The outbreak of sudden liver disease in nearly 200 children have no known connection, although a possible link with a virus that can cause colds is being investigated. At least one child died and several others have required liver transplants.

The Centers for Disease Control and Prevention said in a nationwide health alert last week that the first U.S. cases were identified in October in Alabama. Since then, four more cases were reported in that state.

THE SYMPTOMS

Previously healthy children are suddenly developing hepatitis, or liver inflammation often caused by viruses. Children aged 1 month to 16 years have been affected. Jaundice, diarrhea and abdominal pain are among reported symptoms. Doctors and researchers are trying to figure out why a virus that usually causes mild gastrointestinal symptoms could suddenly be causing severe hepatitis in some patients. In the meantime, health officials in Alabama are telling parents and pediatricians to be aware of the symptoms of hepatitis.

Symptoms of hepatitis, which is inflammation of the liver, include fever, fatigue, loss of appetite, dark urine and light-colored stools. Severe hepatitis can cause jaundice, which is a yellowing of the skin and the whites of the eyes. None of the children in the cluster of nine cases reported in Alabama had COVID-19 or the COVID-19 vaccine, said Dr. Karen Landers, chief medical officer for the Alabama Department of Public Health.

The nine patients treated at Children’s of Alabama had a wide range of illness. While two required liver transplants, some others were treated only for vomiting and diarrhea when testing revealed elevated liver enzymes. All nine patients are recovering well, Landers said.

THE DISEASE

Hepatitis is usually caused by one of several contagious hepatitis viruses that have not been found in the affected children. Sometimes the disease is mild and requires no specific treatment. But severe cases require hospitalization and can lead to liver failure.

THE CAUSE

Authorities are uncertain what is causing the outbreak. Nine children in the Alabama cluster tested positive for adenovirus. Some types of the virus can cause colds but authorities are also looking at a version that can cause digestive problems. It is unknown whether that virus is a cause or is somehow contributing to the outbreak.

LOCATIONS

Cases have been reported in at least a dozen countries, including Denmark, England, France, Ireland, Israel, Italy, the Netherlands, Norway, Scotland, Spain, and the United Kingdom. In the United States, cases have also occurred in Illinois and North Carolina.

The CDC says all physicians should be on the lookout for symptoms and report any suspected case of what’s called hepatitis of unknown origin.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content. The Oregonian/OregonLive’s sister site, al.com, also contributed to this report.