Liver lesions in patient with chronic active hepatitis C.
Enlarge / Liver lesions in patient with chronic active hepatitis C.

The number of unexplained cases has risen to 180 across 36 states, according to the Centers for Disease Control and Prevention.

The CDC deputy director for infectious diseases said in a press conference Friday that the death was reported to the agency Thursday. He didn't say which state the death occurred in.

15 of the 180 cases required a transplant. The cases all occurred in children under the age of 10, with the median age being around 2 years.

Over 600 cases have been reported across 31 countries, including 15 deaths, thanks to the latest US tally. Despite the growing numbers, international health experts are still scrambling to understand what is behind the illnesses after eliminating the most obvious possibilities, such as hepatitis viruses A, B, C, D, and E.

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Tricky numbers

The latest total of 180 cases may seem like a concerning rise from the 109 cases CDC reported two weeks ago, but most of the 71 newly reported cases were identified and actually occurred weeks to months ago. Only 7 percent of the cases happened in the last two weeks.

He was careful not to say that the cases were part of an outbreak, since the agency is not detecting an increase in the number of unexplained hepatitis cases. The 180 cases over the past seven months have not been clustered. They have been fairly evenly distributed among the 36 states, and the month-to-month case totals have not changed.

According to Umesh Parashar, chief of CDC's Viral Gastroenteritis Branch, there are between 1,500 and 2,000 cases of children being diagnosed with the disease each year. About 30 percent to 50 percent of the children's cases go unexplained each year. There were 180 unexplained cases over a seven-month period.

It is possible that the cases being highlighted have been there for a long time, and that they have not been identified or scrutinized previously.