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Enjoying this newsletter? Why not share it with a friend? Joy is contagious. Also: mosquitos, infant botulism, H5N1, peak tick season, and more.The Dose (June 16)
I’m not a big basketball fan, but boy, the sound of Manhattan at the final buzzer of the NBA Finals was electric in every video I came across: cheering, weeping, horns honking, singing, hugging, cigars being lit, an utter unselfconsciousness, pure and absolute jubilation. It gave me goosebumps. It’s a reminder that joy is contagious. Congratulations, New Yorkers, and thank you for the reminder of the value of community and shared joy. More of that, please. Speaking of shared joy, the World Cup has officially kicked off, and we are here with what the health data show. We’re also at peak tick season, and mosquitoes and infant botulism have entered the chat. Other low-risk but high-consequence things are happening, including bird flu heating up among cows again. And pediatricians are getting bombarded with vaccine questions. We answer the latest and update a resource for you. Here’s what’s going on and, most importantly, what it means for you. Disease “weather” reportWe are at peak tick seasonAcross much of the U.S., we’re in the heart of tick season. After starting earlier than usual, it’s now tracking close to previous years. I’m hopeful we’ll see activity taper off over the coming weeks. What this means for you: It’s still important to enjoy the outdoors, so prevention is the name of the game. Use an EPA-approved repellent, wear long pants when possible, and do a quick tick check afterward. The vast majority of ticks don’t carry diseases, but regardless, the sooner a tick is removed, the lower the risk of transmission. Mosquito season is hereMosquito season is ramping up across much of the country. We can expect mosquito-borne diseases to peak in August or September. Why? Mosquitos are cold-blooded, so transmission is a bit like a chemistry experiment. If it’s too cold (below ~16°C or ~60°F), the mosquito life cycle slows down too much to spread disease. Closer to the “magic temperature” of ~25°C / ~77°F, mosquitoes are happier and diseases spread a little more easily from mosquito to human. West Nile is the leading cause of mosquito-borne disease in the U.S. It is a fairly new disease—25 years ago, we didn’t have it around. But it is very rare. So far this year, we’ve seen only 13 cases of West Nile. (In June 2025, we had 62 total and August had the most cases at 958) What this means for you: Your risk depends on geography and other factors, including older age. As mosquito populations grow, it’s worth dusting off the bug spray and clearing standing water around your home. Low risk to you, but disease of high (and potentially) consequenceSeveral outbreaks are on my radar, but all remain very low risk to the general U.S. public:
Cumulative Ebola cases in first 100 days of outbreak declaration. Markers are values from WHO/CDC/ECDC situation reports. Figure by Your Local Epidemiologist
H5N1 dairy herds. Purple: updated figure with USDA numbers since CDC figure has only been updated since June 3. Source: CDC and USDA. Healthy CupThe World Cup has officially begun, and the good news is that there have been no significant health events so far. Overall health risks remain low, but we’re watching three signals:
Good newsWe can always use it. Three today:
New World screwworm detections by county. Figure from a dashboard created by Genompic Epi.
Question grab bag“This week I have encountered several patients saying “vaccines are only studied for 5 days.” Can you update your 12 questions about vaccines handout to address this succinctly? It would be very much appreciated. – A tired pediatrician.” This is a common rumor. That figure comes from a line in the package insert describing the short window when vaccine trial participants fill out a daily diary card (see below for an example). But that card is only tracking the expected, short-lived reactions to a vaccine (sore arm, redness, fever, fussiness), which are caused by the immune response itself and reliably fade within a few days. Symptoms that persist longer usually point to a different cause, like an unrelated infection picked up around the same time, so that brief window is all the diary card needs to cover.
Chart from Appendix 3 here has an example showing what these look like. But vaccine monitoring doesn’t stop there. The same trials track other health events for months to years, recorded as they happen rather than on a checklist. And for routine childhood vaccines, those original trials are now just the starting point: we have real-world safety data on hundreds of millions of children across decades, consistently showing that the benefits far outweigh the risks. We’ve updated the FAQs for paid subscribers, with the latest is available below. Thank you for all your effort, and all clinical care teams on the front line.
Bottom lineSummer brings its share of bugs and outbreaks to watch, but the risks to you are low with a few simple precautions. Don’t let the worry crowd out the shared joy. Love, YLE Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below |
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