What are the symptoms of hepatitis in children?
Dr. Huerta responds 4:43
(CNN) --
Cases of sudden and unexplained hepatitis in children have risen to 621 in 34 countries, the European Center for Disease Prevention and Control reported Thursday.
What is acute childhood hepatitis and how is it different from other types of hepatitis?
About half of those cases are recorded in just two countries: the United States and the United Kingdom.
This Thursday, investigators from both nations said they were working diligently to get answers.
One of his first tasks has been to try to decipher whether these cases of sudden and often severe liver damage in children represent a true increase from previous years.
The answer is that it depends on where you look.
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The UK has better data on its hepatitis cases than many other countries, because it only cares for children with liver disease in three national hospitals.
"Care for these children is very centralized," Diedre Kelly, a professor of pediatric hepatology at the University of Birmingham, UK, said at a news conference on Thursday organized by the Science Media Centre, an independent non-profit company.
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Kelly said that in a typical year, she sees about 20 children who suddenly develop hepatitis with no obvious cause for their liver inflammation.
This year, she has registered 176 such cases, an increase of almost 8 times.
But, this contrasts with European countries.
Kelly said he recently participated in a study that counted cases of childhood hepatitis in specialty liver centers across Europe, and they "reported absolutely no increase in the number of acute and severe hepatitis cases" or liver transplants. , compared to previous years.
Kelly says they're still trying to figure out what that means.
"Either Europe is behind us and still has to catch up, or it is a phenomenon that does not occur on the continent," she said.
In the United States, cases of hepatitis of unknown origin are not routinely reported to public health authorities.
What makes it difficult to know if the 180 cases being investigated imply an increase with respect to what doctors normally record.
What parents need to know about the rare cases of hepatitis in children that have increased in the US
In a CDC call to physicians Thursday, Amanda Ingram, an epidemiologist with the Alabama Department of Public Health, said state researchers have seen a statewide increase in emergency room admissions for children with hepatitis, jaundice, and liver failure for approximately one month, between November 21 and December 25, 2021.
Alabama was the first state to report a series of 9 cases of hepatitis of unknown origin in children.
However, the researchers do not have irrefutable proof.
But they have been able to come to some conclusions and narrow down the likely causes they are looking for.
In that sense, they point out that based on the questionnaires they collected from the cases, they have been able to rule out contact with dogs as a possible factor in the diseases so far, said Dr. Calum Semple, a pediatrician and professor of pediatrics and epidemiology at the University of Liverpool.
Many of the minors studied have dogs as pets or reported recent contact with these animals, so that possibility was initially on the list.
But, upon further study, the researchers say that was ruled out as a factor.
"We've looked very carefully at the case-control data, also from children with severe illness and children who don't, and there's no difference between them in terms of contacts with dogs," Semple said. .
CDC Releases Details on Hepatitis Cases of Unknown Cause in Children: Some Have Vomiting, Diarrhea, Respiratory Symptoms and Enlarged Liver
Although covid-19 has not been completely ruled out, it seems less and less likely that there is any link with hepatitis.
"I don't think we've completely ruled out Covid-19," Semple said.
"What I'm saying is I think Covid-19 is going down the list" of possibilities being tested, "and adenoviruses and viruses related to adenoviruses and the like are going up the list," he added.
However, this does not mean that the pandemic, with social distancing, masks and other changes in behavior, does not have something to do with all this.
It is quite possible that after almost two years of minimal exposure to infections, our immune systems behave differently.
UK researchers are examining T-cell responses in affected children to see if there is any unusual activation of these immune defenses in otherwise common infections.
About 70% of children in the UK and more than half of those in the US tested positive for adenovirus 41F in their blood.
Which makes the association hard to ignore.
However, the researchers are not sure that if they tested children of the same age and sex who did not have hepatitis they would find a different number of children with adenoviruses in their blood.
This is known as a case-control study.
And Will Irving, a professor of virology at the University of Nottingham in the UK, said the data could be coming soon.
"Adenovirus is the main possibility in this case, but we need more data to be convinced, at least for me," he said.
Outbreak of childhood hepatitis, what are the risks?
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Scientists are skeptical because adenovirus 41 is not usually a big player when it comes to virus infections.
It's not even in the top 10 adenoviruses that affect people each year, Ingram said.
"It's very hard to know if this is the cause, which we would instinctively believe is not, or if it was a trigger in the child who was susceptible for some other reason," Kelly added.
In the Alabama cases, the children with the most severe disease -- who ended up needing a liver transplant -- had the highest levels of adenovirus in their blood.
suggesting a dose-response relationship, something researchers look for when trying to understand whether two phenomena that are associated are at all related because one caused the other or simply by coincidence.
Interestingly, however, although many of the children test positive for adenovirus in their blood, samples of their destroyed liver tissue usually do not find any virus.
The researchers say they don't know what this means, but say it's unusual.
For example, when adenovirus 5 attacks the liver and you look at the liver cells under the microscope: "The liver cells are absolutely full of new adenovirus particles. So there is no doubt that the virus itself is infecting the hepatocytes and killing them." We still don't have that bond," Irving insisted.
So there are a couple of factors to consider, Irving said.
The virus may not be acting alone.
Or it may be triggering a detrimental immune reaction.
In Alabama, 75% of cases ––9 of 12 children currently identified with sudden hepatitis of unknown origin––had more than one virus detected at the time of their illness.
In addition to adenovirus 41, the children tested positive for viruses known to cause upper respiratory infections, including rhinovirus, enterovirus, respiratory syncytial virus (RSV), a type of coronavirus OC43, human metapneumovirus, and rotavirus, which commonly causes diarrhea.
None tested positive for a current COVID-19 infection.
What can be concluded from the detailed study of the Alabama children is that they were very sick.
Almost all had vomited, more than half had diarrhea and fever.
Nearly all had clear yellow eyes or a yellowish-orange tint to their skin, a symptom called jaundice.
At least in the UK, there appear to be no geographical or social links between the cases.
Which means that the children do not know each other, nor do they live in the same areas.
"It's actually a sporadic thing," says Kelly.
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If the hepatitis is being caused by an infection, or a group of infections, but it doesn't occur in children in the same area: what does that mean?
Irving, the virologist, thinks that could mean that many, many children and perhaps adults are infected as well.
But for most, these infections do not lead to serious liver problems.
"Which leads us to wonder what's so special about these kids" who are diagnosed with liver problems, Irving said.
To do this, researchers are turning to genetics to unravel the mystery behind these cases.
There are already several projects underway to study the genetic traits of affected minors and their parents, to see if they had any unrecognized risk factors for their liver problems.
Although the puzzle of these cases is fascinating, the researchers say they try to keep the affected families at the center of their work.
"We must not forget that there are 170 families [in the UK] who are very distressed by this mysterious disease that caused so much trouble for their children, and getting a liver transplant is a life-changing event," Semple said.
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