Health Care Workers, Including Public Health Researchers & Medical Laboratorians

CDC Yellow Book 2024

Travel for Work & Other Reasons

Author(s): Henry Wu, Eric Nilles

Health care workers practicing outside the United States face unique health hazards, including exposure to infectious diseases associated with patient contact or handling clinical specimens. Any type of health care worker (e.g., ancillary clinical staff, nurses, physicians, public health personnel, researchers, students and trainees on international rotations) working in clinical areas or handling specimens can be at risk (see Box 9-01).

Infectious agents can be spread through contact with blood, bodily fluids, respiratory secretions, or contaminated materials or surfaces. Health care workers might be exposed through dermal, ingestion, inhalation, or percutaneous routes of absorption. Risks vary depending on assigned duties, geographic location, and practice setting. Of note, health care workers working abroad can be at increased risk for exposure to patients with emerging, highly pathogenic, or uncommon, infectious diseases (e.g., Ebola virus disease, Middle East respiratory syndrome [MERS], or extensively drug-resistant tuberculosis [XDR-TB]).

Box 9-01 Risks for health care workers practicing outside the United States

  • Challenging practice conditions (e.g., extremely resource-limited settings, natural disasters, or conflict zones) can prevent health care providers from adhering to standard precautions.
  • Greater prevalence of transmissible infections (e.g., hepatitis B virus, hepatitis C virus, HIV, tuberculosis) with potentially increased transmission risk from untreated source patients.
  • Less stringent safety regulations or infection control standards.
  • Limited availability of personal protective equipment (PPE), safety-engineered devices, or postexposure management resources.
  • Unfamiliar practice conditions, equipment, or procedures.

Box 9-02 Health care workers in extreme circumstances

Health care workers regularly provide care in a range of extreme circumstances, which can be characterized by limited or absent medical and public health infrastructure; lack of fundamental hygiene supplies (e.g., soap and water for handwashing); increased infectious disease transmission; extreme environmental conditions; and high levels of violence. In 2020, 484 attacks against aid workers were reported; 117 were killed.1

Because of the increased risks and consequences of severe disease or injury, adequate prevention and preparation are essential. Health problems for the health care worker can have serious implications, both for the person and for those who depend on the health care worker for provision of health care. Detailed instructions on how to prepare for travel or work in developing countries or humanitarian environments is covered in other sections, but additional key considerations for health care workers include the following:

RELIABLE COMMUNICATION EQUIPMENT, usually a satellite phone, ensuring service provider contract for duration of the mission. Consider portable solar recharging capabilities unless guaranteed a power supply, which is rare in most extreme circumstances.

EVACUATION INSURANCE AND A PLAN FOR ILL OR INJURED WORKERS. Not all deploying organizations provide evacuation insurance (see Sec. 6, Ch. 1, Travel Insurance, Travel Health Insurance & Medical Evacuation Insurance) or a detailed evacuation contingency plan. Both are critical, and the health care worker should be familiar with all details.

WORKERS’ UNDERLYING HEALTH CONDITIONS. Monitor the provider’s health closely, and initiate treatment early, if necessary. Any indication that a potentially serious condition is not responding to treatment should warrant rapid planning for potential medical evacuation.

WORKER PSYCHOLOGICAL STABILITY. Providers in conflict and disaster zones typically work long hours under dangerous conditions and are exposed to profound suffering. These experiences can be intensely stressful, leading to increased rates of depression, posttraumatic stress disorder, and anxiety (see Sec. 2, Ch. 12, Mental Health). Before deployment, providers should think about coping strategies and, as much as possible, stay in contact with a support network of family and friends.

CHEMICAL WARFARE AGENT ANTIDOTES. Although rare, health care workers could be exposed to chemical warfare agents while caring for patients. If exposure to these agents is a possibility, antidotes (e.g., atropine) should be immediately available.

1Source: Impunity must end: Attacks on health in 23 countries in conflict in 2016. Safeguarding Health in Conflict Coalition [PDF]; 2017.

