Chikungunya
About 1 in 1000 people who get chikungunya die from the disease.  People older than 65, newborn babies, and people with other medical problems are most likely to have the most dangerous problems.  Chikungunya is especially dangerous for newborns because they can get the virus from their mothers during childbirth, and because newborns' immune systems have to grow before they work as well as adults'.  This makes it much more difficult for newborns to fight off the virus.