There's been a dramatic spike in the number of Wellington children in hospital with the dangerous disease rheumatic fever.
Wellington's Regional Public Health service has issued an alert to doctors, hospitals, pharmacies and Covid-19 testing centres, telling them to be on the look out and to swab any children at risk.
The disease can cause life-long heart damage, and shorten people's lives by decades.
There had been nine Wellington children in hospital with acute rheumatic fever this year, the public health service said in its alert.
Normally there would have been one or two.
Nationally there had been about a 25 percent increase (from 58 to 72) in the disease, the service said.
All the Wellington children were from Porirua or the Hutt Valley.
Porirua GP Bryan Betty said the Covid-19 lockdown could have exacerbated the problem, with the disease a complication of strep throat, often a consequence of overcrowded homes.
"There has been a lot of concern about access to general practice over the lockdown and there is no doubt this could have had a part to play in what happened here...but it may not be the whole story," he said.
Papakura GP and clinical leader of school based health service Mana Kidz, Rawiri Jansen, said the numbers were a worry.
A diagnosis was devastating, he said.
"They will be hospitalised for several months, they will have ongoing health needs. So in that initial period when a diagnosis is made and for several months afterwards, a family's life is turned upside down," Dr Jansen said.
The Auckland Regional Public Health Service was also worried.
In a report to Auckland DHB, it said rheumatic fever could increase as the economic fall-out from Covid-19 hit.
There needed to be a renewed push for more testing and better housing, it said.
Dr Betty said the disease had been on the decline but in the last year or two the government and DHBs had dropped the ball.
"It's really, really disappointing. There has been a huge amount of work that's gone on in general practice and frontline community medical services over the last decade....so this is incredibly frustrating...to see this happen again," he said.
But Auckland's Dr Jansen said community-based Covid-19 testing centres also needed to lift their game.
His health service had been telling them for weeks to test for strep throat - but not all had listened and at least one child had not been tested who was later found to have rheumatic fever.
Both doctors said while the immediate measures were needed there had to be a long term push to alleviate poverty and create better housing.
That was the only way to get on top of the disease that was rarely found anywhere else in the developed world.