Pretravel Vaccination & Screening

Before traveling or working abroad, all health care workers should be up to date with their routine age-appropriate vaccines, vaccines recommended for employment in health care settings (see Box 9-03), and coronavirus disease 2019 (COVID-19) vaccines. In addition, ensure health care workers receive vaccinations specifically indicated for the country visited. Cholera vaccine, meningococcal vaccine, and inactivated polio vaccine (given as an adult booster dose) could be indicated for health care workers traveling to locations experiencing high incidence or outbreaks of these diseases.

Box 9-03 Recommended vaccinations or documented immunity for employment in health care settings abroad

  • Coronavirus disease 2019 (COVID-19)
  • Diphtheria
  • Hepatitis B
  • Influenza
  • Measles
  • Mumps
  • Pertussis
  • Rubella
  • Tetanus
  • Varicella

Ebola Virus Disease

Consider vaccinating health care workers responding to Ebola virus outbreaks with the Ebola vaccine approved for use by the US Food and Drug Administration (FDA). See also Ebola Vaccine: Information about ERVEBO.

Hepatitis B

Because hepatitis B immune globulin (HBIG) and urgent hepatitis B virus (HBV) infection testing might not be available in resource-poor or field practice settings, be certain traveling health care workers have documentation of post-vaccination antibodies to HBV. Health care workers without documented response to vaccination should receive ≥1 additional dose of hepatitis B vaccine and further serologic testing to assess response.

Hepatitis C & HIV

Pretravel baseline testing for hepatitis C virus (HCV) and HIV infection is not routinely recommended; consider performing baseline testing for people who will be working in areas with high incidence of disease where reliable testing will not be available locally in the event of an exposure.


The Centers for Disease Control and Prevention (CDC) recommends screening for latent tuberculosis infection (LTBI) with tuberculin skin test or interferon-γ release assay for US health care workers; baseline screening is particularly important for health care workers traveling to countries with greater TB transmission risk, or working in high-risk settings (e.g., health care facilities, prisons, refugee camps). For more details, see Sec. 5, Part 1, Ch. 22, Tuberculosis, and Sec. 5, Part 1, Ch. 23., . . . perspectives: Testing Travelers for Mycobacterium tuberculosis Infection.

For people without a documented history of LTBI, perform repeat testing 8–10 weeks after travel if they had known exposure to an infectious patient or worked for a prolonged period in an area with high incidence of disease or increased prevalence of multidrug resistant TB (MDR-TB). Routine vaccination of US health care workers with bacillus Calmette-Guérin (BCG) is not recommended; by contrast, some experts do advise vaccinating health care workers who will work in settings with high TB transmission risk and a high prevalence of isoniazid-resistant and rifampin-resistant strains. Currently, however, no FDA–approved BCG formulations are available in the United States.

Personal Protective Equipment

Health care workers should consistently follow standard precautions and apply other transmission-based precautions (e.g., airborne, contact, droplet) as needed; anyone untrained in infection-control practices should not participate in patient care or in activities with risk for exposure to infectious materials. For details, guidelines, and training materials on standard precautions and personal protective equipment (PPE). PPE approved for single use only should not be reused. Health care workers should maintain strict safety standards, even if local practices are less stringent.

Aprons, gloves, gowns, surgical masks, protective eyewear, and air-purifying respirators (e.g., a National Institute for Occupational Safety and Health [NIOSH]–approved N95 filtering facepiece respirator fit-tested to the worker) might all be necessary to achieve an adequate level of personal protection. Specialized (enhanced) PPE and infection- control techniques might be indicated for infections (e.g., avian influenza, COVID-19, Ebola virus disease, MERS) that pose a high risk to health care workers. Current disease-specific epidemiology can be found on the CDC Travelers’ Health website.

Because equipment and facilities for airborne isolation are limited or unavailable in many countries (whenever possible, local resources should be determined in advance), health care workers should consider bringing a personal supply of PPE. This includes NIOSH-approved respirators with a ≥N95 level of protection (e.g., a reusable elastomeric half-mask respirator, a supply of disposable filtering facepiece respirators). Considering the available equipment, health care workers should be properly trained for all anticipated procedures (e.g., PPE donning and doffing, respirator fit testing, reusable respirator decontamination).

