Worries have widened in recent days over the number of people in Liberia who may have been exposed to the country’s first Ebola case in more than two weeks, a street vendor who lived in a one-bathroom house shared with 52 others in a Monrovia suburb and who had sold food at a school where more than 1,900 students are enrolled.

The patient, identified as Ruth Tugbah, 44, had been in contact with a range of people, including her children and a pastor who had sought to comfort her, after she developed a fever and was contagious, aid workers said Tuesday.

Ms. Tugbah received a diagnosis of Ebola on Friday, ending a short-lived period of optimism that Liberia would be the first of three afflicted West African countries to emerge from the worst epidemic of the deadly virus in history.

More than 10,000 people have died in the past year from Ebola, nearly all of them in Liberia, Guinea and Sierra Leone. Liberia has made the most progress toward recovery.