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As RSV infections spike in San Francisco, here’s what to know ahead of ‘tripledemic’ season

A green pop-up tent with the words COVID, FLU, RSV and TEST on its edge shelters people on a sunny day.
RSV levels in San Francisco wastewater have spiked in recent weeks. | Source: RJ Mickelson/The Standard

RSV—or respiratory syncytial virus—is spiking in San Francisco, according to WastewaterSCAN data, a program that traces pathogens in municipal sewer treatment plants.

RSV is a virus that often causes colds and can be severe for infants and older adults, according to the San Francisco Department of Public Health.

The department monitors wastewater data to help keep track of trends and local case numbers.

New data from WastewaterSCAN shows RSV rising from an August low where no virus—a score of 0—was detected in city sewage to an Oct. 28 high, with a score of over 46 parts per million at the Oceanside plant and around 26 at the Southeast plant. The start of November shows a slight drop in virus detection, but it remains higher than the last rise in September.

A chart shows RSV infection rates in San Francisco spiked between August 2023 and November 2023.
A graph shows the viral levels of RSV between August and November in San Francisco's two water treatment plants. | Source: WastewaterSCAN

However, the rise in RSV is still lower than over a similar period last year, when viral loads scored 55ppm by November 2022—rising from 2ppm in August.

A chart shows RSV infection rates in San Francisco spiked between August 2022 and November 2022.
A graph shows the viral levels of RSV between August 2022 and November 2022 in San Francisco's two water treatment plants. | Source: WastewaterScan

People with an RSV infection typically display symptoms including a fever, coughing, a runny nose, wheezing and difficulty breathing. 

Simple measures offer some of the best ways to slow the spread of RSV. Those can include staying home when sick, wearing a high-quality mask if you are sick or in crowded or indoor areas, covering your coughs and sneezes with a tissue or your shirt sleeve and not your hands, and washing your hands often with soap and water for at least 20 seconds, according to the health department.

What To Know About Tripledemic Season

A group of people are seen, some are wearing masks and rain coats on a city street. Some of the people are not wearing masks.
Some people continue to wear face masks while others opt out in Union Square in San Francisco on July 18, 2022. | Source: Juliana Yamada/The Standard

Influenza, RSV and Covid are circulating this fall, but not yet at the rate that worried public health agencies a year ago and earned the phenomenon the moniker "the tripledemic."

As we approach the time of winter when these diseases usually peak, around December to February, experts warn that the patterns can change at any time and advise people to take precautionary measures, such as getting vaccines.

For those concerned about respiratory viruses, there is good news: The Food and Drug Administration approved two RSV vaccines and another shot for use in vulnerable populations.

Several vaccine makers also have updated their Covid boosters, which are recommended for those over age 5.

Public health experts generally expect a milder flu season this year. Last year was especially severe as social activities returned to normal and Covid social-distancing rules ended. Experts say that more than two years of staying at home and taking precautionary measures protected people from influenza viruses but also reduced their immunity once they resumed normal social activity.

“We are seeing pretty decent matches with the flu vaccine, which is going to help, and we haven’t seen a big take off locally and nationally yet of the flu,”  said Dr. Marlene Millen, an internal medicine doctor at the University of California San Diego.

If you still haven’t gotten the latest vaccines for flu and Covid, it is not too late. Here’s what you should know about this cold and flu season.

When asked about the outlook for respiratory diseases, Dr. Peter Chin-Hong, an infectious disease physician at UC San Francisco, said, "The big answer is that it is uncertain."

A blue tent with voting signs and people wearing masks outside a grandiose building.
Voters wearing face masks cast ballots for the 2020 presidential election at a polling station outside San Francisco City Hall on Oct. 5, 2020. | Source: Liu Guanguan/China News Service via Getty Images

Experts say the exact infection patterns of any of these respiratory viruses cannot be predicted due to several factors, such as human interaction, travel and preventative habits. According to the California Department of Public Health, it is too soon to know how severe each of the diseases will be this season.

“As more people are heading indoors for school, fitness routines and festive gatherings, Californians are getting exposed to respiratory viruses,” said Dr. Tomás Aragón, the director of the state public health department in a press release. “Anyone can be affected by winter illnesses. However, some individuals, including older adults, people with weakened immune systems or chronic conditions, pregnant people and young children, are at higher risk for severe illness and death.”

Chin-Hong said that while infections from Covid have plateaued in the past few months, there may be an uptick in infections on the horizon, especially among vulnerable populations.

The state’s respiratory infections reports show that RSV infections are currently rising ahead of flu and Covid. But the state also has more tools to battle the disease compared with last year. The new RSV shots, combined with the leftover immunity from last year, Chin-Hong said, may result in a comparatively milder RSV season than last year.

What experts are worried about is the rate of infections for all three of these respiratory diseases peaking together at the same time, which can overwhelm health care systems. That scenario is now known as a “tripledemic.”

“Every year, that’s a possibility. I always cross my fingers that that doesn’t happen because we get very busy in the hospitals, especially in the clinics and other places,” Millen said. “Every year since Covid, it has been a concern that all three will kind of peak at once. And if that happens, then our health care system gets even more strained.”

Millen said even though infections could spread faster than predicted, there is no reason to panic.

“These aren’t new viruses, so all of the risks are already there,” she said. “The biggest thing is listening to what is going on and paying attention.”

Several treatments can help reduce serious infections and death rates. Experts also say that people should continue to exercise preventative measures such as wearing masks, washing hands and staying away from crowded places, as they did during the height of the Covid pandemic. 

All three viruses have similar symptoms in that they attack the respiratory system and cause symptoms like cold, fever, cough, stuffy or runny nose, body aches and fatigue, as well as chills. Infections from all three viruses can also be asymptomatic.

Doctors recommend isolating if you develop any respiratory systems or fever at all, to avoid putting others around you at risk, especially young children and the elderly.

“If you’re sick, stay home,” Millen said. “Viral loads are really high in those first few days of illness, and that’s when spreading illnesses happens, so just wait.”

For influenza and Covid, the state Department of Public Health recommends vaccinations for all who are 6 months or older. Anyone over 6 months old should get the annual flu shot, while those 5 years and older should also get the updated Covid booster this year.

For RSV, doctors recommend all those who are eligible to get vaccinated. This includes adults who are 60 or older, pregnant women, infants who are 8 months or younger and high-risk children between 8-19 months old.

For those who do not have health insurance, California has several resources to get free vaccines, including federally qualified health centersBridge Access Program for Covid vaccines and the Vaccines for Children program.

Earlier this year, three shots were approved for RSV: two vaccines and an antibody shot.

The two vaccines are approved for use in elderly and pregnant women. The vaccine for pregnant women is recommended to be used between weeks 32 and 36 of the pregnancy and will reduce the risk of infection in newborns. The vaccine for seniors is available for all adults 60 or older, as they are at higher risk from infections than younger adults.

The antibody preparation provides lab-prepared monoclonal antibodies to infants and young children at high risk from infections who may not be able to produce their own antibodies.

There is currently a shortage of the antibody shot, which is causing concern among pediatricians, especially as RSV infections rise this winter. 

CalMatters contributed to this reporting.
George Kelly can be reached at