The real number of swine flu cases in the United States could be “upwards of 100,000,” a top public health official estimated on Friday  far higher than the official count of 7,415 cases confirmed by laboratories.

The official, Dr. Daniel Jernigan, head of flu epidemiology for the Centers for Disease Control and Prevention, said at a news conference that the official number gave an inaccurate picture of the outbreak because so few mildly sick people were being tested.

He added that flu was more prevalent than usual, “something we would not normally expect at this time of year.” But he emphasized that most cases were mild. There have been 173 hospitalizations and 5 deaths reported to the agency.

The latest death, added Friday, was that of a 33-year-old man in Corpus Christi, Tex. The Associated Press reported that he died May 6 of viral pneumonia and had several health problems, including morbid obesity, an enlarged heart and an underactive thyroid.