The Centers for Disease Control and Prevention (CDC) reported this week that they're seeing a strange spike in cases of a mysterious condition that can cause paralysis — especially among children. The virus, called acute flaccid myelitis (AFM for short), often starts with a viral infection, like the ones that can cause bronchitis, and leads to scary symptoms such as weak limbs, difficulty breathing and swallowing, and, in severe cases, paralysis. If you feel like you've heard about this before, you're probably right — the first major spike in cases came in 2014, following a larger-than-usual outbreak of a respiratory illness called enterovirus D68 (or EV-D68 for short) that usually only causes cold-like symptoms such as runny nose, coughing, sneezing, and body aches. That year the CDC counted 120 cases of AFM spread across 34 states. Since then, the number of cases has decreased but not disappeared: In 2015, the CDC found 21 confirmed cases of AFM in 16 states. And now, in a report released this week, the CDC showed that cases have been again increasing in the U.S., with 50 confirmed across 24 states so far in 2016. Specifically, there were around five cases in May, 10 in June, 15 in July, and 20 in August. But the report also notes that it's a little difficult to interpret any trend here because doctors aren't required to report individual cases of AFM. So we don't know how (in)complete these data are. This time around, there doesn't seem to be a clear link to EV-D68. Other viruses, such as West Nile or adenoviruses, which can cause common conditions, including pneumonia and bronchitis, have also been linked to AFM. (There's currently no evidence to suggest a connection to the Zika virus.) All of this sounds really scary, but it's important to remember that AFM remains incredibly rare. And the best way we know of to prevent it is to protect yourself from those original viruses. This means washing your hands frequently, staying away from sick people, and warding off West Nile-carrying mosquitoes (which should become less of a concern as we march toward cold and flu season).