The most populated US state confirmed its first batch of cases of the disease that has been spreading across the country, causing severe respiratory problems in infants and young children, according to the state’s chief health official.

Four children, ranging in age from 2 to 13 and all from Southern California, have confirmed cases of enterovirus D68 (EV-D68). One of the patients is from Ventura County; the others are from San Diego County.

According to the Centers for Disease Control and Prevention, from mid-August to September 18, 2014, a total of 153 people from 18 states were confirmed to have respiratory illness caused by EV-D68, which has forced dozens of children to be hospitalized.

Enteroviruses are a group of viruses made up of more than 100 different varieties of strains, and only a handful affect humans. EV-D68 is one of them.

The disease is of particular concern for children – especially those with respiratory problems, like asthma.

Enterovirus symptoms are similar to the common cold, however, the variant now reported in 18 US states has caused wheezing and difficulty in breathing.

“There will definitely be more. It’s just a matter of time. This will spread across the entire country,” Dr. Pia Pannaraj, an infectious diseases specialist at the Children’s Hospital Los Angeles, told KTLA.

Children who contract the virus may experience difficulty breathing and wheezing, particularly youngsters with asthma problems.

“These children start with what seems like a normal cold on the first day — runny nose, a little bit of cough – but by the second day, they can’t breathe at all. They come in and they need a tube to help them breathe,” Pannaraj said.

More cases are anticipated in the coming weeks.

“We are not surprised to find EV-D68 causing some illnesses in California given the apparent widespread nature of this virus in other parts of the country,” said Dr. Ron Chapman, director of the California Department of Public Health (CDPH).

Parents have been advised by CDPH to consult a doctor immediately if they have children who are experiencing breathing difficulties (wheezing, difficulty speaking or eating, belly pulling in with breaths, blueness around the lips).

There is no specific treatment for EV-D68 sufferers, nor is there a vaccine to prevent it.