WASHINGTON, United States — The number of US children who have died from a mysterious form of hepatitis has risen to six and the condition has now been tied to 180 cases, health authorities announced Friday, as they continued to hunt for the cause.
The leading hypothesis remains that adenovirus 41 has a major role, but the Centers for Disease Control and Prevention (CDC) is looking at other factors too, such as whether prior infection with Covid-19 makes children more susceptible.
"I want to caution that it does take time to assess the evidence," the CDC's Jay Butler told reporters, stressing that the cases being probed aren't a sudden outbreak, but instead go back several months.
The CDC is still trying to confirm "whether this is a true increase in the number of cases of hepatitis in children, or an existing pattern that has now been revealed through the improvements in detecting cases," he said.
Several hundred such cases have been reported globally, with the highest number, 197, in Britain.
There is no evidence of any link to coronavirus vaccines, with the majority of cases among children under five-years-old and too young to have received the shot.
Another CDC scientist, Umesh Parashar, said the agency estimated every year there were 1,500 to 2,000 pediatric hospitalizations for hepatitis in children under ten for causes other than the hepatitis viruses A, B and C in the United States.
Even if adenovirus 41 were driving a small increase of around 100 hospitalizations over a year, it would be hard to pick up in the data, he said.
Butler said genetic sequencing has revealed multiple strains of adenovirus 41 have been detected in children with the hepatitis -- a finding that suggests it's not one single highly mutated "super" adenovirus at play.
Other theories include that the country might be experiencing a cluster of cases because Covid lockdowns had stopped the spread for a few years, or a lack of exposure to pathogens during lockdowns might have made children's immune systems more susceptible.
The UK Health Security Agency initially put forward another hypothesis that the presence of dogs in a household might play a role -- "but in talking with them further, they have not seen that hypothesis pan out," said Butler.
Adenoviruses are commonly spread by close personal contact, respiratory droplets and surfaces. There are more than 50 types of adenoviruses, which most commonly cause colds, but also several other diseases.
The CDC recommends preventive action such as hand washing, avoiding people who are sick, covering coughs and sneezes and avoiding touching one's eyes, nose or mouth.