单项选择题

Swine Flu in New York
The Centers for Disease Control and Prevention has confirmed cases of swine (51) in eight students at a New York preparatory (预科的) school, Mayor Michael Bloomberg said Sunday. The students have had only (52) symptoms and none have been hospitalized, he said. Some of the students have already recovered.
More than 100 students were absent from (53) due to flu-like symptoms last week. New York health officials tested samples for eight students Saturday and determined the students were probably. (54) from swine flu, and the CDC confirmed the (55) on Sunday, Bloomberg said.
The announcement brings the (56) of confirmed swine flu cases in the United States to 20. Bloomberg said there is no (57) of a citywide outbreak of the flu, and no sign of a potential outbreak of swine flu at (58) schools.
Some students at the school (59) spring break in Mexico, Bloomberg said, but authorities have not determined (60) any of the students with a confirmed case of swine flu was in Mexico. Someone who traveled to Mexico may not have had any flu symptoms but (61) on the flu to someone else, he noted.
Bloomberg called on students who are home sick to (62) home for 48 hours after their symptoms subside.
If symptoms are normal for a regular kind of flu, there is (63) need to go to a hospital, said Bloomberg. If symptoms become severe, as (64) any illness, people should go to the hospital, he said.
St. Francis, which has 2,700 students, announced it will remain closed for two days. (65) whether the students’ illnesses have been minor because they’re young and healthy or because it is a minor strain of the virus, Frieden responded, "We don’t know. \