Newborns with burning temperatures and mums who'd just given birth were forced to wait on the floor at Middlemore Hospital for hours as the spread of winter viruses soars.

Experts warn hospital visits for flu-like illnesses are skyrocketing like never before due to babies and children having weaker immune systems from lockdown last year.

ESR (Institute of Environmental Science and Research) data shows weekly presentations at six main hospitals across the country for the most common flu-like illness, respiratory syncytial virus (RSV), has jumped from just five in mid-May to 204 last week.

ESR only recorded 34 RSV hospital presentations between April to September in total last year.

On Monday, Middlemore Hospital recorded its busiest day in history for paediatrics - the department which specialises in treating sick children.

There were 140 patients under 18-years-old who visited the emergency department (ED) on that day alone - and half of those turned up between 4pm and midnight, data from Counties Manukau District Health Board showed.

Usually, there are about 50 patients in that age bracket presenting to ED per day, Dr Vanessa Thornton, clinical director of Middlemore Hospital's ED, said.

She said ED was experiencing an "unprecedented demand" and a significant proportion of these presentations relate to winter viruses.

Kairo Brooks, eight-months-old, was struggling to breath and forced to wait on Middlemore Hospital's floor due a surge of winter sickness. Photo / Supplied

One mum described to the Weekend Herald seeing babies as young as 9-days-old with 41C temperatures waiting on the floor with mums who had just given birth.

Gabi Brooks, 23, said she was at Middlemore's Kidz First centre with her eight-month-old son Kairo who was struggling to breath and hadn't eaten in three days.

"I was really scared for him," Brooks said.

After being told to wait she joined about four other couples who were sitting on the floor with their babies and toddlers because there was nowhere else to sit, she said.

"The amount of people and children there, was through the door ... there were also kids on stretchers being bought in by ambulances who were just waiting."

Next to her was a mum with a tiny baby who became quite irritated, Brooks said.

"That mum got fed up and said to the nurse 'my baby's only nine days old, has a temperature of 41C ... I need help, I'm worried'."

Brooks and baby Kairo was finally seen three hours later and sent home later that night.

Middlemore Hospital has been at full stretch with patients hit by flu and colds, many of them youngsters. Photo / Michael Craig

Dr Sue Huang - a virologist who tracks flu-like illnesses - said since New Zealand opened our bubble to Australia there had been a sharp increase in the number of RSV hospital presentations.

"It's fascinating. The week we opened the bubble we had one presentation of RSV and it's been increasing ever since to last week we saw 204 presentations ... it's such a sharp exponential increase.

"I'm not surprised to hear Middlemore has been busy, I imagine Starship and others would have been to ... which is concerning," Huang said.

She said usually children experienced episodes of RSV in their first two years of life but last year there was a cohort of young babies who were never exposed to the virus due to lockdown and high-level safety measures like social distancing and hand-washing.

"So not only are you getting those children who have delayed exposure of RSV but also the group of babies born after them being exposed," Huang said.

Data from Counties Manukau DHB showed a total of 415 people presented to Middlemore Hospital's ED on Monday alone.

From comparison, the usual attendance equates to about 300 a day.

The spokesman for the DHB said last year Covid-19 precautions were front of mind for people and as such the number of colds going around were minimal.

"However, with greater face-to-face contact taking place this year we are seeing a significant upswing in these symptoms," he said.

Waitakere Hospital has also seen a "noticeable increase in paediatric emergency department presentations", with a DHB spokeswoman saying: "while not at record highs, presentations are higher than our usual seasonal fluctuations for this time of year."

Baby Kairo and mum Gabi Brooks waited on the floor. Photo / Supplied

DHBs say they needed the community to support hospitals by seeking the right care for their condition and leaving the ED free for those who need it most.

Most times a GP or family doctor can provide medical advice and prescriptions to manage acute injuries, illnesses and long-term conditions, they said.

Dr Mike Shepherd, the Auckland DHB's director of provider services, said Starship had also been seeing a record number of children brought to its emergency department and "we're asking the public for their help and patience".

"In response to the increased demand and to keep on top of waiting times, we're implementing our escalation plans, increasing staffing, bringing in help from other parts of the hospital and opening up extra inpatient beds.

"Our hard working staff are doing an exceptional job of safely caring for patients during this busy time."

Its message to parents was:

• If it's a serious or life-threatening emergency, please don't hesitate to call 111 or take your child to the emergency department.
• If you're unsure where you should go for care, call Healthline for FREE advice from a nurse on 0800 611 116.
• If you have an appointment at our hospitals or clinics, please attend the appointment as scheduled.

"Nothing is more important than getting help at the right time for your child, so if you need to come to Starship please do so," Shepherd said. "We're here if you need us. Our clinical team carefully assesses children who are waiting to ensure we see those with the most urgent needs first."

There were community clinics that provided free or low cost after hours care for children under 14 years old, adults over 65, and Community Service Card or High User Health Card holders.

What is RSV?

• Respiratory syncytial virus (RSV) causes infections of the lungs and respiratory tract.
• It's so common that most children have been infected with the virus by age 2, but it can also infect adults.
• Symptoms are usually mild and typically mimic a common cold but they cause a severe infection in babies - especially premature infants and elderly or those with weak immune systems.

Advice for self-management of colds

• Get plenty of rest.
• Drink lots of fluids such as water.
• Use a humidifier to increase air moisture, especially in your bedroom.
• Health advice also is available 24 hours a day by calling Healthline on 0800 611 116 with the service providing interpreters for non-English speakers.
• If you have Covid-like symptoms, please stay at home and get tested. See more information here.