Two sets of parents who lost their newborn babies to a common virus are speaking out about their heartbreaking stories to warn other parents.

Jessica Buchanan and her husband Angus shared how they lost their son Jack when he was just 11 days old.

The Sydney mother, who has two other children, wrote in the Facebook group Dad Minus One Tuesday about how her seemingly healthy son got sick and died from the Herpes Simplex Virus 1 (HSV-1).

She said that he was born via C-section with little fuss and the family spent a “non-eventful week” in the hospital before taking their baby home.

However, Jack became fussy and wouldn’t eat, so the worried parents took him back to the hospital to get checked out.

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“When we went into an isolated room in ICU I knew things were really bad. They hooked Jack up to every medication you could imagine. He had drips in his feet. They couldn’t regulate his body temperature,” Buchanan wrote.

“The hours that followed were harrowing. There was nothing we could do to help, just watch as the doctors and nurses did their thing. They were amazing and for that I will always be thankful,” she continued.

However, the doctors couldn’t save their precious boy.

“Jack put up the fight of his life but unfortunately at 10:10 a.m. on Monday, 21st Sep 2015, 11 days after he was born, our son grew his wings and left us,” the mom shared.

The hospital performed an autopsy on Jack to determine cause of death. That’s when they discovered the newborn had contracted HSV-1.

“Neither Angus or myself have ever had a cold sore in our lives. No one in our immediate families get them. Certainly, no one who visited had a cold sore. I learnt that you can shed the virus when you are getting a cold sore for the first time, but we weren’t sick…Did Jack catch it off a nurse? Did he catch it off me? ‘You can send yourself mad trying to figure it out,’ the head of ICU said,” Buchanan wrote.

According to the World Health Organization, an estimated 3.7 billion people under the age of 50, or 67 percent of the population, had HSV-1 infection in 2012. The virus can be transmitted from oral or skin surfaces that appear normal and show no symptoms, though active sores do pose the greatest risk for transmission.

Jeff Gober, a dad from Phoenix, Ariz., shared a similar experience on Facebook, which was published on Café Mom Monday.

Gober’s daughter Mallory also died when she was just days old after contracting the potentially deadly virus, even though she was “never in contact with a person who had an active cold sore.”

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“Mallory could not keep her hands out of her mouth and eyes and she was constantly sucking on her fingers, so it’s almost certain that the virus got onto her hands at some point. It is possible to be contagious even without an active cold sore,” Gober wrote.

The dad said he’s sharing his story because he wants others to be diligent about protecting their children. “If any good can come from her passing and prevent someone else from experiencing the heartache, then I would be remiss not to make an effort,” he wrote.

“If you have a new baby, or will be around a new baby, wash your hands. A lot. If anyone wants to hold your baby, make sure they wash their hands first. Then make them do it again. Be extra diligent about washing your hands around newborns. Statistically speaking, you’re probably infected with HSV-1 whether you know it or not,” Gober wrote.