Before summer travelers leave home, health experts have a reminder that has nothing to do with the record heat in Europe and the U.S.: Make sure your vaccinations are up to date.

Although polio has largely receded from public health concerns in the U.S., where it was eliminated more than four decades ago, strains of the virus that causes the disease still circulate in parts of Europe, Asia and Africa. At home, measles outbreaks have recently been reported in Pennsylvania, Virginia and Utah, pushing the total number of cases in the U.S. during 2026 to more than 2,220-already more than last year's count, according to the Centers for Disease Control and Prevention.

"More than anything, it's a good reminder that staying up to date on vaccinations is critical to staying safe and healthy while traveling," said Michael Ben-Aderet, MD, associate director of Hospital Epidemiology at Cedars-Sinai.

The Cedars-Sinai Newsroom spoke with Ben-Aderet about what travelers should know about polio and measles and how to stay safe this summer.

Where does polio still exist?

Polio is caused by a highly contagious virus that has essentially been eliminated from most of the world through vaccination. Wild strains still persist in a handful of countries, including Afghanistan and Pakistan, which means the vast majority of international travelers are at relatively low risk, particularly if they've been vaccinated. In recent years, roughly 30 countries in Africa, Europe and Asia, including the U.K. and Germany, have shown signs of the virus circulating. However, those signs are not necessarily tied to outbreaks. For example, public health officials in the U.K. have detected the virus in wastewater tests, which likely points to some degree of asymptomatic polio.

How does polio spread?

The poliovirus typically spreads when an infected person doesn't wash their hands after using the restroom and contaminates water, food or other surfaces that others touch. It usually causes a mild illness that most people recover from quickly. What makes polio historically frightening is that a small percentage of infections can progress to paralysis, typically affecting the legs and feet, when the virus invades the nervous system. That's why vaccination is so important. It has essentially eliminated that fear in populations where immunization rates are high.

How big of a threat is polio to international travelers?

Almost everyone in the U.S. received the polio vaccination series as a child. For vaccinated travelers, the risk is minimal. For older adults concerned that their immunity may have waned over the years, a booster is worth considering before visiting regions where polio transmission remains a possibility. The polio vaccine has minimal side effects, so there is little harm in getting the vaccine. You won't receive the full benefit of immunity until four weeks after vaccination, but you'll start receiving some protection immediately.

Where is measles a concern?

Measles is, in many ways, a more immediate risk to summer travelers, especially in crowded or enclosed spaces. It's far more contagious, spreading through airborne particles from an infected person's cough or sneeze, and it can stay in the air for up to two hours after that person leaves.

Recent clusters have emerged in parts of California, Texas and Oklahoma, and the largest outbreaks have been reported in India, Bangladesh, Yemen, Mexico and Pakistan. Measles outbreaks are happening in multiple countries throughout the world. You could try to avoid known measles outbreaks as you travel, but the chance of encountering someone with measles has risen as fewer people get vaccinated, and you don't know when you'll be exposed.

How protected are those who have been vaccinated?

Most fully vaccinated individuals are well protected for life. Adults who are uncertain whether they ever received the two doses of the MMR vaccine, which protects against measles, mumps and rubella, should consider getting at least one dose. Adults at high risk should consider two doses at least 28 days apart. Children are recommended to receive two doses: one at 12 to 15 months and one at 4 to 6 years old. Babies 6 to11 months old should get one dose before they travel and two more doses after their first birthday.

It's always a good idea to check your vaccination records and to consult your primary care provider or a travel medicine clinic four to six weeks before traveling abroad.

Read more from Cedars-Sinai Stories and Insights: 8 Expert Tips to Avoid Getting Sick When You Travel