Kaiser Permanente is still trying to determine the source of bacteria responsible for 19 recent cases of Legionella infection identified at a hospital in the San Francisco Bay Area.

The 19 infections were linked to Kaiser’s medical center in Santa Clara. Most of those who fell sick are recovering at home, Kaiser said in a recent statement.

The bacteria were identified through “robust routine internal monitoring processes,” according to Kaiser.

“Our medical center is a safe place to visit and receive care,” the health system said.

Kaiser did not specify how ill those infected are, nor did they say specifically how the bacteria were detected.

Infection can occur when Legionella — which appears naturally in environments such as lakes and streams — gets into building water systems and people breathe in mist containing the bacteria, according to the U.S. Centers for Disease Control and Prevention. The bacteria grow best in warm temperatures, between 77 and 113 degrees.

The disease does not spread from person to person.

The most severe form of Legionella bacteria infection leads to Legionnaires’ disease, a serious and potentially deadly type of pneumonia, the CDC says. Legionnaires is treatable with antibiotics, but early treatment improves the odds of recovery.

A milder form of Legionella infection called Pontiac fever can also cause aches and headaches.

Legionella can grow and spread in devices such as hot tubs, cooling towers, hot water tanks, complex plumbing systems, showerheads, sink faucets and decorative fountains, according to the California Department of Public Health. Most people who are exposed to Legionella don’t get sick, but the bacteria can cause serious infections in some cases.

“While we work to determine the source, out of an abundance of caution, last week we concluded additional water treatment measures and preventive measures to ensure the safety of all patients, employees, and visitors,” Kaiser said in its statement. “As a result of mitigation efforts, our hospital and medical office building continue to operate normally. “

About 1 in 10 people who get Legionnaires’ disease die due to complications from their illness, the CDC said. For those who contract it during a stay at a healthcare facility, about 1 of every 4 are expected to die.

Legionnaires’ disease was discovered in 1976 after a major outbreak affecting attendees of a convention of the American Legion in Philadelphia, according to the CDC. The outbreak led to 221 illnesses across Pennsylvania, and 34 deaths.

Investigators eventually suspected that the bacteria were airborne and had infected people after contaminating the air conditioning system at the convention hotel.

“Since 1976, air conditioning systems changed and agencies around the world have more stringent cleaning and hygiene standards for cooling towers and large-scale air-conditioning systems,” the CDC says.

Other ways facility managers can reduce the risk of Legionella include disinfecting cooling towers and water systems, establishing a water management program and routinely performing water system maintenance.

Legionnaires’ disease has been on the rise since the early 2000s, according to the CDC.

In 2024, seven cases of Legionnaires’ were reported in the northwestern corner of the city of Westminster, according to the Orange County Health Care Agency. No source was ever found for that outbreak, “as is so often the case,” the agency said last week.

When two people died after visiting a day spa in Richmond in 2023, Contra Costa County health officials found high levels of Legionella bacteria in the spa, and located two other guests who had lab-confirmed Legionnaires’ disease. Contra Costa County health officials said the hot tub at the day spa didn’t have a permit, and had never been inspected by health officials.

And in 2022, health investigators uncovered the likely source of 17 Legionella infections in Napa County — all of whom either lived, worked or had visited downtown Napa. Sixteen people had to be hospitalized, with 10 needing intensive care, and one person died, according to the CDC’s Morbidity and Mortality Weekly Report.

Investigators found high levels of Legionella bacteria in a cooling tower at what was then the Embassy Suites Napa Valley on California Boulevard, Napa County health officials said. None of the cases were guests of the hotel.

According to the MMWR, investigators said the cooling tower had malfunctioned, leading to either very little or no injection of chemicals that would prevent bacterial growth.

The report noted that cooling towers can spread Legionella bacteria over a wide area, with people living within 0.6 miles from a tower at highest risk of infection.

“Cooling towers without a comprehensive water management program or lacking routine maintenance are associated with an increased risk for Legionella colonization,” the report said.

Cooling towers were also the culprit in a large Legionnaires’ disease outbreak in New York City last year, which was linked to 114 cases, 90 hospitalizations and seven deaths. Legionella bacteria that genetically matched specimens in patients was found in cooling towers at Harlem Hospital and a nearby construction site, according to the city.

The CDC in 2024 also reported on outbreaks of Legionnaires’ disease aboard two cruise ships. Investigators found a previously unidentified source of the bacteria: “hot tubs located on private balconies, which have become more common as new ships enter service” and “are subject to less stringent operating requirements” than public hot tubs.

“Hot tubs can be a source of Legionella growth and transmission when they are inadequately maintained and operated,” the CDC said.

Times librarian Cary Schneider contributed to this report.

For the last several months, wildlife experts have been alarmed by a large influx of dead and emaciated seabirds washing up on California beaches.

While experts had been recording high mortality rates for brown pelicans for several years now — the result of harmful algal blooms, or “red tides” — this die off appears different.

Now it’s not just pelicans that are being impacted, it includes other water birds, such as Brandt cormorants, loons, common murres, and grebes.

The suspected culprit in this case is subtler and more insidious than the algal neurotoxin known as domoic acid. Experts say these recent deaths are likely tied to an extreme marine heat wave that is causing deadly changes in food availability.

