New York has a very full week ahead: a major heat wave, Fourth of July events, World Cup crowds, and a blood emergency across the state.

So for this week’s Dose, I’m covering how to stay cool, how to help your community and your hospitals stay ready (including an exciting YLE event—more details below), and an update on community health as New York navigates the World Cup.

YLE will also be taking a summer break next week to recharge, so there will be no newsletter.

Let’s get into it!

A heat wave arrives—here’s how to stay safe during the holiday weekend

A heat wave is expected to hit the Northeast, including New York, starting Wednesday, July 1 and lasting into the Fourth of July weekend. Some are saying this will be the hottest we’ve seen since 2012.

Heat is the deadliest weather hazard in the U.S., and unfortunately, it’s becoming deadlier in New York. Last year, record breaking heat resulted in the deaths of 19 New Yorkers in NYC over a four day heat wave in June. And it can feel worse in the city—NYC’s urban heat island effect can push city temperatures 5–10°F hotter than surrounding suburbs.

This summer, because of the World Cup, fan zones, fireworks shows, and other large events throughout the city, more people may be exposed, many of whom may not be accustomed to these kinds of heat waves.

Here’s what you need to know.

Every year, thousands of people across New York visit the emergency department (ED) for heat-related illness. In 2025, there were 4,007 heat-related ED visits in New York state, excluding New York City—above the average for the previous four years. From May 1, 2026, through June 28, 2026, there have already been 1,144 ED visits for heat in New York state (excluding NYC), which is right at the average for the previous four years.

The effects of heat aren’t felt uniformly. In NYC, the Bronx and Brooklyn are historically the hardest-hit boroughs due to issues like more limited access to air conditioning and less tree cover, which can compound the danger.

Counterintuitively, people in New York who die from heat stress are most often exposed to dangerous heat inside their homes, not outside. Without air conditioning, indoor temperatures can be much higher than outdoor temperatures, especially at night, and can remain elevated for days after a heat wave.

Over the past several years, the majority of heat related deaths in NYC either did not have AC or it wasn’t working. This means that having a working AC and using it prevents in-home heat related death.

Overall, the best thing to do is to try to stay cool and check in on elderly neighbors, relatives, or anyone you know without air conditioning or who may not be using it. At YLE National, we covered the top five things we’ve learned about managing heat, and here are a few more tips that I’ve found helpful.

• Know your risks. The CDC and National Oceanic and Atmospheric Administration (NOAA) dashboard tracks local heat risk scores that takes into account temperature, humidity, and other metrics that impact health. The risk score ranges daily from “No risk” to “Extreme” heat risk. Enter your zipcode here.
• Use a cooling or water space. Cooling centers can be found in NYC here and across the New York state here. Libraries, museums, or coffee shops are great options. In the City, public schools, city buildings, Health Action Centers, and Overdose Prevention Centers are also opening as cooling zones (call 311 for the nearest one), and NYC Health & Hospitals is operating cooling vans. Public pools and water spray areas are also great options in the City (Cool It! NYC) and across the state.
• Keep your pets cool. They’re susceptible to heat stroke, too. Here are hot-weather safety tips for pets, including knowing the symptoms of pets overheating, checking the sidewalk for hot pavement, and never leaving pets alone in cars.
• Understand when fans are useful and when they can cause harm. When it’s humid, fans continue to help by speeding up sweat evaporation. When it’s dry heat and above 95°F, fans can circulate hot air towards your body, actually causing you to gain heat.
• Watch out for hot playgrounds. Metal, turf, and black asphalt can cause burns on hot days.
• Know the symptoms of heat-related illness. Confusion, dizziness, hot dry skin, and unconsciousness are serious signs of heat stroke that warrant calling 911.

To cope, this week I’m moving my runs indoors on the gym treadmill, checking out what’s playing at my neighborhood theater, and have already stocked up on my favorite ice cream (Salt & Straw’s mint chip anybody?!). Try to stay sane out there with the heat this week!

