Outbreaks
Disease Outbreaks
Outbreaks of vaccine-preventable diseases can happen in communities with low vaccination rates when an infected person spreads the disease to others. An outbreak occurs when there are more cases of a disease than normally expected within a certain geographic area, time period, or population.
Thanks to vaccines, many diseases that used to be common in the U.S. (like whooping cough, measles, and polio) are thought to be a thing of the past. Unfortunately, many communities are now seeing outbreaks, especially where vaccination rates have gone down.
While preventable diseases may not be circulating in your community, they exist around the globe in places where people don’t have access to vaccines or are not getting vaccinated. Most of the time, a disease is introduced to a community from somewhere else, brought in by someone who may or may not know they are sick.
To avoid being patient zero in an outbreak, check to be sure you have all of the recommended vaccines and are aware of any outbreaks before traveling.
Vaccines Stop Measles from Spreading
Measles is very contagious. Exposure to an infected person with measles will cause infections in 9 in 10 people who are not protected. Measles is serious and can be deadly, even in otherwise healthy children.
Recent Outbreaks
- Measles: There are multiple active measles outbreaks in the United States (the largest in Texas), with 935 confirmed cases and three confirmed deaths so far. Experts warn that the actual case counts may be much higher. Get the latest on measles outbreaks, and make sure your family is up-to-date on MMR vaccination to prevent measles.
- Whooping Cough: So far in 2025, there are more than double the number of cases of pertussis, or whooping cough, as in the same time period in 2024. Two infants have died this year as of April 2025. Stay up to date on whooping cough, and make sure your family is up-to-date on DTaP (for children) and Tdap (for preteens, pregnant women, and adults) vaccines to prevent whooping cough.
- COVID-19: The COVID-19 pandemic is an example of a disease outbreak that quickly turned into a global pandemic as travelers carried it around the globe before communities had any protection from vaccines or prior infection. COVID-19 continues to circulate, so make sure your family is up to date on COVID-19 vaccination.
- Mpox: An mpox outbreak in the United States occurred during 2022-23. By May 2023, the Centers for Disease Control and Prevention (CDC) reported a total of 30,395 cases and 42 mpox-associated deaths, with most cases occurring in communities of men who have sex with men. Cases have since declined thanks to vaccination campaigns, behavioral changes within at-risk communities, and public health interventions.
When an outbreak is declared, each sick person must be evaluated to see if their illness is part of the outbreak. Since each outbreak is unique, the Centers for Disease Control and Prevention (CDC) creates a definition of the typical sick person. If someone is ill but doesn’t fit the definition, they will most likely not be counted as sick due to the outbreak.
When healthcare professionals are determining if a sick person fits the outbreak definition, they will ask themselves questions such as:
- Does the person fit the population (age, vaccination status, risk factors, etc.) most affected?
- Did the person get sick in the place or season where the outbreak is occurring?
- How long did it take for the person to get sick from exposure to the disease?
- Does the sick person have the features of the disease?
When cases pop up, they are investigated according to the definition and categorized as “confirmed” (definitely a case), “probable” (likely a case), or “suspected” (maybe a case).
This definition is essential in determining which cases are part of the outbreak and give officials important data that are necessary to contain the outbreak.
You can find information about disease outbreaks in the United States and internationally on the CDC’s Outbreaks web page.
When deciding to travel nationally or internationally, check the CDC’s Destinations web page to see which vaccines you may need in order to avoid getting sick and bringing disease back into your community.
Plan ahead when traveling and make sure you get all of the necessary vaccines at least two weeks before travel. You can find out which vaccines you need on CDC’s Traveler’s Health web page.
Measles is causing worrisome outbreaks across the globe. Due to outbreaks in the United States, check Measles Cases and Outbreaks web page weekly for information on measles outbreaks and cases in your area. It’s essential to get vaccinated against measles, as the highly contagious disease is preventable with a very effective vaccine.
If you suspect you or a family member in your home may have a vaccine-preventable disease, please stay home, call your healthcare provider, and follow instructions. If you don’t have a healthcare provider and you believe you have a disease that’s part of an outbreak, call the number for your local health department.
Vaccines need to be given before there is disease circulating in the community because it can take a few weeks for the body to become immune. Children should be vaccinated according to the recommended schedule before they enter school and should be vaccinated into adulthood to avoid terrible consequences from vaccine-preventable diseases.
Adults need vaccines, too. Be diligent about keeping you and your family up to date on vaccines.
By the time an outbreak has occurred, it will be too late. Don’t wait to protect yourself and your family from vaccine-preventable diseases.
To prevent an outbreak, enough people in an area need to have immunity, which can be achieved through vaccination. The more people who are vaccinated, the more difficult it is for the disease to spread. If enough of the population is immune to a disease, people who are not vaccinated due to medical reasons, age restrictions, or by choice are better protected. This is called community immunity.
You can help prevent outbreaks and sickness in your family by ensuring your entire family is up to date on their vaccines. Check out the following recommended vaccine schedules and talk to your healthcare provider about which vaccines you and your family need to get to be up to date on vaccines.
