The state Health Department issued an advisory of high levels of bacteria Wednesday afternoon for Hanauma Bay, resulting in the closure of the popular snorkeling spot.

The high levels were discovered during routine beach monitoring. High-bacteria advisories also were issued for Waimanalo Beach and the central part of Sandy Beach Park.

At Hanauma, levels of enterococci were at 393 per 100 milliliters.

At Waimanalo, levels of enterococci were at 213 per 100 milliliters.

At Sandy Beach, levels of enterococci were at 583 per 100 milliliters.

The levels of enterococci exceed the threshold level of 130 enterococci per 100 milliliters, indicating that potentially harmful microorganisms such as bacteria, viruses, protozoa, or parasites may be present in the water. Swimming at beaches with pollution in the water may make people ill, particularly children, the elderly and people with weakened immune systems.

“Fortunately, while swimming-related illnesses can be unpleasant, they are usually not very serious,” the Department of Health said. “They require little or no treatment or get better quickly upon treatment, and they have no long-term health effects.”

Gastroenteritis is the most common illness associated with swimming in water polluted by fecal pathogens. Other minor illnesses associated with swimming include ear, eye, nose and throat infections.

Signs have been posted at all affected beaches and the advisories will remain in effect until water sample results no longer exceed the threshold level of 130 enterococci per 100 milliliters. Updates, including the cancellation of the advisories, are available at at the state’s Clean Water Branch website, 808ne.ws/waterupdates.