rash.
• It can be treated with antibiotics but early treatment is important.
• If you or someone in your household has these symptoms call your doctor straight away.
(Source: Ministry of Health)