U.K. mom Claire Henderson took to Facebook to warn other parents about an unlikely danger facing newborns -- a simple kiss from a well-meaning visitor. 
 
 Henderson posted pictures of her month-old daughter Brooke with visible cold sores on her face and around her lips. She says Brooke contracted herpes simplex virus 1 (HSV-1), a version of the herpes virus transmitted orally, after getting a kiss from a hospital visitor who did not know she was infected. And while a cold sore might not seem like a serious health problem in an adult, to a vulnerable newborn the infection can be serious. 
 
 "Please share this with every new mum and pregnant woman you know," she wrote on Facebook. "Before 3 months old, a baby cannot fight the herpes virus. If a baby contracts this it can cause liver and brain damage and lead to death." 
 
 Please share this with every new mum and pregnant woman you know... COLD SORES CAN BE FATAL FOR A BABY. Before 3 months... Posted by Claire Henderson on Tuesday, September 15, 2015 
 
 It is very uncommon for a baby to contract HSV-1 from this kind of contact, Dr. Harvey M. Friedman, professor of medicine at the Perelman School of Medicine at the University of Pennsylvania, wrote in an email to CBS News. 
 
 Most individuals contract HSV-1 as a child or an infant when the virus is being spread through skin-to-skin contact from an infected adult. Sores might not be visible on the skin of the infected person, according to the American Academy of Dermatology. 
 
 The other version of the virus, herpes simplex type 2 (HSV-2) is contracted mainly through through skin-to-skin sexual contact, and about 20 percent of all sexually active adults in the United States carry that virus. 
 
 Like Brooke's case, HSV-1 is generally passed on through kissing, sharing an object that comes into contact with a person's skin, like a razor, or simply touching someone else. 
 
 When a young child gets the infection, they generally experience fever, swollen and tender lymph glands, and mouth sores, according to nonprofit healthychildren.org. The sores will typically heal gradually over the course of a week or two. 
 
 What should a parent do to safeguard against their child contracting this virus? 
 
 "Avoid direct contact with baby if the visiting person or parent has a fever blister (cold sore = herpes) outbreak," Friedman wrote. "In the case with Brooke, the contact person did not know they were having an outbreak of herpes. In that case, there is virtually no way to prevent this rare event from happening." 
 
 As of Monday afternoon, Henderson's post has been shared more than 46,500 times on Facebook, and has made the rounds across other social media sites. 
 
 "I know this sounds like I am scaremongering," she wrote, "but if my friend had not told me about this my baby girl could have been seriously ill." 
 
 Henderson went on to write that baby Brooke is now fine and that all of her tests "came back clear." ||||| Claire Henderson, a new mom from Doncaster, England, posted the above shocking photos to Facebook on September 16. With them, she explained how a person with no visible signs of cold sores gave them to her baby Brooke by getting close to her. In babies, that virus can be fatal. 
 
 Henderson wrote: 
 
 Please share this with every new mum and pregnant woman you know... COLD SORES CAN BE FATAL FOR A BABY. Before 3 months old a baby cannot fight the herpes virus. If a baby contracts this it can cause liver and brain damage and lead to death. I know this sounds like I am scaremongering but if my friend had not told me about this my baby girl could have been very seriously ill. I noticed the signs early and got her to A&E, we have now been in hospital on a drip for 3 days and have got another 2 to go. She was VERY lucky, all her tests came back clear. The moral of the story is DO NOT let anyone kiss your newborns mouth, even if they don't look like they have a cold sore- 85% of the population carry the virus. And if someone had a cold sore ask them to stay away until it has gone. Everyone who I have spoken to had not heard of this before and so I felt it was important to share Brooke's story and raise awareness to stop anyone else going through what we have this week. 
 
 She's not wrong: According to the New York State Department of Health, the HSV-1 (oral herpes virus) manifests mildly in newborns at first. Some present with a fever and cold sores before becoming "very sick" with seizures. 
 
 NYU pediatrician Julie G. Capiola told Yahoo! Parenting it is imperative that parents "limit the number of people who visit and handle your baby for the first few months, and remind them not to kiss the baby's face, especially on the lips," in order to prevent cases like Brooke's from happening. 
 
 It's advised that you notify your doctor immediately when any of these symptoms become present, as the virus spreads quickly. 
 
 In 2008, ABC reported on the death of a newborn who had a cold sore for a day before it disappeared. Her parents thought nothing of it and only brought her to the hospital when she had a fever and rash a week later, where she was diagnosed with HSV-1 and died. 
 
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– The mother of a newborn in the UK is taking to Facebook to warn how easy it is to expose babies to herpes simplex virus 1 (HSV-1), which is the kind typically transmitted orally, and what caused her own infant to be put on a drip in the hospital as her body fought the infection. The source? A well-meaning hospital visitor who didn't even have visible cold sores and kissed baby Brooke on the lips. "Before 3 months old a baby cannot fight the herpes virus," Claire Henderson writes. "If a baby contracts this it can cause liver and brain damage and lead to death. I know this sounds like I am scaremongering, but if my friend had not told me about this my baby girl could have been very seriously ill." A doctor at the University of Pennsylvania tells CBS News that transmitting the virus this way is actually quite unusual, and that because "the contact person did not know they were having an outbreak of herpes ... there is virtually no way to prevent this rare event from happening." Still, one New York pediatrician tells Yahoo Parenting that parents can be proactive: "Limit the number of people who visit and handle your baby for the first few months, and remind them not to kiss the baby's face, especially on the lips." In 2008, a newborn with a cold sore died a week after symptoms disappeared, having been diagnosed with HSV-1, notes Cosmopolitan. As for Brooke, she was treated early, and "all her tests came back clear." (Here's another way babies are getting herpes.)