Health care workers should anticipate environmental conditions (e.g., high heat, humidity) that can make PPE, particularly high-level PPE (e.g., gowns, respirators), challenging to wear and use for extended periods. In addition, identifying situations where enhanced PPE is needed can be difficult, especially when working in locations where TB is highly prevalent and patient isolation is suboptimal.

Infection Transmission Routes

Airborne & Respiratory Droplet–Transmitted Infections

Although some airborne or respiratory droplet–transmitted infections (e.g., COVID-19, seasonal influenza, measles, varicella) are vaccine- preventable, others (e.g., MERS, pneumonic plague, TB) do not have routine or even available vaccines. TB infection is a particular concern for health care workers going to areas with high incidence of disease or an increased prevalence of MDR-TB (see Sec. 5, Part 1, Ch. 22, Tuberculosis).

Infections Transmitted by Blood & Body Fluids

Health care workers are at risk for infections transmitted through blood or body fluids via mucous membrane, percutaneous, or nonintact skin exposures. Bloodborne pathogens (e.g., HBV, HCV, HIV) can be transmitted through these routes. Other bodily fluid sources of infection for hepatitis viruses and HIV include amniotic fluid, cerebrospinal fluid, pericardial fluid, peritoneal fluid, pleural fluid, semen, synovial fluid, and vaginal secretions.

Other pathogens transmitted to health care workers via blood or bodily fluids include several not endemic to the United States (e.g., Brucella species, the bacteria that cause brucellosis; viruses like dengue and Ebola; and parasitic infections, such as malaria).

Percutaneous & Dermal Exposure

Typically, exposure to bloodborne pathogens occurs as a result of percutaneous exposure to contaminated sharps, including lancets, needles, scalpels, and broken glass from capillary or test tubes. Infection risk is increased after percutaneous exposures to larger blood volumes (e.g., deeper injuries, hollow-bore needles, procedures involving direct cannulation of an artery or vein, or visible blood on the injuring device).

Needlestick injuries are a common mode of percutaneous exposure to bloodborne pathogens; health care workers should avoid practices known to increase risk for needlestick injuries (e.g., recapping or using needles to transfer a bodily fluid between containers). Health care workers should be aware that safety-engineered medical devices and biosafety equipment (e.g., sharps containers) might not be available.

Skin exposures to potentially infectious bodily fluids are only considered a risk for bloodborne pathogen infection if skin integrity is compromised (e.g., through dermatitis, abrasion, open wounds). Higher circulating viral load in the source patient is also thought to increase transmission risk, which can be of particular concern in resource-poor settings where treatments for viral hepatitis and HIV are limited.

Infection Risk

Health care workers who have received hepatitis B vaccine and have developed immunity to the virus are at virtually no risk for infection. Reported risk for HCV transmission after a percutaneous exposure to HCV-infected blood or body fluid varies; recent studies report rates around 0.2%. The risk for HIV transmission is ≈0.3% after a percutaneous exposure to HIV-infected blood, and ≈0.09% after a mucous membrane exposure. Unless visibly bloody, feces, nasal secretions, saliva, sputum, sweat, tears, urine, and vomitus, are not considered infectious for HCV or HIV.

Postexposure Intervention
Immediate Actions

Health care workers with occupational exposures to blood or body fluids should thoroughly wash the exposed area with soap and water. If mucous membrane exposure has occurred, the area should be flushed with copious amounts of water or saline.

If possible, assess both HCV and HIV infection status of the source patient; rapid HIV testing of the source patient is preferred. Exposures originating from source patients who test HIV negative are considered not to pose HIV transmission risk unless they have clinical evidence of primary HIV infection or HIV-related disease (see Sec. 5, Part 2, Ch. 11, Human Immunodeficiency Virus / HIV). HBV testing of the source patient might be indicated if the health care worker is not a documented responder to hepatitis B vaccination.

Perform baseline testing of the exposed health care worker for HCV and HIV infection immediately after exposure. In addition, if the exposed health care worker has no documented serologic response to hepatitis B vaccination, perform baseline testing for HBV infection. Seek qualified medical evaluation as soon as possible to guide decisions for postexposure prophylaxis (PEP).

