Two days after Kasen Clark was born on July 21, his parents, Lindsay and Jeff, took their new, 5-pound-14-ounce son to their Arkansas City home.

The couple, who also have a 17-month-old daughter, began adjusting again to having a new baby in the house -- late-night feedings, more diaper changings and loving lullabies. But less than a week after going home, Lindsay says something wasn't right. 

Kasen was lethargic and had no interest in feeding. 

The Clarks rushed their son to the South Central Kansas Medical Center. From there, he was flown to Wesley Medical Center and finally to Children's Mercy Hospital in Kansas City. 

Soon after arriving in KC, Kasen went into cardiac arrest. Lindsay says hospital staff performed CPR for 45 minutes while hooking him up to an ECMO machine to pump and oxygenate his blood. 

That's where Kasen is today -- now four weeks old and fighting for his life. Dr. Brian Birnbaun said Kasen is now a candidate for heart transplant

 and awaiting a heart transplant. 

"We are currently waiting for him to get a Berlin heart until he can have a donor heart," Lindsay said on a GoFundMe page. "He is fighting hard and not giving up."

Staff at Children's Mercy told the Clarks their son had damage to his heart muscle which caused his heart muscle to die. He was diagnosed with enteroviral myocarditis.

Lindsay says doctors first suspected Kasen had a problem with one of his coronary arteries, before they were aware of the virus.

Lindsay says the virus attacked Kasen's heart muscle, causing the heart muscle to die.

While the Clarks wait painfully for answers and a glimmer of hope, they say Kasen is yawning, able to move his arms and legs, and even smiles at his parents.

"He's very ticklish on his toes."

Click here to donate to the family. 

For parents concerned about enterovirus, ABC News shares what you need to know to keep your child healthy:

What are the symptoms?

There are hundreds of respiratory viruses, so it is difficult to know when a child develops symptoms whether or not it is Enterovirus D68. The CDC advises parents to focus on severity of symptoms rather than whether a child has a particular virus.

Notably, Enterovirus D68 usually presents without a fever. The most common symptoms are a persistent cough and runny nose. Parents should seek medical attention if their child starts wheezing or has trouble breathing, especially if they have a history of asthma or other respiratory problems.

Rare symptoms might include weakness or paralysis in the arms, legs or facial muscles, though health authorities have not established a definitive link between these warning signs and the virus. Any child with these symptoms should be seen by a doctor as soon as possible.

How can I prevent my child from getting the virus?

Hand washing is the first line of defense against any illness, according to the CDC. Children should wash their hands frequently with soap and water for at least 20 seconds at a time.

But Dr. Daniel Feikin, the epidemiology branch chief in the Division of Viral Diseases at the CDC said there is really no way to contain this or any respiratory virus.

“There is no vaccine. There is not really a lot you can do to prevent circulation,” Feikin said. “You can try to prevent at an individual level, but you cannot really stop it at a population level.”

How does it spread?

Enterovirus is a respiratory illness spread by saliva and mucus. When someone infected by the virus coughs, sneezes or touches a surface, they leave their germs behind, Feikin said.

This is why regular hand washing –- and frequently wiping down surfaces with soap or bleach disinfectants –- may help keep the illness from spreading quickly.

How worried should parents be?

“It is scary when you hear about something like this,” said Feikin of the virus and neurological symptoms. “At this point there are no recommendations to not go about your daily business, similar to the way you would if it is the flu.”

Dr. Richard Besser added that most children don’t need to be tested for enterovirus infection.

“Even if they are positive, the treatment will be the same as for a cold,” he said.