New York is facing a blood emergency this month—your donation matters

New York State blood centers declared a formal blood emergency on June 12, 2026. Statewide supply dropped below two days of blood overall, and below one day of Type O blood in some areas. Types A-, B-, O+, and O- are all at dangerously low levels; O- is the universal donor type used in emergencies when a patient’s blood type is unknown

Why this matters:

Emergency responders sometimes refer to summer as ‘trauma season,’ because we see increases in severe injuries from car accidents, ATV crashes, sports-related injuries and other summer activities. Hospitals need blood ready before those patients arrive. For example, a single serious car accident victim can require up to 100 units of blood.

National data show someone in the U.S. needs blood every two seconds, and nearly 29,000 pints are required daily. And it’s not just emergencies—childbirth, surgeries, cancer treatment, and chronic disease management (like for sickle cell anemia) also depend on a steady blood supply. If hospitals don’t have enough blood on hand, clinicians may need to make hard decisions about who gets blood transfusions and who has to wait.

The challenge is that blood is perishable. Red blood cells last 42 days and platelets only five days. Summer holidays and travel also often mean that fewer people donate. Even without these seasonal challenges, only about 3% of age‑eligible Americans give blood each year.

And this year, the stakes might be higher than usual. With NYC hosting the FIFA World Cup and America’s 250th anniversary celebrations this summer, millions of additional visitors mean more people at risk for traumatic injury, and more strain on local blood supplies.

One donation can help up to three people, and you’re eligible to give every 56 days.

What to do: Donate blood through a month-long YLE virtual blood drive this July, with in-person meet-ups in August for participants! Schedule an appointment for YLE’s campaign here. I was able to schedule one easily, and have already started planning to eat iron-rich foods leading up to it.

If every one of our 40,000+ subscribers donated a pint of blood, we would support almost three weeks of blood needs across New York state.

All blood types are needed, but types O-/O+, A-, and B- are especially needed. Find your nearest site at nybloodcenter.org or redcrossblood.org. If you donated in the last 56 days, share this with someone who hasn’t.

World Cup updates

With World Cup events bringing more visitors, crowds, and international travel through New York, I’m keeping an eye on the usual public health signals.

So far, there’s no sign of a disease increase tied to World Cup activity. That’s good news. But it doesn’t mean public health is “off duty.” There’s a ton of behind-the-scenes monitoring happening, especially when people are traveling from all over the world.

The biggest thing on my mind right now is what the effects of the heat wave will be this week. Many of the million extra visitors in NYC here for the World Cup and other major events may not be accustomed to New York heat waves. This could show up in heat-related ER visits, and I think will be a test-piece for the public health system during the World Cup.

Thankfully, on the infectious diseases front, things are quiet.

Respiratory illnesses are, for the most part, low and staying down: There have been no observed increases in hospitalizations for Covid, flu, or RSV.

It looks like there’s some mild cold going around. I have several friends who are reporting some cold symptoms, and test positivity shows that there’s a decent amount of enterovirus or rhinovirus (both of which cause the common cold).

West Nile Virus: data is now being shared by the NYC health department, and so far it’s showing up in Queen and Staten Island. I haven’t seen any data on human infections yet, but I’ll cover when it’s published. When West Nile Virus really picks up, local health deparments may conduct aerial spraying of insecticides via planes or helicopters to reduce the mosquito population. Currently there are no spraying events scheduled in NYC.

Ebola: JFK airport also continues to screen travelers returning from the Democratic Republic of Congo and Uganda for Ebola. Travelers from these countries are being asked to monitor for symptoms for 21 days after arrival. So far, no infections have been detected in NYC. That’s good news and a reminder of what public health looks like when it’s working quietly in the background.

Bottom line:

As we head into the heat and the holiday weekend, remember to stay cool, check on someone without air conditioning, watch out for symptoms of heat illness, and donate blood if you can.

And happy Fourth of July, and happy 250th birthday, America!

Love,

Your NY Epi

Dr. Marisa Donnelly, PhD, is an epidemiologist, science communicator, and public health expert. This newsletter exists to translate complex public health data into actionable insights, empowering New Yorkers to make informed and evidence-based health decisions.