Live at ECCMID: Day 1

We’re here in Copenhagen, Denmark, for the 33rd European Congress of Clinical Microbiology & Infectious Diseases! ID Transmission – and our sister brand, The Pathologist – are at booth B5-42 all weekend, so make sure to drop by and say hello if you manage to snag a spare minute during the show.

Each day, I’ll share a roundup of the sessions for those of you who couldn’t attend (or did attend but went to different talks than me!). Oh – and make sure you check out the special issue we put together just for the show!

I’m taking a slightly different approach to today’s roundup – dedicating it to one session in particular. A late-breaking session at last year’s ECCMID discussed how 10 children in the UK had required a liver transplant after a surge in severe hepatitis cases among young children. At the time of presenting, there were 84 total cases in England, with 43 fully recovered and 38 still in hospital. ECCMID 2023 revisited the issue to present an update on how the outbreak has evolved. Below, you’ll find an overview of Aikaterini Mougkou’s (Karolinska University Hospital, Solna, Sweden) session.

Severe acute hepatitis of unknown etiology in children

Epidemiological update, Aikaterini Mougkou

Since April 2022, over 1,000 cases of acute hepatitis of unknown etiology in children have been reported by 35 countries worldwide, including 46 requiring transplantations. Since then, the ECDC and the WHO have set up surveillance systems for the outbreak.

Reporting on European data, Mougkou highlights that:

• 585 cases have been reported in Europe by 22 countries, peaking in April 2022
• A similar trend was seen in UK cases
• About 75 percent of cases were aged five years or younger
• No difference in cases occurring in males or females.

Over 450 patients were tested for adenovirus, with 52 percent of cases returning positive. Positivity was highest in 0–5-year-olds compared with older age groups; 392 children were PCR tested for SARS-CoV-2, but only 10 percent were positive. Overall, among cases with at least one test result available for any pathogen, 52 percent were positive for at least one pathogen. Younger children were at highest risk of requiring a transplant.

Global data:

• Most cases were reported from the US and Europe, but Canada, Mexico, Indonesia, and Japan have also reported several cases
• 391 cases have been reported in the US with the same trends as Europe

What caused these hepatitis cases? The jury’s still out, and a large proportion remain without a cause. Mougkou reports that there are many hypotheses, but taking the lead is the adenovirus hypothesis, given that half of the children were positive with the virus in most countries and we know it is able to cause hepatitis (but usually in immunocompromised individuals, not previously healthy children).

The most likely hypothesis, however, is that the outbreak was caused by a combination of factors, but researchers are yet to establish causality. Perhaps at ECCMID 2024, we’ll be revisiting the issue once again with more evidence – and maybe a confirmed pathogenesis.

After reviewing the data and evidence, Mougkou highlighted the limitations faced over the past year, including over-reporting of suspected cases, variation in the timing of sample collection for testing, and extensive active testing after the initial outbreak alert which increased testing volume. However, the biggest issue, Mougkou noted, was the exceedance of hepatitis cases and viruses, such as adenovirus. There are currently no surveillance systems for adenovirus, meaning there are no historical levels of viral community circulation, and there are no baseline rates of hepatitis cases of unknown origin.

Mougkou also discussed the challenges of interpreting data because of the differences in surveillance practices, case reporting, resources and assays, among others. Before rounding off her presentation, she reinforced the importance of surveillance in public health for improving early outbreak detection – something we (should have) learned particularly well from COVID-19.