When Charlie and Makayla Hardin's infant son Moxxon began to experience symptoms like a runny nose and cough, they thought he had a typical cold.
The Hardins, of Amarillo, Texas, did not expect Moxxon, the youngest of their four children, to be diagnosed with RSV (respiratory syncytial virus), a respiratory virus that could be dangerous to young children, cases of which typically spike in the United States in the fall and winter, during flu season.
"RSV was never on my radar because when our oldest child had it, it was just treated and wasn’t a big deal," Charlie Hardin told "Good Morning America." "And then with it being in the summertime, no one really thought it was RSV."
Once Moxxon, now 1, was finally diagnosed with RSV, he was hospitalized for five days and came close to being intubated due to his low oxygen levels, according to the Hardins.
He is now home and recovering well and the Hardins say they now know that his case is part of a spike in RSV cases across several states in the southern U.S.
"While we were in the hospital, I talked with a few friends of mine who have kids around the same ages as our kids, and they told me that their pediatricians had all told them that there’s a ton of RSV cases going around," said Charlie Hardin, noting that he and his wife wished they had known earlier so Moxxon could have potentially been diagnosed faster. "I hadn’t heard anything about it."
MORE: How to protect infants from dangerous viral infectionThe Centers for Disease Control and Prevention issued a health advisory earlier this month due to a seasonally unusual increase in the spread of RSV, especially in the South.
"Due to this increased activity, CDC encourages broader testing for RSV among patients presenting with acute respiratory illness who test negative for SARS-CoV-2, the virus that causes COVID-19," the CDC wrote in the health advisory.
Jacie Patton, a mother of two in Missouri, said that although she was aware cases of RSV were on the rise in the state, it still took nearly two weeks for her 4-month-old daughter Teagan to be diagnosed with the virus.
"They said she was to the point where if she had gone any longer it would have been a different story," Patton said of Teagan, who spent two nights hospitalized. "I wish I wouldn’t have waited that long [to take her to the hospital], but at the same time I didn’t know."
In Teagan's case, though she tested positive for RSV early on, she was sent home to recover from the virus on her own. After several days of seeing her suffer, Patton said she trusted her mother's instinct and took her to the emergency room of a local children's hospital.
"She wasn’t eating and she was coughing to the point she would throw up," recalled Patton. "Her diaper was completely dry and when she cried there were no tears coming out of her eyes because she was so dehydrated."
Adding her advice to parents, Patton said: "If you know something is wrong and you just don’t know what it is, just stick with your gut."
RSV infections are the most common cause of bronchitis and pneumonia in kids under the age of 1 in the U.S., according to the CDC.
Why the number of cases of RSV is on the rise now, during the warmer months of summer, likely has to do with the country's emergence from the coronavirus pandemic, according to Dr. William Linam, pediatric infectious disease doctor at Children's Hospital of Atlanta.
"As we’ve lifted restrictions -- less masking, more businesses open and more people out and about and interacting -- we’ve seen a spike in RSV cases," said Linam, noting the U.S. is following the pattern experienced by Australia, which also saw a late spike in RSV cases as pandemic restrictions were lifted.
RSV is a contagious virus that can spread from virus droplets transferred from an infected person's cough or sneeze, from direct contact with the virus, like kissing the face of a child with RSV, and from touching surfaces, like tables, doorknobs and crib rails, that have the virus on it, according to the CDC.
People infected with RSV are usually contagious for three to eight days, but some infants can continue to spread the virus even after they stop showing symptoms, for as long as four weeks, according to the CDC.
Among children, premature infants and young children with weakened immune systems or congenital heart or chronic lung disease are the most vulnerable to complications from RSV.
"Pretty much all kids have gotten RSV at least once by the time they turn two, but it’s really younger kids, especially those under 6 months of age, who can really have trouble with RSV and sometimes end up in the hospital," said Linam. "That’s where we want to get the word out, for families with young children or children with medical conditions, making sure they’re aware this is going on."
MORE: Mom's Facebook post warns others to not kiss babies after her infant contracts RSVParents should be alerted to symptoms including difficulty breathing, dehydration and not eating, according to Linam.
"Not making a wet diaper in over eight hours is often a good marker that a child is dehydrated and a good reason to seek medical care," he said. "Sometimes kids under 6 months of age can have pauses when they’re breathing, and that's something to get medical attention for right away."
In the case of the Hardins' son Moxxon, he experienced difficulty breathing to the point where they noticed a slight change in the color of his lips.
"His lips would turn this really light shade of purple that wasn’t severe but it was enough different from his normal pink," said Makayla Hardin. "I would tell parents the [color of the] lips and the fingers and the toes are the biggest thing to look out for because everything else looks like it could be a cold, like a runny nose and fever."
Parents can help protect their kids from RSV by continuing to follow as much as possible the three W's of the pandemic: wear a mask, wash your hands and watch your distance, according to Linam.
"I don’t think people need to necessarily lock down like we were doing in the early parts of the pandemic, but there’s a balance in there, especially if you have a young infant or a higher-risk child," he said. "If you have a child who has significant underlying health conditions, you probably need to sort of maintain some of those precautions you were following during the worst of the pandemic, like continuing to wear masks more when you’re in enclosed spaces, being diligent about keeping hand sanitizer with you and using it a lot and avoiding crowds."
Linam said parents should be prepared for more contagious viruses like RSV to spread as people resume activities post-pandemic.
"As precautions start to lift, we’ll start to see more of these viruses circulate, so my hope is that we'll find that nice balance of continuing some of these strategies to keep [kids] safe," added Linam.