Waikato Hospital is urging people with winter maladies to stay away after being swamped.
"The winter patient wave has hit us as predicted," said Emergency Department clinical director John Bonning.
The sudden influx of patients has meant some people have waited up to five hours to see a doctor.
"We are extremely busy and looking to maximise staffing for times of high presentations. We would ask the public to remember that you should only come to ED in an emergency, and not to present out of office hours just because that is convenient to you, as out of hours is when we are at our busiest."
Bonning said the worst affected were the very young and the over 70s.
Radius medical centre practitioner Navin Rajan said that the past few weeks have been "quite stressful".
"Normally we see [around] 5000 patients a fortnight but recently we are seeing 3000 a week, most of those with flu, viral infections and upper respiratory illnesses."
The clinic had seen a large number of people with the flu and coughs and a huge increase in people seeking their immunisation status because of the measles fear, he said.
"It has caught us on the left foot this measles epidemic. [But] it's certainly raised the profile of vaccination.
"We've had to quarantine one staff member who has had the measles."
Waikato DHB weekly statistics show there have been 50 confirmed cases of influenza last week.
There have been 70 different strains of flu virus doing the rounds in New Zealand this winter so far, including the H1N1 swine flu strain - with 12 cases confirmed.
A Healthline spokesperson said calls about flu and cold symptoms throughout the Waikato region this week had hit 408 compared to two at same time last year.
Midland Health Network chief executive John Macaskill-Smith said colds and viral infections have been "clogging up the system".
"Big cold and viral demand hitting practices is putting big pressure on the system."
He said common colds - rather than the flu - were the culprit driving people to seek medical attention, and this was causing long wait times.
"There is a limited capacity in the health system. That's why the healthlines are so important."
He encouraged people to get immunised but to understand that it is a protection, not a guarantee. "The flu jab saves lives, but it doesn't stop colds."
Ngaruawahia GP Mike Slatter urged people with winter maladies to go to Anglesea Clinic to ease the pressure on hospitals.
"Anglesea is kind of the safety valve in the system," he said.
Slatter said his clinic had been busy, particularly with flu and measles immunisations.
"It just takes one case of measles to drift into the community [and it will spread]."
Hundreds of people are staying away from workplaces and schools in droves.
And some of the illnesses being reported appear to have more severe and long lasting symptoms than in previous years, according to readers posting comments on the Waikato Times Facebook page.
Long waits to see GPs and nurses appears common in Hamilton and the wider Waikato.
Donalda Dalgity took her daughter, with suspected tonsillitis, to five different clinics before giving up. She
was successful the next day.
"I can see why people just go to Waikato Hospital when you can't get to see a GP anywhere unless [it's] an emergency."
Truck driver Mike Ward was hit hard for over a month with "superflu" symptoms.
He said he woke up one night in a sweat and found his temperature was 40 degrees.
He went to hospital and was seen after seven minutes waiting.
He spent the night hooked up to intravenous fluids.
"They treated me pretty well," he said.
Waikato Hospital's assistant group manager of hospital operations Kevin Harris is planning for things to get busier as the winter progresses.
"Waikato Hospital staff make detailed plans regarding the number of beds open at any one time over the busy winter period."
Medical officer of health for Waikato DHB Felicity Dumble said there was a rising demand for immunisations, particularly for MMR (measles, mumps and rubella) and GPs are holding special services to get these done.
There are currently 84 confirmed cases but that number will be updated by the Waikato DHB last week.
"We're encouraging the public to be proactive and putting in a lot of effort into getting parents to take action if their (kids) need to have vaccines.
"[Vaccines] offer protection for the individual - its great for the whole community."
A Hauraki Primary Health organisation spokesperson said it was concerned at low levels of immunisation among communities.
"Without 'herd immunity' the broader community is at risk of an increase in disease epidemics that New Zealand has been able to control through its immunisation programmes."
- Waikato Times