Acute hepatitis outbreak swells to nearly 900 cases; global data shows ‘mixed picture’
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LONDON — An outbreak of acute, severe hepatitis of unknown etiology in children has grown to 894 cases across 33 countries, according to data presented during a media briefing at the International Liver Congress.
“As of June 20, we now have 894 probable cases reported in 33 countries in five WHO regions,” Philippa Easterbrook, MD, senior scientist at the Global HIV, Hepatitis and STI Programs at WHO headquarters in Geneva, told attendees. “Since the last WHO public communication on May 27, this represents 244 additional cases over a space of about a month. However, it’s important to remember that this includes both new cases as well as retrospectively identified cases.”
Easterbrook noted that more than half of these cases (n = 449) are from the European region, with the United Kingdom alone accounting for 262 cases — nearly 30% of the global total. The second highest reporting region are the Americas with 368 cases; as with the U.K., the United States harbors a disproportionate number of cases at 290, or 35% of the global total.
“Together the United States and the United Kingdom account for 65% of the global total cases,” she said. “The majority of cases — 75% — are among children less than five years of age. Forty-four children have required liver transplantation, and there have been 18 reported deaths. Fortunately, in both the European and United States data, there does appear to be a declining trajectory in terms of reports of new cases, which is a positive development.”
Early in the investigation, adenovirus along with past or current COVID-19 infection were the primary suspects “and that is still the case,” Easterbrook remarked, noting that these viruses are likely independent or collaborative causes that result in hepatitis.
“Adenovirus remains the most detected of all viral infections with a rate of detection of about 53% across Europe and bit higher in the U.K., but they are not in all cases,” she said. “There does seem to be a higher rate of detection in the younger age groups and in those developing severe disease, so perhaps there is some link to severity.”
In terms of current COVID infection, in both Europe and the U.S. rates of detection are approximately 10%, which is what researchers expect, given the rate of transmission in the general population around that time.
“Some of the emerging hypotheses are [whether this outbreak] represents a post-COVID phenomenon,” she said. “Is this a variant of the rare but recognized multisystem inflammatory syndrome condition in children? It often occurs 1 to 2 months after COVID-19, causing widespread organ damage, but it is rare, and the cases of hepatitis that have been reported don’t seem to fit those features.”
However, Easterbrook noted that early on researchers were able to rule out COVID-19 vaccination as a potential contributor. “The majority of children [in these cases] had not been vaccinated, particularly the younger age groups, consistent with the vaccination policy in place at the time,” she said. “The clear message is 85% were unvaccinated, which is why that cause was excluded.”
For Easterbrook, the steady growth in cases and a still unknown etiology have highlighted the importance of capturing consistent data from multiple countries.
“We are seeing a somewhat mixed picture globally, with two countries reporting the majority of cases in large numbers,” she said. “We are seeing differences in age distribution; we are seeing some differences in the rate of adenovirus detection and COVID-19. It’s a mixed picture, and we really need to have good quality data collected in a standardized way from other countries.”
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Easterbrook P. WHO & EASL media briefing on cases of acute hepatitis in children. Presented at: International Liver Congress; June 22-26, 2022; London (hybrid meeting).
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