NEW YORK (AP) _ Michael Jackson is suffering from a viral infection and had been ill for a week or more before he collapsed during a rehearsal this week, a doctor said Friday.

Dr. William Alleyne said diarrhea from the infection led to severe dehydration, which in turn brought on an irregular heartbeat.

Jackson remained in the intensive care unit at Beth Israel Medical Center North. His personal physician, Dr. Allan Metzger, said he could be hospitalized for at least another week.

Metzger said the singer's condition was ``serious but I wouldn't characterize it as life-threatening.'' He was listed as serious be stable.

The doctors said there was no evidence of drug use.

Jackson, 37, collapsed at the Beacon theater Wednesday night while rehearsing for an HBO special that has since been postponed. Alleyne said Jackson had been ill for seven to 12 days before his collapse.

Jackson was disappointed about not being able to perform, he said.

``He tried to convince the medical team that he could give it a go,'' he said. ``We put our foot down.''

The doctors said Jackson had pictures of his family and his favorite Disney characters brought into his private room. Some of his hardiest fans braved the cold Friday outside the hospital to with him well.

Several dozen of them looked up at the hospital windows, shouted and waved. Some from a nearby high school chanted ``Michael! Michael! Michael''

``Maybe he can hear us and he feels good about it; that will help him,'' said Rita Costa, 22, of Hillside, N.J.

Jackson was visited Friday by his wife, Lisa Marie Presley, and Diana Ross, his longtime friend and mentor. Neither spoke to the horde of reporters outside the hospital.

The singer's fans took up a collection in the near-freezing weather to buy a giant card that they could all sign and send inside.

Jackson also received a get-well wish from his estranged sister, La Toya, who had earlier told the Daily News that she believed her brother was faking his illness to get publicity.

``My thoughts and prayers are with him,'' said a statement issued by her New York spokesman, Len Fink.

Ms. Jackson, who had singing engagements in Germany, could not be reached at her hotel on Friday. But Fink said she made the disparaging comments before she learned all the details of his illness.

Her husband, however, had something else to say.

``Len Fink was unauthorized to give that statement,'' Jack Gordon said from Germany.

Jackson's publicist, Lee Solters, refused comment on the wayward Jackson sister's opinions.

``We don't comment on anything that La Toya has to say,'' he said.

Jackson's fans, meanwhile, were content just to be there.

``He was the best ... He is the best,'' said Sasha Penalo, 14, part of the group that held up signs reading, ``Michael, you are not alone.''

It was the second Jackson vigil for the Brazilian-born Costa. She was in London when Jackson collapsed and was hospitalized there.

``We are here from Brazil, from Italy, from London, from all over the world,'' she said. ``All the fans want to get together to say we love you.''