The state Department of Health issued a high level of bacteria advisory this 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 were also issued for Waimanalo Beach and the central part of Sandy Beach Park.

Levels of enterococci were at 393 per 100 milliliters at Hanauma, 213 per 100 milliliters at Waimanalo, and 583 per 100 milliliters at Sandy Beach.

Those levels exceeded the threshold 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 effected beaches and the advisories will remain in effect until water sample results no longer exceed the threshold. Updates, including the cancellation of the advisories, are available at the state’s Clean Water Branch website.