While New Jersey has yet to record a case of the mysterious hepatitis in children, state health officials are on the lookout as the string of severe liver infections grows throughout the U.S. and around the globe.

“At this time, the (New Jersey) Department of Health is not aware of any cases among children in New Jersey. We are monitoring for any reports of potential cases,” a spokeswoman for the state health department said in an email.

Roughly 30 cases of unexplained hepatitis have been reported across 10 U.S. states, and nearly 300 probable cases have been identified worldwide. Most of the patients live in the United Kingdom.

The cases have baffled experts. They could be linked to the adenovirus — a virus that can cause the common cold — but their origin remains unclear.

Here’s what you should know:

When did it begin?

In October and November, five children were admitted to an Alabama hospital with “severe hepatitis and adenovirus,” according to the Centers for Disease Control and Prevention. The CDC, along with Alabama’s state and local health departments, began an investigation.

More cases soon emerged throughout the country, in Europe and now Asia.

Hepatitis — inflammation of the liver — is a serious illness often caused by viruses and can be life-threatening.

In April, the CDC issued a nationwide health alert “to notify clinicians and public health authorities about a cluster of children identified with hepatitis and adenovirus infection — and to ask all physicians to be on the lookout for symptoms and to report any suspected cases of hepatitis of unknown origin to their local and state health departments.”

Where are the cases?

Worldwide, there have been nearly 300 probable cases “of acute hepatitis of unknown origin.” In the U.S., Alabama, California, Delaware, Georgia, Illinois, Louisiana, Minnesota, New York, North Carolina and Wisconsin have identified possible patients.

Belgium, Denmark, France, Indonesia, Ireland, Israel, Italy, the Netherlands, Norway, Romania, Spain and the United Kingdom have also seen cases, according to the World Health Organization.

How old are the kids?

They range from 1 month to 16 years old, the WHO says.

How dangerous is this hepatitis?

The infections have caused four deaths. At least 17 children have needed a liver transplant, and as many as 10% of cases could require one, according to the WHO.

What should parents look for?

Children have experienced fever, nausea, vomiting, diarrhea and abdominal pain. Many had jaundice — a yellowing of the skin or eyes — and were discovered to have abnormally high levels of liver enzymes.

What’s causing this?

The adenovirus is the chief suspect.

“Adenovirus has been detected in at least 74 cases … SARS-CoV-2 (the coronavirus) was identified in 20 cases of those that were tested,” the WHO says. “Furthermore, 19 were detected with a SARS-CoV-2 and adenovirus co-infection.”

But “while adenovirus is currently one hypothesis as the underlying cause, it does not fully explain the severity of the clinical picture,” the WHO added.

Even more curious, the virus has not been known to cause illness of this sort.

“Infection with adenovirus type 41, the implicated adenovirus type, has not previously been linked to such a clinical presentation,” WHO said.

What’s an adenovirus?

Adenoviruses are common viruses that cause a range of illness, according to the CDC. Cold-like symptoms, fever, sore throat, bronchitis, pneumonia, diarrhea and conjunctivitis can result from an adenovirus infection.

The virus usually spreads through respiratory droplets or contact with infected surfaces.