As a result, Lakes District Health Board has announced it is restricting visitors to its children's, special care baby and intensive care units.
It came after 48 children visited the Rotorua Hospital emergency department with respiratory illnesses on Monday. On average, 120 patients visit the department each day.
Rotorua Hospital chief operating officer Alan Wilson said in order to prevent the virus from spreading it was necessary to implement visitor guidelines within certain parts of the hospital.
"We need to try to limit overall visitor numbers and would strongly encourage children who are not patients to be kept at home."
Under the new guidelines, both parents or primary caregivers can be present during the day, and just one parent or caregiver can stay overnight.
No other visitors, including siblings, are allowed.
Parents bringing sick children to the hospital are asked to seek support at home for other family members where possible.
"We are doing this to ensure that illness is not spread from our sick children in hospital onto their siblings, whānau and broader community.
"We ask our community to remember we are doing this to help ensure tamariki in our hospital and at home are safe."
Specific precautions will also be in place while at the hospital, Wilson said, including parents not being able to leave the room their child is in.
Bradley described RSV as a "really nasty and highly contagious" virus that affected but was not isolated to children.
"While it causes a fairly mild cold and maybe a mild chest infection in adults, young children and particularly babies can get really sick with it as it causes narrowing of the breathing tubes, which are already tiny in small babies."
Children could present with what starts as a cold and a runny nose but it would soon spread to the lungs, causing wheezing and difficulty breathing.
Ngongotahā Medical Centre general practitioner and Rotorua Area Primary Health Service Board co-chairwoman Dr Genevieve Matthews was asking parents to keep children home to stop the spread.
"We are seeing very large numbers of children in general practice and after hours with colds and flu-like symptoms, some of them serious.
"For those children with asthma, or other lung issues, viruses, including RSV, can cause a lot of harm."
Meanwhile, at Tauranga Hospital, four patients are in intensive care while another 29 children have been admitted to the paediatric ward in the past few days.
Bay of Plenty District Health Board clinical nurse specialist infection prevention and control Robyn Boyne told the Bay of Plenty Times on Tuesday that in the last four days, 29 children had been admitted to Tauranga Hospital.
"Two to the intensive care unit and nine others were seen in the emergency department.
"There were three adults admitted, including two to ICU and two others were seen in the emergency department."
Tips on how you can help prevent the spread of RSV:
• Avoid kissing your baby if you have cold symptoms
• Don't let anyone smoke around your baby
• Ask people to wash their hands before touching your baby
• Keep sick children home from daycare, kindergarten or school
• Practice regular hand-washing
• Cough/sneeze into your elbow
• Keep your distance from others when out in public
Symptoms include cough, fever, runny nose and headache.
The symptoms are much worse when the infection is severe and can include a high fever, wheezing, severe cough and trouble breathing.
Any children in the community with symptoms should be kept at home and not mix with other children in public places.
