Afghanistan has restarted international flights. However, all routine immigrant and non-immigrant visa processing are suspended.
Point-of-entry screening has been introduced. Not everyone is being screened, but those who are and who show a temperature of more than 38ºC may be sent for isolation direct to one of 2 national hospitals (Kabul Infectious Disease and Afghan-Japan Communicable Disease Hospital in Kabul) or 5 provincial hospitals. These hospitals are outside of the Enhanced Security Zone.
Children under the age of 2 are exempt from presenting a COVID-19 test.
Travelers with proof of recovery from the virus within the last 90 days prior to boarding. Proof of a recent positive viral test and a letter from your healthcare provider or a public health official stating that you were cleared to travel.
More info at the CDC site
Travelers who did not get tested, are advised to stay home and self-quarantine for 10 days after travel.