A hot zone is a place that is really, REALLY dangerous because of germs or other things that can make people really sick! Just like when you are sick and your mommy or daddy wants to keep you away from other kids so you don't spread your germs, but on a much bigger scale!
Sometimes, there are diseases or viruses that can spread really easily and quickly and make a lot of people sick. When this happens, scientists and doctors need to be very careful and wear special clothes and masks so they don't get sick too. They set up a special area called a hot zone where only the people who are wearing these special clothes and masks are allowed to go, so that they can try to stop the disease from spreading to even more people.
You might have heard of a hot zone in the news because there was a really dangerous virus going around called Ebola. Scientists and doctors had to wear special suits and masks to protect themselves from the virus, and they worked really hard to try to help the people who were sick. It's very important to try to stop diseases from spreading, and hot zones are one way that we can do that to keep people safe and healthy!