During the 4-year period from 2016–2019, 4 cases of laboratory-acquired Zika virus infection were reported in the United States: 2 associated with needlestick injuries and 2 in which the means of exposure was undetermined. In laboratories where work with Zika virus is performed, good laboratory safety practices are critical to reduce the risk to personnel of Zika virus exposure and disease.

Many factors affect the likelihood of Zika virus infection following exposure, including the type and severity of any injury or exposure, route of exposure, viral concentration and dose, transmissibility of the strain, immediate management of any recognized exposure, and the worker’s health status. At least 3 other potential occupational exposures to Zika virus have occurred among researchers without subsequent Zika virus infection: a bite from an infected mouse that punctured the skin of a gloved researcher’s finger (7), a puncture wound from a needle that occurred when a double-gloved researcher was collecting a blood sample from a Zika virus-infected ferret (M. Sauri, Occupational Health Consultants, pers. comm., 2017 Jan 30), and a thumb laceration from a scalpel contaminated with chicken blood in a researcher harvesting chickens inoculated with Zika virus (7). Other exposures or infections might have occurred and remained unreported or been undetected if appropriate testing was not completed.

A limitation of this report is that viral sequencing could not be done to provide supporting evidence that the Zika virus infections were laboratory-acquired. However, the patients lived in areas without endemic Zika virus disease and patient investigations revealed no other risk factors for acquisition of Zika virus infection (i.e., no patients had traveled, had sexual contact with a traveler, or received a blood transfusion or organ transplant). Therefore, the infections were likely laboratory-acquired.

The Biosafety in Microbiological and Biomedical Laboratories guidelines recommend BSL-2 practices, safety equipment, and facilities for working with Zika virus (8). Similarly, recommendations exist for animal BSL-2 practices, equipment, and facility requirements when animal studies involving Zika virus are conducted (8). In addition, laboratories should perform a risk assessment to determine whether certain procedures or specimens might require higher levels of biocontainment (9). For example, manipulating large quantities of virus or high titer preparations might warrant a shift to BSL-3 practices, including additional respiratory protection (8). Altering practices might be particularly critical when working outside a biosafety cabinet or when not wearing adequate PPE to protect against aerosol or droplet transfer of infectious material.

Laboratory personnel should have appropriate training regarding precautions to prevent exposures associated with the tasks they perform (8). Institutional policies also should be in place and accessible. Because careful management of needles and other sharps is vital, policies should include recommendations for the safe handling of sharps; for needles, actions that involve manipulation by hand before disposal, including bending, recapping, or removing from the syringe, are not advised (8). Biosafety in Microbiological and Biomedical Laboratories guidelines provide comprehensive information on recommended practices, safety equipment, and laboratory facilities (8). Broader guidance for protecting workers from occupational exposure to Zika virus also is available from the Occupational Safety and Health Administration and from the Centers for Disease Control and Prevention National Institute for Occupational Safety and Health (10).

Appropriate evaluation and management of occupational Zika virus exposures is crucial. If an incident occurs, established workplace procedures for initial wound management or mucous membrane exposures should be followed and the event immediately reported to a supervisor. No specific Zika virus post-exposure prophylaxis exists; however, as soon as possible after the incident, a baseline serum sample should be obtained and stored in case comparison with a convalescent serum sample is needed. Persons should be advised to take steps to prevent potential sexual transmission of Zika virus and to avoid mosquito bites if in a geographic area with risk for mosquito-borne transmission of Zika virus. These measures should be continued until laboratory testing excludes infection; if Zika virus infection is confirmed, additional counseling should be provided. If symptoms consistent with Zika virus disease occur within 2 weeks of the exposure, serum and urine should be collected and tested by using appropriate molecular and serologic methods. For an exposed person who remains asymptomatic, a serum sample should be obtained >2 weeks postexposure. This serum sample should be tested for Zika virus IgM and if positive, tested by plaque-reduction neutralization test, and results compared with those from the baseline sample to assess for asymptomatic infection. Similarly, if a person is symptomatic within 2 weeks of exposure and test results on collected samples are negative, indicating the illness is unrelated to Zika virus infection, consideration should be given to obtaining an additional serum sample at >2 weeks postexposure and similarly evaluating for asymptomatic infection.

Although Zika virus transmission has declined substantially in recent years, research using Zika virus is ongoing. Exposure and infection are occupational risks for laboratory and biomedical research workers who work with live virus. Strong infection prevention practices are essential for reducing this risk (11). Establishing and implementing appropriate policies and procedures, providing adequate training, making available and ensuring proper use of PPE and other safety equipment, and confirming facilities are suitable for the type of work being conducted are all required to protect personnel from any adverse health outcomes.