JULIAN, Calif. -- A total of 89 out of nearly 200 children who recently attended a five-day camp for asthmatic youths in Julian were sickened by swine flu, 10News' Carole Sullivan reported on 10News This Morning Thursday.

Organizers of the American Lung Association camp, which was held from June 21-26 at Camp Marston, sent parents letters in recent days notifying them about the outbreak, The San Diego Union-Tribune reported.

At least three parents said camp doctors should have notified them sooner and done a better job of isolating sick children, according to the newspaper.

Dr. Michael Welch, a San Diego pediatrician and allergist who oversaw the volunteer health staff during the camp, said doctors didn't realize something unusual was happening until four days into the camp, and by then they thought most of the symptoms didn't point to anything serious.

"It's always unfortunate when this happens," he told the Union- Tribune. "I'm not sure we could have done things differently."

Four of the 89 campers who fell ill were hospitalized. Most cases of swine flu, caused by the H1N1 virus, have been mild, according to county public health officials.

As of Wednesday afternoon, there were 532 confirmed cases of swine flu in San Diego County since the virus was first reported earlier this year.

Five cases turned out to be fatal.

A fifth person in San Diego County has died in connection with the H1N1 "swine flu" virus, the county Health and Human Services Agency reported Thursday.

The 36-year-old man, who had underlying health issues, died Saturday, according to the HHSA.