Severe inflammation of the liver (hepatitis) has recently been reported in previously healthy children. From April 21 there was 169 confirmed cases of “acute hepatitis of unknown origin” in children in 12 countries, with the vast majority of cases (114) occurring in the UK. Many of the children are under ten years old.
What has been of great concern to health professionals reporting these cases is the severity of the disease in these young, otherwise healthy children. Seventeen have required liver transplants and one child has died of liver failure.
The number of transplants is far higher than in comparable periods of previous years. While acute hepatitis in children is not unheard of, these latest figures are unprecedented and only partially explained.
One suspect is an adenovirus infection. According to the UK Health Security Agency, adenovirus was the most common pathogen found 40 out of 53 confirmed cases tested in the UK. The agency said that “research is increasingly suggesting that the rise in severe cases of hepatitis may be linked to adenovirus infection, but other causes are still being actively investigated.”
Adenoviruses are a large group of viruses that can infect a wide variety of animals and humans. They get their name from the tissue from which they were originally isolated: the adenoids (tonsils).
Adenoviruses have at least seven different types, and within those types there are genetic variants, just like we see with coronaviruses and other viruses. In this case, they are called adenovirus subtypes instead of variants.
Adenoviruses usually cause mild illnesses in humans. Some species cause respiratory diseases such as croup in young children and babies. Others cause conjunctivitis and a third group causes gastroenteritis.
The subtype associated with the current acute outbreak of hepatitis in children is called adenovirus subtype 41, in which the virus is found at least 74 cases so far. Subtype 41 belongs to the adenovirus clustering typically associated with mild to moderate gastroenteritis; essentially a stomach virus with symptoms such as diarrhea, vomiting and abdominal pain.
For most children and adults with a healthy immune system, adenoviruses are just a nuisance, resulting in an illness that is expected to clear in a week or two. Viral hepatitis due to infection by adenoviruses has so far only been classified as a rare complication.
Due to the number of cases and the severity of the disease in children, scientists are urgently investigating the cause of the outbreak. At the beginning of the outbreak, epidemiologists were trying to identify contact links to these cases and, of course, to figure out what was causing the viral hepatitis. It quickly became clear that this was not just a small isolated cluster of cases.
data from the Scottish National Health Service found that none of these children lived in a recognizable geographic pattern (e.g., near an open water source), that the mean (median) age at hospital admission was four years old, and no other apparent characteristics such as ethnicity or gender were there have been found to be associated with the disease. Similar findings were reported by the US Centers for Disease Control and Prevention.
Because some of the COVID vaccines used adenoviruses, some people on social media wondered if the vaccines were the cause of the outbreak. However, none of the cases reported in the UK had received a COVID vaccine and the COVID vaccines that use adenovirus use an unrelated virus that cannot reproduce.
Questions that need to be answered
Researchers have yet to find a direct causal link between adenovirus 41 and these cases of hepatitis. Are there other aggravating factors that contribute to serious illness, such as B. a co-infection with another virus like the coronavirus?
Obtaining population samples (both adults and children) to get an idea of how prevalent adenovirus 41 is in these reporting areas compared to other areas with little to no incidence would help solidify the link. Scientists also need to discover the genetic makeup of the virus. Has it changed significantly from the reference information we have on it?
Understanding the immune response in these cases compared to other mild adenovirus infections will be crucial. Research into prevention (vaccination) and treatment options, such as antiviral drugs, must also begin.
Hopefully we’ll have some answers – and treatments – soon. In the meantime, parents should watch their children for hepatitis symptoms, including yellowing of the eyes and skin (jaundice), dark urine, pale stools, itchy skin, tiredness, and abdominal pain.