ABC News Cases of norovirus are rising across the United States, doubling over the last few months, according to updated data from the Centers for Disease Control and Prevention (CDC).
Nearly 14% of tests came back positive for norovirus during the most recent week ending Nov. 15, compared to roughly 7% about three months ago.
Test positivity is a metric used to identify how many people are confirmed to have norovirus after an illness is suspected. Health experts have said that, like other measurements, test positivity is imperfect as it depends on the number of tests that are ordered, which can vary.
Last December saw a record-breaking rate of norovirus cases in the U.S. with nearly 25% of tests coming back positive. Cases had been trending down since then but have begun to rise in recent weeks, CDC data shows.