The case numbers of children presenting with sudden and severe hepatitis infections are continuing to grow, a spokesperson from the World Health Organization (WHO) announced Tuesday.

“As of May 1, at least 228 probable cases were reported to WHO from 20 countries,” Tarik Jasarevic, a media officer at the Organization, told a Geneva press briefing.

There are “over 50 additional cases under investigation,” he added.

The death toll from the worldwide outbreak may have increased this week as well, as three children in Jakarta, Indonesia, are suspected to be the mysterious illness’s latest victims. These deaths, of children aged two, eight, and 11, bring the likely worldwide fatalities total to at least five.

The etiology of the unusual rise in childhood hepatitis cases is still unknown, though one leading hypothesis puts the cause of the disease as a type of virus, known as an adenovirus. In the UK, where the majority of cases have been found and the international alarm was first sounded last month, more than three-quarters of children with confirmed hepatitis tested positive for a particular adenovirus called F41.

However, if correct, this explanation raises further questions: “There are very few case reports in the global literature of adenovirus infection being associated with hepatitis in immunocompetent children,” explained Will Irving, Professor of Virology at the University of Nottingham, UK.

Indeed, the adenovirus is mostly known as a tummy bug or common cold virus, only leading to more complicated outcomes in immunocompromised patients. All the cases connected to the mysterious outbreak have occurred in previously healthy children, though, so if F41 is indeed what’s behind the recent uptick in hepatitis cases worldwide, “there will be a need to explain why the natural history of adenovirus infection has changed so dramatically in 2022,” Irving said.

Still, others remain skeptical. With so few cases worldwide, it’s not yet conclusive that the “outbreak” exists at all – it may be that we’re experiencing a rise in awareness of hepatitis cases, rather than in the number of cases themselves.

“There is still little data to define whether there is an outbreak, and for now the global risk is considered low,” noted Leandro Soares Sereno, Advisor for Viral Hepatitis Prevention and Control at the Pan American Health Organization (PAHO).

“As there is still no certainty about the origin of the disease, it is possible that we are becoming aware of a situation that existed before but went unnoticed because there were so few cases.”

While the WHO, as well as various national and international health agencies, are continuing to monitor the emergence of cases, scientists stress that parents and caregivers should not worry unduly about the outbreak. There are “only a small number of children affected,” said Deirdre Kelly, Professor of Pediatric Hepatology at the University of Birmingham and Consultant Pediatric Hepatologist at the Birmingham Women’s & Children’s Hospital, and most of those have recovered well.

“The most important [action for caregivers] is to pay attention to symptoms, such as diarrhea or vomiting, and to the color: if there are signs of jaundice – where the skin and whites of the eyes turn yellow – medical attention should be sought immediately,” advised Sereno.

“We recommend basic hygiene measures such as washing hands and covering your mouth when coughing or sneezing to prevent infections, which can also guard against the transmission of adenoviruses.”