One Year In

Looking back and forward at YLE CA

YLE California is turning 1! Man that went fast. When I first hit “publish” on on August 14, 2025, I had no idea what to expect. I felt sure about getting the science right, but wasn’t sure anyone would be listening and engaging on the other end.

Katelyn (Your Local Epidemiologist) and I decided to give it a year, and than ask two questions: is the newsletter valuable to you, and is it sustainable. We knew we’d learn a lot, and that it wouldn’t be easy to build a community and audience in this saturated information landscape.

Value: This question isn’t mine to answer, it yours. It’s been reassuring to watch the numbers rise week to week— we’ve grown to over 30,000 subscribers, and about 100,000 followers. We’re a Substack best seller.

But YLE is more about quality than quantity. Our goal is to build an engaged community-- and your messages, comments, and emails tell me we’re meeting a need for information you can use. Thats the kind of value we’re looking for. That’s way more important than the numbers. Those exchanges also taught me how I can better support you.

Four lessons I’ve learned from you

Jump in early. When a new public health problem is first emerging – think hantavirus, or cyclospora, another Covid-19 wave– things are usually uncertain, facts and rumors are entangled, and the media is usually taking the ball and running. It can be confusing and alarming. Sometimes I’m not sure when to enter those waters with a post, because it’s impossible to be first on the scene and be certain.

I tend to jump in early, and you’ve assured me you see that as valuable, and as a YLE CA sweet spot. To step back and take a breath, to see what we do and don’t know, what to keep an eye on, and what you can do to stay safe. All from the California angle. I have the freedom to do that, trusting you know we’re learning as we go, and that guidance may change.

Be brave: You’ve taught me to be a brutally honest scientist. For years I wrote policy documents— cautious, distant, slow, top-down— from inside government. There wasn’t much room for first-person, for opinion, for “I’m not sure yet.” YLE CA lets me bring my expertise in my own voice: to say what I think, to be transparent about where the evidence is thin, to write from curiosity, and bring you along.

Keep the mix. I’ve covered over 200 topics in 60 posts. I wasn’t sure if that was going to be too broad, but I’ve heard you appreciate the range. One way I pick topics is to think “What’s happening right now in California that can impact our health, and what information would be most helpful to the YLE community?” That explains why you find updates on outbreaks and wildfires next to healthcare access changes and breakthroughs in science. I also sprinkle in some good news, and celebrate those working on the front lines.

Place matters: You’ve been clear you value the state focus. I feel lucky to write for the state I know and love, and I see where we’re really our own health ecosystem. California has become a leader in the fight against federal attacks on public health and science. For every national story, from outbreaks to health policy changes, there’s a California version— and ours is often different in very good ways. Higher vaccination rates have meant fewer measles cases. State lawmakers sue to block federal funding cuts. New state laws break ties to faltering federal agencies.

Of course our state health system could be a lot better, within what our leaders have control over. I’m not afraid to call that out, and elevate opportunities for change. We have policymakers who actually read this stuff, and a public engaged enough to argue back. That’s made writing about public health here as exciting as it was to practice it.

Ask

We need your help. I wanted to use this anniversary to tell you what this year has taught me, to thank you for being a part of this community, and to ask you for your help. It’s still a leap of faith, but one that’s worth it. As a public health guy, I’m used to making decisions when things are uncertain. But in order to continue to do the work I love, YLE CA needs more financial certainty.

I’m never comfortable asking for financial support, but none of this works without it. The kind of independent, accountable science communication I do takes time to do well, and it’s gotten harder to sustain. This newsletter is funded by paid subscribers. While subscriptions are growing, we need more paid subscribers to keep the lights on at YLE CA. Please upgrade below.

Bottom line

This is different work than anything I’ve done before. After years as a physician, an epidemiologist, and a health officer, being a health communicator helps integrate those chapters. Bringing that history and perspective together has been incredibly rewarding.

One of the best surprises of this year was seeing that the kind of relationship I had with patients, and with my community as health officer, extended to YLE CA, with people I mostly can’t see. The connections are real, and have helped us through some dark days for public health and science.

In my first post I promised “science-based health guidance that you can use”. I’ve been learning from you what that looks like. As we start into year two, I’m renewing that promise. Thank you for spending a year with me, and I hope you can help make the next one possible.

Love,

Matt

Dr. Matt Willis is the author of Your Local Epidemiologist in California. A California native, he’s 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.