Our progress against opioid harms is being challenged by emerging synthetic agents, Covid-19 is still surging, and we have a new tool to fight flu. And I could use your help prioritizing among climate health concerns. Let’s jump in.

An emerging opioid threat in California

In April, a 16-year-old died in his bedroom in San Francisco from a drug his mother had never heard of.

The medical examiner found cychlorphine, a newly circulating synthetic opioid roughly ten times more potent than fentanyl.

His mother gave him two doses of naloxone (Narcan) before paramedics arrived, and it still wasn’t enough.

Cychlorphine is so unfamiliar it took two weeks for the coroner to identify it in the boy’s system, through special lab testing. The drug isn’t yet named as an illegal or controlled substance in California law, so San Francisco’s DA is now pushing state legislators to add it to the controlled substances list.

Last week, San Francisco police arrested four suspected dealers, seizing over 20,000 counterfeit pills. This story has been getting a lot of attention, including a recent New York Times feature. I wanted to provide some context for what’s being called our “new drug war.”

Why this is a public health problem.

The opioid epidemic has unfolded in overlapping waves shaped by the drugs causing deaths. Prescription pain pills drove the first wave in the 1990s and 2000s.

As prescribing practices tightened, heroin use increased. Then, around 2018, came fentanyl. It was cheap to produce, easy to access, and so potent that deaths surged.

Cychlorphine is another ultra-potent synthetic opioid. Although its role in California’s drug supply is still uncertain, the last thing we need is another wave, driven by an even higher potency opioid.

Three Waves of the Opioid Epidemic

The scale of the opioid problem.

California recorded 4,977 opioid deaths in 2025. That’s about one every two hours, around the clock.

In 2024, fentanyl was involved in 88% of the state’s 5,426 opioid deaths.

Overdose in the leading cause of death for Californians aged 14-44— more than cancer, accidents, heart disease, or infections. The crisis touches all of us, directly or indirectly. But there’s hope…

Progress. There’s good news underneath all this.

California’s overdose rate has been falling since its 2023–2024 peak.

We’ve seen a 41% drop in mortality over two years.

This progress is driven by investment in solutions. Wider Narcan access, growing awareness, treatment expansion, and crack-downs on illegal operations.

Opioid settlement: Many of the programs driving our success are funded by the “global opioid settlement”—similar to the master settlement against Big Tobacco in the late ’90s.

A $59 billion settlement has been reached between U.S., state, local, and tribal governments and the pharmaceutical companies that manufactured, distributed, and sold opioids.

California joined the national suit that held these companies responsible for marketing opioids misleadingly, downplaying risks, and distributing them recklessly.

The state’s share is about $2 billion, paid out to nearly every county, city, and town to address and prevent further harm. You can see how much your city or town received in the global settlement here.

Separately, the state also invested more than $1 billion statewide for mitigation strategies, plus $88 million to crack down on illegal opioid sales. It may feel like too little, too late, but resources are flowing to address the opioid crisis in California.

The problem of invisibility.

The emerging synthetic agents that could threaten our progress can outrun our ability to detect them. There’s no routine assay, no test strip, and no wastewater signal for cychlorphine yet. San Francisco is working with wastewater laboratories, like Biobot, to develop tests to detect new drug threats as soon as they emerge.

A personal stake in solutions.

Last month a team I work with published our study on wastewater surveillance for overdose prevention. We found that increased fentanyl levels in wastewater correlated (but not strongly) with increased 911 calls for opioid overdoses in Marin County.

Wastewater can’t predict overdose risk quite as well as it can predict exposure to viruses—but early identification and tracking of novel, high potency substances like cychlorphine is a clear use case for wastewater monitoring.

Take home. I don’t see cychlorphine becoming the new fentanyl. Since its emergence, we haven’t seen a major jump in overall overdoses, and we’re better equipped to reverse overdoses and get people into treatment.

But the situation exposes a vulnerability: we’re seeing how ultra-potent synthetic opioids can appear and spread faster than our detection systems can respond. The challenge is to build the systems to catch the next one earlier.

