"Ten children were unwell enough to require admission in the past week. There has also been an increase in the number of children presenting to the emergency department for respiratory illness, such as an upper respiratory tract infection or bronchiolitis. However, confirmation of an RSV diagnosis takes some time so it is difficult to accurately confirm numbers for those children."
Silk said Whanganui Hospital children's ward had dedicated isolation rooms, so staff were able to care for infectious children who were admitted.
"If children develop cold and flu-like symptoms, please keep them at home and away from school or day care," Silk said.
"If your child is unwell, especially if they are experiencing difficulty with breathing or feeding, we advise whānau to seek medical advice from your GP in the first instance.
"We ask that visitors are kept to a minimum in the children's ward and that healthy children do not visit due to the infectious nature of the illness."
ESR (Institute of Environmental Science and Research) data shows weekly visits to New Zealand's six main hospitals for RSV has more than doubled in the last week, from 204 to 538 presentations. Only 34 cases were recorded between April to September last year.
As the virus spreads many daycare centres around New Zealand are reporting large numbers of sick children, with some saying their classrooms are half empty.
In Whanganui, First Years Learning Centre owner/manager Katrina Culhane said they had experienced "a bit of a rough week" last week, with quite a few children absent.
"No one came back with that [RSV] diagnosis but they all had those symptoms," Culhane said.
"I think RSV may have reached Whanganui. We're not as badly hit as places like Auckland and Wellington though."
While they had experienced a lot of absences, Bright Beginnings manager Lorri Bishop said she didn't know if they were a result of RSV.
"We've been hit by a number of bugs, predominantly cold and flu," Bishop said.
"Last Monday we had 20 children absent across our two centres.
"Whether some of that was undiagnosed RSV, I don't know."
Regular communication with parents was key when dealing with threats such as RSV, Bishop said.
"We sent out a poster to all our parents on our private Facebook page today about it, and we've spoken to them about it too.
"Face to face communication is important, as are things like courtesy calls if their children aren't well, or sending another message saying 'actually, you need to come and get them'.
"We know our parents are under the pump, so it's a partnership we work on with them.
"Everyone needs to do their bit, but we can't get away from the common cold, that's a given."
Elsewhere, Love and Learn Care and Education owner Marie Butturini said the centre was under half of its capacity last week.
"We were down to really low numbers," Butturini said.
Like Bishop, Butturini said she wasn't sure if RSV was responsible.
"Either way, we've had massive illness through the centre.
"There have been kids in hospital with respiratory problems, with all of the symptoms as well.
"It's been tough on the families, especially for working families.
"We've also noticed that it's lasting longer. Generally, you'd have kids out for a couple of days, but this is wiping them out for a whole week."
Last week had brought the worst run of illness the centre had seen in its six years of operation, Butturini said.
"Obviously something is going around, so we try and be as vigilant as we can, and give the parents as much information as we can as well.
"We seem to have the majority of the kids back this week though, so that's good."
Starship Children's Hospital general paediatrician Professor Cameron Grant told Newstalk ZB's Heather Du Plessis-Allan that babies born in New Zealand last year didn't get exposed to RSV because of lockdown and our borders staying closed.
"Those babies are seeing RSV for the first time this year as are all the babies that are being born this year. So we have twice as many babies having their first infection, hence getting really sick with this infection," Grant said.
It is believed the virus came from Australia.
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.
• There are no medicines that cure a cold. Antibiotics only work against bacterial infections, not the viral infections that cause a cold.
• Symptoms can be treated with medicines such as painkillers, nose drops or sprays, cough syrups and drops, throat lozenges and decongestants.
• If you have Covid-like symptoms, please stay at home and get tested.
Source: Ministry of Health