What are emerging infectious diseases?

Emerging infectious diseases are any of these:

• Outbreaks of new diseases that were unknown before 

• Known diseases that are now spreading quickly in number of cases, or in number of areas where people are sick

• Known infectious diseases that are persistent and can't be controlled

Emerging diseases include:

• Coronavirus infections, such as COVID-19, SARS, and MERS

• HIV infections

• Lyme disease

• Escherichia coli (E. coli) O157:H7

• Hantavirus

• Dengue fever

• West Nile virus

• Zika virus

Reemerging diseases are those that come back after they have been on a major decline. This may happen because of problems in public health actions for diseases that were once under control. They can also happen when new strains of known diseases occur. People’s behavior can cause diseases to reemerge. For example, declines in immunization rates and maintaining correct vaccine temperatures during storage and handling to preserve potency has caused measles to happen again in some areas. The overuse of antibiotics has also caused some bacteria and viruses to adapt to medicines. This means they can’t be killed easily. This has caused diseases that once were controlled and treatable to infect more people.

Reemerging diseases include:

• Malaria

• Tuberculosis

• Cholera

• Pertussis

• Influenza

• Pneumococcal disease

• Gonorrhea

Travelers should know that some diseases under control in the U.S. may be active in other countries. Talk with your healthcare provider before you travel. Ask if you need vaccines, medicines, or other safety steps before travel.

Who is at risk for emerging infectious diseases?

Traveling to other countries can put you at risk for infectious diseases that are not common in the U.S. Travelers who get ill in a country where treatment for these diseases may be limited are even more at risk. All people planning travel should learn about the health risks of the countries they are traveling to. Learn how to reduce your risk of getting these diseases.

Why are travel-related infectious diseases on the rise?

Researchers think that more global travel is why many infectious diseases not active in the U.S. come back and infect more people in the U.S. The number of people who travel to other countries increases every year. More people now take trips to remote parts of the world. These areas often have health problems not common in the U.S. They may also not have enough healthcare services. Many travelers may not know the health risks active in other countries. These people may not take the safety steps before they travel. These include getting vaccines or taking medicine that can prevent illness.

Many of the newly-found infections have existed for a long time. But healthcare providers have not seen them in areas where new outbreaks happen. Today, people can travel anywhere in the world within 36 hours or less. Because of this, infections that were rare before can quickly spread to areas where they didn't occur.

How can travelers reduce their risk from infectious diseases?

Travel abroad doesn't need to result in an illness from infectious diseases. Taking these steps can help reduce your risk:

• Get travel health information as far before your trip as possible. Do this even if you have been to the destination in the past. Health conditions can change quickly in some parts of the world. Learn about special risks for children, pregnant women, people with chronic diseases, and people with weak immune systems who might be traveling with you.

• For specific advice, see a travel medicine specialist or a healthcare provider who knows the area you will visit. Do this at least 4 to 6 weeks before your trip. If you are pregnant or plan to get pregnant, ask a travel medicine specialist about pregnancy health risks in your travel area.  

• Make sure your routine vaccines are up-to-date. This includes the yearly flu vaccine. 

• Get the vaccines and take the preventive medicines advised by your healthcare provider. You may need some of these weeks before travel. Contact your healthcare provider as soon as you have travel plans. This will help make sure the vaccines medicines can help you.

• If you need to take medicine to prevent malaria, take it as prescribed. Follow dosage instructions carefully. Medicine to prevent malaria must be started before your trip. This is to make sure there is enough medicine in your body before you have contact with mosquitoes at your destination. Check with your healthcare provider or pharmacist to be sure you start them early enough. You must keep taking them during your trip. And you must keep taking them for a precise number of days after you return. The amount of time depends on which medicine you take.

• Put together a traveler's first aid kit. It should have items targeted for where you will travel. Add enough extra medicines and supplies to last a few days past the planned end of your trip. Your healthcare provider can help you figure out what should be in your kit.

• Bring personal protective equipment with you to prevent COVID-19 throughout your travel. This includes at least masks and alcohol-based hand sanitizer. Depending on the level of potential exposure, you may also want to bring an eye shield or goggles, a personal respirator, medical gloves, and protective gowns.

• Before you leave home, research how emergency medical care is done where you’re going. Find out what medical evacuation services are available in case of serious illness. Contact your health insurance plan. Ask them what is covered in other countries. Take two copies of your medical insurance information with you. Keep each copy in a separate place. If you are traveling as part of an organized tour, ask the tour company what medical services are available on the trip. Ask if they offer additional travel health insurance.

• If you have any symptoms of illness when you get home, contact your healthcare provider right away. Tell them where you have traveled. Tell them what symptoms you have. These may include fever, rash, joint pain, diarrhea, belly pain, or red eyes. Or you may have other symptoms.