What you can do.

Cychlorphine, like fentanyl, can appear in pill or powder form and has been found in pills that mimic prescription pain medications.

Only take medications dispensed by a pharmacy. Never take anything from a friend, a dealer, or an online seller, no matter how legitimate it looks.

Counterfeit pills look like the real thing, and current fentanyl test strips won’t catch cychlorphine.

If you or someone with you uses drugs, keep naloxone on hand.

This  (CYCHLORPHINE) drug is so potent, it could take multiple doses to reverse an overdose. Call 911 immediately either way. And don’t use drugs alone: someone needs to be present to recognize an overdose and act.

If you or someone you know is struggling with substance use, you’re not alone: call or text 988 to reach someone who can help.

Poll

Next week, I’m headed to Climate Week in New York to connect with partners working on climate and health. I’d love to know what’s top of mind for you as I join these critical conversations. Please use the comments section to offer other suggestions. I’ll report back next week!

POLL When you think of the health impacts of climate change in California, what concerns you most? Wildfire smoke Extreme heat events Flooding Drought Emerging infectious diseases

Covid-19 update GROWING IN CALIFORNIA. NOT GOOD 

Our Covid-19 summer surge is continuing in all state regions, without any sign of slowing. Activity is higher now than it’s been in about a year. The rise is resembling last year’s summer surge, though shifted a bit later into the summer.

The 2026-27 vaccine is available in pharmacies and clinics across the state. If you haven’t had a shot or infection in the past four months, and you’re at higher risk for serious infection, I recommend putting the vaccine on your to-do list.

Flu, and the new mRNA vaccine

Flu activity remains very low in California, but I’m keeping my eye on some early season stirring. The timing would be right for the tiny upticks that precede the full onset, usually in November.

If you’re planning to get a flu shot this season (and you should) and you’re over age 50, you have a new choice to make between a newly available mRNA vaccine (mFLUSIVA), or the traditional formulation. Some of you have asked for guidance.

First of all, either is far better protection than no shot. For me, I’m leaning toward the mRNA vaccine, and here’s why.

Safety. The mRNA vaccine has been tested in roughly 40,000 people in clinical trials. The studies compared the mRNA vaccine with the traditional vaccine. The rate of serious reactions was very low, and essentially the same, for both. People who got the mRNA vaccine had more of the unpleasant effects many of us experienced with mRNA Covid shots—a sore arm, fatigue, headache, and generally feeling under weather on the day after the shot.

I didn’t feel terrible after my mRNA Covid-19 shots, and this informs my flu shot decision. Friends who felt completely laid out by other mRNA shots are feeling differently, and opting for the traditional flu shot. This is totally reasonable for quality of life.

Effectiveness. The mRNA flu shot was about 27% more effective at preventing confirmed flu illn a traditional, regular dose, flu vaccine.

It also produced a stronger immune response than the higher dose traditional vaccines recommended for adults 65 and older. That promising data led to accelerated FDA approval that expedites access to the shot for that high-risk group.

An unknown. No study has compared how well the mRNA shot prevents clinical illness against the high-dose flu shots recommended for people age 65 or older. Blood tests of study participants showed that the mRNA vaccine produced more flu-fighting antibodies than the traditional high-dose vaccine. This flu season we’ll see if that lab result translates into actually preventing more illness for this group.

Availability. California health insurers must cover vaccines recommended by the California Department of Public Health—supported by the West Coast Health Alliance—at no cost and without prior authorization. That should include the new mRNA flu shot as it reaches pharmacies. Still, mFLUSIVA is only reaching “select retailers” so far. If your pharmacy doesn’t have it, don’t wait too long. The performance of the various shots is enough of a toss up, at this stage, to take what’s offered. Any shot beats no shot at all.

That’s all for now. I’ll connect next week from New York!

Love,

Matt

Dr. Matt Willis is the author of Your Local Epidemiologist in California. A California native, he has served as a primary care physician, CDC epidemiologist, and public health officer for Marin County, where he guided the pandemic response. He lives in Marin with his family and their dogs, Teddy and Ramona.