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Overseas Security Advisory Council
Bureau of Diplomatic Security
U.S. Department of State

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CDC’s New COVID-Specific Travel Health Notices


On November 21, the U.S. Centers for Disease Control & Prevention (CDC) augmented its Travel Health Notice system with a four-level scale focusing specifically on COVID-19, as well as new recommendations regarding testing and international air travel for travelers. These recommendations, which you should consider alongside existing CDC travel health guidance, provide the best information to help inform safer, healthier, more responsible travel. Like any other indicator, users should not view this system as an absolute, pulling staff and cutting programs the moment a level increases, or restarting things the moment they decrease. Rather, OSAC encourages private-sector and private-citizen travelers alike to incorporate the information in this system into their travel security protocols (with the help of the OSAC Risk Matrix) alongside other indicators such as those in State Department Travel Advisories, OSAC Country Security Reports, and foreign government security assessments, and those from any other reliable source. This report will focus on the changes to the CDC Travel Health Notice system, explaining how the CDC assigns levels to any one destination, and noting how security managers can best make use of them.

CDC COVID-19 Travel Health Notices

CDC Travel Health Notices (THNs) inform travelers and clinicians about current health issues in destinations around the world. The existing CDC THN levels are as follows: Watch Level 1 (Green) notes travelers should practice usual precautions for a given destination, as described in the Travel Health Notice and/or on the CDC’s country destination page, which outlines all of the health issues the CDC is watching in a given location. This includes being up-to-date on all recommended vaccines and practicing appropriate mosquito avoidance where applicable. Alert Level 2 (Yellow) encourages travelers to practice enhanced precautions, describes additional precautions, or defines a specific at-risk population. Warning Level 3 (Red) urges avoiding all non-essential travel to a given destination due to an outbreak that poses a high risk to travelers, and a potential lack of available precautions to protect against the identified increased risk. These three levels touch on all health issues, other than COVID-19, and will remain in effect.

The new four-level system is specific to COVID-19 and details the levels of COVID-19 in international destinations as well as U.S. territories. Travel Health Notices primarily indicate the incidence rate and trajectory of virus cases. The CDC reviews data daily to ensure the most up-to-date information to inform travel decisions. The new system incorporates new travel and testing recommendations, is simple to understand, and exists alongside the system focusing on all travel health issues. The four new COVID-19 THN levels are:

  1. Level 1 (Low Level of COVID-19), indicating travelers should practice enhanced precautions;
  2. Level 2 (Moderate Level of COVID-19), advising travelers at increased risk for severe illness from COVID-19 to avoid all nonessential travel;
  3. Level 3 (High level of COVID-19), advising all travelers to avoid all nonessential travel; and
  4. Level 4 (very high level of COVID-19), advising to avoid all travel.

Travelers accustomed to the State Department Travel Advisory system will recognize a change similar to the one the State Department implemented in 2019. In that change, the State Department introduced the idea that Travel Advisories existed all foreign locations, not just the ones with threats. This change made it easier for travelers to low-threat locations to understand the existence of a low-threat environment, rather than relying on the absence of an advisory to reflect the absence of a threat. The CDC COVID-19 THN system will similarly assign those locations with low levels of COVID-19 a Level 1 designation, rather than refraining from informing the traveling public altogether.

How will CDC assign THN Levels?

The CDC is using quantitative methods – data – to assign each location’s COVID-19 THN level. The data the CDC will use to assign the COVID-19 THN level will differ based on the population of the affected area. For places with populations over 200,000, the level will depend on the rate of new cases per 100,000 people over the past 28 days. The level for places with a population of 200,000 or less will depend not on the rate but on actual COVID-19 case counts (cumulative new cases over the past 28 days). See the chart below to note the slight but important differences.

Incidence Rate Ranges for COVID-19 Travel Health Notice Levels
Destinations with populations over 200,000










Incidence Rate

(cases per 100,000 people over past 28 days in a place with a population of 200K+)

More than 100



Less than 5

Case Count

(new cases over past 28 days in a place with a population of 200K or less)

More than 100



Less than 10


The CDC will use hospitalization rates and positive testing rate (over a period of 28 days) as secondary criteria, derived from official sources such as health ministry websites. CDC reviews primary criteria daily.

What about raising or lowering THN Levels?

The CDC will raise a location’s COVID-19 THN level when its primary criteria meet the range of a higher COVID-19 THN level for 14 consecutive days. CDC may act before 14 days if the primary criteria demonstrate a sudden or abrupt increase in COVID-19 levels for 7+ consecutive days instead of the usual 14.

It takes slightly longer for COVID-19 THN levels to decrease, allowing travelers to be sure of the trajectory of the disease. A location is eligible to move to a lower level when it meets the primary criteria for a lower level for 28 consecutive days, which is two full incubation periods. The incubation period is the time it can take for a person to develop infection after exposure to the virus that causes COVID-19. Once a destination meets primary criteria for 28 consecutive days, CDC will review secondary criteria. If hospitalization rates are stable or decreasing, and cumulative testing positivity rates are in line with primary criteria data, CDC will lower the COVID-19 THN level. If secondary criteria are unavailable or are inconsistent, the location remains at its current COVID-19 THN level until reevaluation.

CDC Testing and Air Travel Recommendations

The CDC has issued new recommendations for those traveling abroad. It notes that testing before and after air travel is an important part of reducing the spread of COVID-19 on planes, in airports, and at travelers’ destinations. The new testing recommendations provide travelers and travel partners information on when to get tested before and after travel. 

  • Travelers should get a viral test 1-3 days before and 2–5 days after their flight. Wait for your test results to come back before you travel. If your test result is positive, immediately isolate yourself and follow public health recommendations. Do not travel if your test result is positive.
  • A negative test does not mean that you were not exposed or that you will not develop COVID-19. Make sure to wear a mask, stay at least 6 feet from others, wash your hands, and watch your health for signs of illness while traveling.   
  • Keep a copy of your test results with you during travel. Airport, airline, or other authorities may ask you for them.

Get tested 2–5 days after your flight, and stay home for 14 days after returning from your trip. For travelers with no known exposure to COVID-19, getting tested 1-3 days before travel and 2–5 days after travel can help find infections and control spread where you live. Remember that a negative test does not mean that you were not exposed; you could still develop COVID-19. Watch for symptoms for a full 14 days after travel, immediately isolate yourself if you develop symptoms, and follow public health recommendations. (Note that the CDC recommendations are specifically for those flying internationally to/from the United States, but there is no reason travelers shouldn’t take the same precautions when traveling internationally by other means or without a U.S. departure point or destination.)

Plan ahead. In addition to testing, take steps to limit exposures and avoid higher-risk activities for 14 days before your trip. All travelers with a known exposure to COVID-19 should quarantine, delay travel for 14 days after exposure, test themselves, and monitor their health.

  • Examples of Higher Risk Activities include:
    • Travel from a country or U.S. territory with a Level 2, Level 3, or Level 4 Travel Health Notice;
    • Going to a large social gathering like a wedding, funeral, or party;
    • Attending a mass gathering like a sporting event, concert, or parade;
    • Being in crowds like in restaurants, bars, fitness centers, or movie theaters;
    • Being in airports, or using public transportation; and
    • Traveling on a cruise ship or river boat.

Further Resources

For further information, contact the OSAC analyst for your desired region of travel, and consider the following resources:



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