Work with the 1918 flu virus was done in an enhanced BSL-3 (BSL-3+) lab, which requires the researcher to wear a battery powered air purifier and shower upon leaving the facility. These biosafety conditions are not, however, the highest level of containment. A stricter BSL-4 lab requires the user to wear a full space suit while at work. In addition to safety precautions, there are also security barriers to prevent any unauthorized individual from entering a BSL-3 or BSL-4 lab. Officials maintained that at the CDC facility where the work was done, only Dr. Tumpey had access to the virus, and in addition to having undergone an extensive background check, could only gain access to the facility with a retinal scan. Furthermore, all of the researchers involved in the project were taking antiviral drugs so that even if they should become exposed to the virus, they would not get infected and risk infecting others.
Nonetheless, debate was sparked in the scientific community about whether these containment and security precautions were good enough. Researchers from other countries suggested that they would not have been able to do the same work in anything less than BSL-4 conditions. The US NIH guidelines for agents that require BSL-3 containment include those causing serious or lethal human disease for which preventatives or therapeutics may be available. Since the 1918 strain had been shown to be susceptible to the antiviral drugs Tamiflu and Flumadine, it was not considered necessary to restrict this work to BSL-4 conditions. Regardless, many researchers and the public have continued to express safety concerns, especially after three workers in a BSL-3 lab were infected with SARS.