Since October, over 1,000 children worldwide, more than 350 of them in the United States, have been diagnosed with hepatitis, or swelling of the liver, with no known cause.
Every year, hundreds of children are diagnosed and treated with hepatitis, and the number is expected to climb as mysterious cases continue to rise worldwide.
According to the World Health Organisation (WHO), 21 countries have now detected severe hepatitis of unknown origin among children mostly under the age of 10 since early April. At least 26 youngsters have required liver transplants.