But barely a week living in the world, and something suddenly changed. His Gold Coast mum recalls trying to rouse her seven-day-old son at 4am only to find he was reluctant to feed, he was lethargic and he had a temperature of 38C.
Two hours later, Alec still wasn’t feeding. Ms McDonald, 29, couldn’t make sense of it. Her two-year-old daughter Keeley had never behaved like this. She’d put Alec to bed the night before at 11pm and he was completely fine.
“I thought, ‘You should be starving. There’s something seriously wrong’,” Ms McDonald said.
She grabbed her husband, Scott, and they rushed their son to hospital, where they watched as his condition rapidly worsened.
He developed a scarlet red rash across his torso, became extremely irritable, would scream at the lightest of touches and wouldn’t eat unless forced. He also stopped breathing right before their eyes several times.
Ms McDonald said doctors were at first unable to explain Alec’s illness, and ran “every kind of test you can think of”, but the lack of answers left her terrified her boy would not survive.
“He went downhill so fast,” Ms McDonald said. “I actually thought I wasn’t going to bring him home from the hospital.”
Alec was transferred to intensive care and the next day, he had a diagnosis. He had the potentially deadly human parechovirus, which can cause serious brain and blood infections.
Medical experts have recently stepped up research into the virus after a series of spikes in cases in Australia. Many hundreds of infants have been hospitalised since 2013, the majority being younger than three months old.
It has been dubbed the 'red, hot, angry babies' virus due to its symptoms, which include a fever, irritability, a rash, extreme lethargy, diarrhoea and abnormal breathing. In the more severe cases, the virus can cause seizures, sepsis and meningitis with crippling long-term consequences.
But like most parents, Ms McDonald had never heard of it.
"It ravaged his body," she said. "I could barely lay a fingertip on him and he would scream and cry. Every time I changed his nappy it was like I was hurting him terribly. If I tried to pick him up to feed him he would scream in pain.
"I'd just held and cuddled my newborn baby for a whole week and now I couldn't touch him... It was heartbreaking not being able to comfort him."
She was told by doctors little was known about the virus, and there was no treatment for it. Alec would have to fight it all on his own.
"It was just a matter of managing his pain and keeping him comfortable," she said.
They also learned that the illness had caused viral meningitis, a brain inflammation which can have devastating long-term effects such as hearing loss and learning disabilities.
After almost a week in hospital, Alec was taken home where he would spend the rest of his weeks-long recovery.
The thing is, it's not an illness that necessarily has a clean ending. Ms McDonald now has to take six-month-old Alec to see his paediatrician regularly to ensure he is meeting all his milestones. So far, so good. But it's something she'll need to keep doing until he reaches school age and she says the uncertainty is unsettling.
She has since met other parents whose children have vision and hearing impairments, brain damage or cerebral palsy, as a direct result of the parechovirus.
"Not knowing whether there will be long-term effects on the rest of their life, that's the scariest thing for parents," she said.
Ms McDonald said she hoped medical testing to help stop the virus from spreading would someday be introduced.
"How can you prevent something you can't see? We did everything possible to eliminate illness from our house before Alec was born."
And this is something Australian scientists are now working hard to make happen.
Last month, a team of researchers announced a new study into the parechovirus after three outbreaks struck Australian babies in two-yearly cycles, the first being in 2013-14, then in 2015-16 and 2017-18.
It is feared a fourth outbreak will occur in 2019, and experts are determined to solve some of the many unanswered questions surrounding the disease - including why it has returned every two years.
Dr Cheryl Jones, a University of Melbourne professor and Royal Children's Hospital infectious diseases physician, told Mamamia there were about 300 hospitalisations around the country in the latest outbreak spanning from spring 2017 to early 2018.
Dr Jones said its pervasiveness in Australia was larger than overseas, and the increasing severity was of concern in part because many sick infants are being left with long-term issues such as brain damage, developmental delays and ongoing seizures.
There are currently no specific treatments or vaccines for the infection, and there is no routine testing.
It's also unknown why some babies only have very mild symptoms - at worse, some diahorrea - while for others the infection can result in hospitalisation or, in rare cases, death.
Most people who are infected, including adults, do not show symptoms but due to the contagious nature of the virus, they can still spread it on.
"We need to know why has it been so severe in Australia, why are we getting more cases, and what the genetics of the virus is," Dr Jones said.
She was much more research was needed to understand the virus.
"We're really trying to engage with families to ensure we better understand the risks if you get infected, and what the outcomes are, so we can get early intervention happening and make sure we're following all babies who need to be," Dr Jones said.
For now, it's hoped there will be greater awareness among both parents and doctors particularly in the spring-summer outbreak period. And it's something Ms McDonald, too, dearly wants in order to protect other babies from going through what Alec did.
"I'm here hoping we won't have to keep dealing with this for the rest of Alec's life."
For more information about the parechovirus research being conducted by the Australian Partnership for Preparedness Research on Infectious Disease Emergencies, please click here.