Postexposure Prophylaxis

A decision to initiate PEP is based on the timing, nature, and source of the exposure. Regimen choice is affected by available drugs, the exposed person’s medical history and pregnancy status, potential drug interactions, and the possibility of exposure to a drug-resistant strain. Expert consultation is important when considering PEP. When expert advice is not immediately available, contact the National Clinician Consultation Center (888-448-4911) for assistance in managing occupational exposures to HBV, HCV, and HIV.

Hepatitis B

If the source patient is not confirmed to be HBV surface antigen (HBsAg) negative, begin PEP with hepatitis B immune globulin and vaccination for health care workers who do not have documented serologic response to hepatitis B vaccination or who are incompletely vaccinated against hepatitis B.


To reduce the chance of HIV transmission after percutaneous or mucous membrane exposures to potentially infectious bodily fluids from patients with known or potential HIV infection, PEP is recommended. A number of medication combinations are available for PEP (see HIV and Occupational Exposure. Before travel, employers and health care workers should determine whether HIV PEP regimens are available at their practice locations; if not, they should consider bringing their own reliable supply for emergency use.

HIV PEP should be initiated as soon as possible after exposure. PEP efficacy is thought to decrease with increasing time after exposure, particularly if initiated >72 hours after exposure, and PEP can be stopped if new information changes the decision to treat. Counsel PEP recipients about drug interactions, drug toxicities, and the importance of adherence.

Testing & Counseling

Postexposure testing and counseling are important follow-up measures for exposed health care workers, whether hepatitis B immune globulin or HIV PEP have been administered or not (see Box 9-04 for details).

Box 9-04 Postexposure testing & counseling


Hepatitis B virus (HBV): If the health care worker is not a documented serologic responder to hepatitis B vaccination or is incompletely vaccinated, conduct baseline and follow-up testing for HBV infection for those with known or potential HBV exposure.

  • Perform a baseline test for total antibodies to HBV core antigen (HBcAg) as soon as possible after exposure.
  • Perform follow-up testing for HBV surface antigen (HBsAg) and HBcAg at 6 months after exposure.

Hepatitis C virus (HCV): Conduct baseline and follow-up testing for HCV infection for those with known or potential exposure to HCV.

  • Perform a baseline test for HCV antibody; if the baseline test is positive, perform an HCV RNA test.
  • Perform follow-up testing for HCV RNA at 3–6 weeks after exposure.
  • Test for HCV antibody at 4–6 months after exposure; if positive, perform a confirmatory RNA test.

HIV: Conduct baseline and follow-up testing for HIV infection for those with known or potential HIV exposure.

  • Follow-up testing at 6 weeks, 3 months, and 6 months.
  • Follow-up testing at 6 weeks and 4 months is acceptable if a 4th-generation, combination HIV p24 antigen-HIV antibody test is used.
  • Extended HIV follow-up testing for ≤12 months, for people infected with HCV (after exposure to a co-infected source).


Advise exposed health care workers to take precautions to avoid secondary transmission (e.g., abstain from sexual contact, use condoms or other barrier methods to prevent sexual transmission, avoid blood or tissue donations, and refrain from breastfeeding, if possible) especially during the first 12 weeks after exposure

Psychological counseling is essential because the emotional impact of occupational exposures can be substantial and can be exacerbated by stressors inherent to the overseas work environment.

The following authors contributed to the previous version of this chapter: Henry M. Wu, Alan G. Czarkowski, Eric J. Nilles

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Schillie S, Vellozzi C, Reingold A, Harris A, Haber P, Ward JW, et al. Prevention of hepatitis B virus infection in the United States: recommendations of the Advisory Committee on Immunization Practices. MMWR Recomm Rep. 2018;67(RR-1):1–31.

Sosa LE, Njie GJ, Lobato MN, Bamrah Morris S, Butchta W, Casey ML, et al. Tuberculosis screening, testing, and treatment of U.S. health care personnel: recommendations from the National Tuberculosis Controllers Association and CDC, 2019. MMWR Morb Mortal Wkly Rep. 2019;68(19):439–43. Box 9-04 Postexposure testing & counseling