strep throat can have an incubation period that lasts between two to five days this means a person who is exposed to the bacterium that cause this illness may develop the illness two three four or five days after his exposurein most cases however the incubation period for strep throat lasts for about three dayspeople who have been infected with the bacteria that cause strep throat are contagious until they have received antibiotic treatment for 24 hourshis period can last for as little as two days or as long as five days most of the time however a person will develop symptoms of the illness three days after he has been infected ad most people who are in the incubation period for strep throat are not even aware they have been exposed