It’s very hard to know precisely how many Christians there are in Afghanistan, because they must keep their faith completely secret.
Afghanistan is number one on the Open Doors World Watch List. Persecution has increased since the Taliban took control last August. Christian converts face violent consequences if their new faith is discovered. They have to flee the country or they will be killed.
This is very little different from the situation faced by those Christians to whom the book of Revelation was written. (See other post)