(Updates with death in Los Angeles)

WASHINGTON, June 1 (Reuters) - Cases of the new H1N1 flu virus have been found in all 50 U.S. states and tests have confirmed the virus in more than 10,000 people across the nation, U.S. officials said on Monday.

The U.S. Centers for Disease Control and Prevention has said the confirmed tests represent about one in 20 of the actual number of infections, which would bring the total number of U.S. cases to around 200,000.

In Los Angeles, health officials reported the county's first death from the disease, a middle-aged woman who had underlying health problems.

The woman, whose name was not released, died in May and was one of 102 cases of the swine flu virus in Los Angeles County.

"Every death is regrettable, but given the number of H1N1 cases in Los Angeles, identifying the new H1N1 strain in someone who passed away with severe respiratory disease is not unexpected," Los Angeles County Health Officer Jonathan Fielding said.

Seventeen deaths in the United States have been definitively linked to the swine flu virus, the CDC said. It was not immediately clear if that total included the Los Angeles County case.

The virus, which spreads easily and causes mostly mild disease, has been diagnosed in 17,564 people in 64 countries, killing 115, according to the World Health Organization.

It was newly found this week in patients in Bulgaria, Vietnam and Jamaica.

Although H1N1 swine flu appears mild, it affects mostly older children and young adults, and experts worry it could change into a more dangerous form. (Reporting by Maggie Fox and Dan Whitcomb)