Up and down the California coast this spring, ocean temperatures have skyrocketed. In some places, temperatures have climbed 4 to 8 degrees higher than average, breaking all kinds of historical records. For instance, in La Jolla, nearly 30% of the readings taken off the Scripps Pier this year have exceeded previous temperature records.

“If the ocean is warmer than normal, it can impact the food web in multiple ways,” said Tamara Russell, a marine ornithologist at UC San Diego’s Scripps Institution of Oceanography.

She said fish and other organisms that require cooler waters to survive may swim north or dive deeper in the water column — making them less available for the birds that feed on them. In addition, warmer conditions can stifle the amount of nutrients rising to the water’s surface, resulting in “cascading impacts on the entire food web.”

She said the number of birds coming into rescue centers has increased in tandem with warmer than average ocean temperatures. The marine heat wave, according to researchers, spans from roughly San Francisco to the Mexican border.

Not all experts agree the spike in bird deaths is due solely to increased water temperature.

Krysta Rogers, the lead for bird investigations at the California Fish and Wildlife Department, said she began receiving reports of dead and weakened birds beginning as far back as last summer.

Most of the affected birds were youngsters that had been born that year, following a robust breeding season, she said. The department identified starvation as the primary cause of death. Some birds also suffered from gastrointestinal parasites or fungal respiratory infection, issues wrought by a weakened immune system.

Living at sea isn’t easy. “They have to keep warm, they have to swim after their prey,” Rogers said. “It’s very energetically demanding. And so if they miss a meal or two, that can kind of tip them over the edge. Then it just kind of spirals from there.”

From January through April, the department received 295 reports of dead birds submitted through its website: 193 for Brandt’s cormorants, 68 for common murres and the remaining 34 for a combination of brown pelicans, grebes and loons.

Of 50 cormorants submitted to the lab for necropsies from May of 2025 to April 2026, 46 were juvenile, one was an adult and the rest were in a condition too poor to determine. Of the 35 murres submitted between July 2025 and April 2026, 24 were juveniles, 9 were adults and two were undetermined.

According to Rogers, it’s not uncommon for a population boom to lead to an uptick in deaths — translating to more juveniles that simply don’t survive as they dodge predators, contend with storms and compete with other hungry birds for food. Winter is a particularly challenging time for the inexperienced hunters.

The marine heatwave that has gripped the waters off California may play a role in the bird’s survival, but it’s likely not the only factor, she said.

Rebecca Duerr, a veterinarian at the rescue clinic, said she and other wildlife officials started seeing a “tremendous” influx of dead birds washing up on California beaches in March and April.

She said reports from the Channel Islands suggested breeding colonies of pelicans and cormorants were collapsing. “Like thousands of dead babies,” she said.

She said while a third of the pelicans she’s seen could rightly be considered starving, many of the others have come in with injuries — which, she said, also suggest a food availability problem.

“It’s my subjective impression, but when the pickings get slim out on the ocean, the pelicans take more risks… and more likely to be hanging around public fishing piers or begging at Redondo Beach,” Duerr said “That’s like last resort feeding opportunity.”

She’s seen scores of birds maimed and injured by fishing gear, along with injuries she classifies as “malicious,” such as stab wounds.

Duerr and Jaret Davey, a volunteer coordinator at Wetlands & Wildlife Care Center in Huntington Beach, said several birds have also come in with raging fungal infections in their lungs — the type of infection an animal only gets when its immune system has been suppressed by disease or malnutrition.

“When sea birds become emaciated, they pretty much don’t have any energy to put towards immune function, and their air spaces are a nice, warm, moist location. They become super susceptible to aspergillosis,” she said, naming the fungus the care centers are finding.

So far, sea mammals don’t seem to be impacted.

“We’re seeing conditions in our monitored populations that are typical for this time of year,” said Krista Maloney, with the Sausalito-based Marine Mammals Center.

The Los Angeles County Department of Public Health is investigating a confirmed measles case in a resident who recently traveled internationally, the agency said in a release Saturday.

This is the fifth measles case identified by the county this year as outbreaks increase across the U.S. and globally.

The infected resident arrived at the Los Angeles International Airport on Thursday on Alaska Airlines Flight 1354. Other travelers at Tom Bradley International Terminal B that day between 6 a.m. and 8 a.m. may have been exposed to the virus, officials said.

Public health officials are advising residents to check their immunization status and watch for symptoms if exposed. The measles-mumps-rubella vaccine is the most effective protection from measles, according to the public health department.

“As measles cases increase, it is important that residents take steps to make sure they are fully protected,” L.A. County Health Officer Muntu Davis said in a statement. “The MMR vaccine is the safest and most reliable way to prevent measles and protect yourself, your family, and your community.”

In coordination with the federal Centers for Disease Control and Prevention, L.A. County Public Health will notify travelers seated near the infected person on the flight.

Affected travelers are at risk of developing measles from seven to 21 days after exposure to the virus. Symptoms include rash, fever, cough and red, watery eyes.

Measles can lead to complications including pneumonia, brain swelling and even death. Those with symptoms should notify their healthcare facility before visiting, officials said.

So far this year, 1,814 measles cases have been confirmed nationwide, including 48 in California.

In January, health officials recorded the most amount of cases since the U.S. achieved elimination of the virus in 2000.