A “large number” of extended family members and friends were at the party, the Pasadena Public Health Department said in a news release, adding the event took place after the city issued a stay-at-home order in March.
One patient at the party was coughing and not wearing a face covering, health officials said, and other party guests were also not covering their face or social distancing.
“As a result, Covid-19 spread among party attendees,” the department said.
Through contact tracing, investigators were able to identify more than five confirmed coronavirus cases from the party and “many more ill individuals,” according to the health department.
“This is an example of how good contact tracing can identify disease clusters and tell us more about the spread of disease in our community,” said Dr. Matthew Feaster, an epidemiologist with the department.
More than 66,550 people have been infected with the virus in California and at least 2,687 have died, according to Johns Hopkins University.
“Although we are moving forward with small modifications to the Safer at Home Order, gatherings of people who do not live in the same household are still prohibited,” Dr. Ying-Ying Goh, director and health officer of the department, said. “The virus remains highly contagious. Social distancing, frequent hand washing, and wearing face coverings remain our best defenses against the further spread of Covid-19 in our community.”