"He was admitted and, the next day put on an ECMO [lung bypass] machine before being flown to Auckland Hospital in critical condition."
That was close to four weeks ago and Martin's condition remains the same. He is still in an induced coma to let his body fight the infection.
"Mat has gone through countless procedures, been given a lot of antibiotics and had surgery, but the infection is matching his stubbornness."
Rowling admitted she did not understand the medical side of Mat's illness but said there had been complications with the flu.
She said Martin's illness was the culmination of a pretty bad year for the family.
Read more:
• Influenza far from just a cold
"His brother Joel passed away last year which was really hard on him, and there have been one or two other things they have had to contend with. Despite being run down, he and Tessa have continued to be there for everyone else during this time.
"We do not know what the future holds but we do know Mat's recovery will take months, if not years. And even then we'll never have the Mat we know and love, the one who chases his kids around the place, back entirely."
The Martin family has been bombarded with messages of support and offers of help since news of the illness spread.
"This doesn't come as a surprise to anyone as both Mat and Tessa are always doing things for others."
Tessa, who, with the couple's two sons, has been beside her husband the entire time, was initially reluctant to accept help from others.
"Both she and Mat are proud people and Tessa didn't want this to be anyone else's burden. She said they'd just sell what they had if need be and start again from scratch," Rowling said.
Eventually giving Rowling the go-ahead to start a Givealittle page, although making it clear any money not used on expenses incurred while Martin was in hospital would be given to charity, the family had been humbled by the response.
"We've been blown away to see how much money has been donated in such a short time.
"Reading all the messages and seeing so many of his students contribute shows how much of an impact Mat has made on the world already. The same goes for all the people he has played sport alongside – especially social cricket."
Rowling said it was hard to put into context how sick her friend was when "he had just got the flu".
To donate go to https://givealittle.co.nz/cause/going-in-to-bat-for-mat