A student from Mexico was confirmed late Monday night as the seventh case of swine flu in Israel, Army Radio reported. At least 61 people have been killed by the epidemic around the world, and the World Health Organization has confirmed 4,800 cases, including the first in mainland China. Last Thursday, a woman who returned to Israel from Mexico with her husband was hospitalized along with her husband, who was confirmed to have contracted the disease. She and her husband were released and asked to remain in their house. The Ichilov Medical Center in Tel Aviv, where they were hospitalized, notified her on Thursday that she had also contracted the disease. On Wednesday, a 59-year-old woman who was hospitalized in Nahariya was confirmed to have the virus. She contracted it on a flight from Spain, becoming the first Israeli to be infected without having visited Mexico. Hospital officials said she was in good condition. A study published Monday in the journal Science estimated that Mexico alone may have had 23,000 cases by April 23, the day it announced the epidemic. The study estimates swine flu kills between 0.4 percent and 1.4 percent of its victims, but lead author Neil Ferguson of Imperial College, London, said the data remained incomplete. "It's very difficult to quantify the human health impact at this stage," he said.