A young mother is warning others not to kiss infants after her son contracted a potentially deadly infection from family and friends doing just that.

Zoe McGlade, 22, from Dublin, Ireland, took to Facebook in late December after her baby son, Koby, was hospitalized after developing respiratory syncytial virus (RSV), a virus that typically causes mild, cold-like symptoms but can be potentially serious in infants and older adults.

MOM'S RSV WARNING AFTER INFANT SON'S HOSPITALIZATION: 'DON'T BE SELFISH'

“Can I just stress to everyone that when a mom/dad tells you not to kiss their baby or to wash your hands before holding them JUST DO WHAT [YOU’RE] ASKED instead of mocking or calling us ‘overprotective,'’’ she wrote in a Dec. 30 post, which had nearly 300 reactions and more than 200 shares as of early Wednesday. “We went from this video to the picture in a matter of HOURS and now my poor baby is in isolation with oxygen to help him breathe and feeding tubes down him.

“A little cough or runny nose that you might think is nothing can literally be DEADLY to a baby as small as my boy...we’re lucky we came to the hospital when we did. I can’t wait to have my smiley baby back with me, say a prayer for us please,” she added.

Speaking to the Irish Mirror, McGlade said she first noticed 4-month-old Koby was unwell when he developed a cough.

She took him to the doctor, who initially dismissed his symptoms. But the mother took her son back to the doctor when he failed to get any better. At that point, he was diagnosed with a chest infection and was given antibiotics.

But even after days on antibiotics, McGlade said she noticed that her son was not improving. She chose to take him to a local hospital a few days after Christmas, on Dec. 28.

“I watched helplessly as Koby was put on oxygen immediately. His oxygen levels had dipped to 71 and anything below 94 is dangerous. He was also severely dehydrated and his fontanelle was sunken,” she told the outlet. “He had developed the RSV which has spread quickly through his respiratory system and into his lungs.

“He was put in isolation and hooked up to all these machines and monitors. It was very scary for me and Koby’s dad Luke,” she added.

The doctor treating the young boy told McGlade that her son likely developed RSV over the holidays when he was being held and kissed by others.

“The doctor told me that if I had waited even a few more hours to bring Koby in, it could have been a very different situation,” she said, noting she and her partner typically ask others to wash their hands before holding Koby and not to kiss him. However, “we were mocked and told we were [being] over-protective,” she told the Irish Mirror.

The virus is also the most common cause of bronchiolitis and pneumonia in children younger than 1 in the U.S.

Symptoms can include a runny nose, decrease in appetite, coughing, sneezing, fever and wheezing. In young infants, symptoms may present as irritability, decreased activity, and breathing difficulties, according to the Centers for Disease Control and Prevention (CDC).

While healthy infants and adults infected with the virus typically do not need to be hospitalized, those with severe cases, especially infants younger than 6 months old, may need hospital care to address breathing issues or dehydration.

The virus can spread when an infected person coughs or sneezes, or if infected droplets from the cough or sneeze enter the eyes, nose or mouth, or if you touch a surface that has the virus on it. It can also be spread through direct contact with the virus, like kissing the face of a child, according to the CDC.

People infected with the virus are usually contagious for three to eight days, and infections in the U.S. typically occur in the fall, winter, and spring.

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“We went from having a healthy little boy to watching him in isolation with feeding tubes and oxygen to help him breathe,” she added. “A little cough or runny nose that you might think is nothing can literally be deadly to a baby and we definitely won’t be letting people near him again.”

Fox News' Alexandria Hein contributed to this report.