Suspicions abound that the SARS-CoV2 virus that caused the COVID-19 outbreak may have escaped from a containment laboratory in Wuhan, China, despite scientific experts weighing in that the disease more likely originated in bats. These concerns have been amplified by reports that the State Department knew about safety lapses in the lab. Even with strict safety precautions, there are several ways a virus could escape from a lab.
The Centers for Disease Control and Prevention (CDC) issues guidance on safe microbiology laboratory practices, in addition to conducting inspections of laboratories that handle high threat agents that cause diseases [MK1] like Ebola, anthrax, and plague. Laboratories operate along a continuum, from Biosafety Level 1 (BSL-1) through BSL-4, depending on what they work on and what controls they must follow. BSL-3 and 4 labs operate with the highest safety precautions because they work with agents known to infect laboratorians, especially from airborne contact. Therefore, they require specialized “containment.”
BSL-3 and 4 containment laboratories utilize safety features developed over decades to minimize the chances that a pathogen will escape. These include engineering controls, such as negative pressure air handling and filtered exhaust air; waste decontamination processes, such as autoclaving, steam sterilization, or incineration; specialized equipment, such as biological safety cabinets (hoods). Entry is restricted to workers who have undergone rigorous background vetting, health and safety checks, and repeated training.
Despite all the precautions, laboratory accidents do occasionally occur. Pathogens don’t just fly out on their own, typically humans help them along through inadvertent errors. U.S. laboratories have procedures for handling those errors internally to minimize the chances for breaches of containment. Even then, there are four basic ways a pathogen could escape the confines of a lab and potentially cause an outbreak.
This method is highly unlikely. Containment laboratories have sophisticated air handling systems, which include high-efficiency particulate air (HEPA) filtration before laboratory air is released into the environment, sometimes passing through two HEPA filters in series. In the unlikely event that a pathogen gets around these filters, many pathogens don’t survive well out in the world - especially in sunlight. Lab scientists typically work with small volumes of organisms. If a pathogen were to escape, it would disperse into the atmosphere at extremely low concentrations, which would likely be too low to cause infections.
One notable exception occurred in 1979 in the town of Sverdlovsk in the former Soviet Union. At least 66 people died from inhalational anthrax, a highly deadly disease, after anthrax spores escaped from a lab after a technician forgot to replace a filter. The lab in question was a bioweapon facility called Compound 19, and they were working with unusually large volumes of spores. Anthrax spores are also particularly hardy in the environment, leading to a much higher chance for survival long enough to infect people.
The Soviets went to great lengths to cover up the event (much like the Chernobyl disaster), even sending scientists to the U.S. to present data to prove that the disease originated from tainted meat that caused gastrointestinal anthrax. After the breakup of the Soviet Union, U.S. scientists were allowed to investigate. They determined, from autopsy records, visits to graveyards, interviews with victims’ families and pathologists, and analysis of where the infections occurred, that it was likely due to airborne release from the bioweapon facility. Boris Yeltsin eventually acknowledged it was due to military activity.
The redundant safety measures that are used in containment laboratories are there for a reason: people make errors and systems fail. Before a new driver gets a license, they go through a series of steps – a permit exam, driving under the supervision of a licensed driver, and finally, passing a driver’s test. Even then, every time they drive, before they turn the ignition on, they do a number of preparations, such as positioning the rearview and side mirrors and adjusting the seat. Similarly, before anyone works independently in the lab, they undergo a period of observation with an experienced colleague. Then, each time they enter the lab, they follow a series of practiced procedures.
Despite significant precautions, regular training, and highly skilled workers, two errors can occur: someone accidentally ships the wrong pathogen outside the lab, as occurred when the CDC shipped H5:N1 flu samples out in 2014, or a lab worker can occasionally catch their own experiment. Notably, in 2004, Antonina Presnyakova, a highly experienced lab scientist in Russia died from Ebola virus disease after she stuck herself with a contaminated needle.
Even if someone were infected in the lab, one of the key factors that limits spread outside the lab is that many of the pathogens in containment laboratories are infectious only to a single individual. They are not contagious from one person to another. Of course, if the SARS-CoV2 virus actually got out of the lab this way, it would be one of the exceptions.
Animals are used routinely in containment labs to test vaccines and treatments. If an animal was infected and was stolen from a lab, theoretically it could act as a virus transporter akin to a “mule” smuggling drugs across the border. However, containment laboratories have incredibly high security that makes this situation highly improbable.
But pathogens are sneaky. They use our mistakes as opportunities to spread. Laboratory workers in hospitals and research labs wear lab coats for a reason, and they remove them when they leave the lab. In containment laboratories, requirements are even more stringent. Workers strip naked and don scrubs before they enter the lab, and they remove their scrubs and shower upon exit. This is a simple way to prevent pathogens that may have contaminated their clothes or hair inside the lab from hitching a ride out of the lab. Similarly, fomites, such as lab equipment or instruments also serve as potential vehicles for spread, but strict decontamination protocols prevent pathogens from escaping on them.
This is often one of the greatest concerns (particularly because it makes a great storyline for a movie). Containment labs now have video monitoring for both security and safety, but there is a history of individuals purposefully releasing pathogens. One still up for debate is whether the 2001 anthrax attacks were smuggled out of a lab. There are other confirmed examples: Dianne Thompson, who worked in a microbiology laboratory in Texas, infected 12 of her coworkers using Shigella-contaminated donuts and pastries, giving them severe diarrhea. The Rajneeshee cult in the Dalles, Oregon had their own lab and sought to improve their standing in county elections by contaminating local salad bars with Salmonella. Despite causing at least 751 people to come down with severe diarrhea, they still were not successful in the elections. The cult eventually disbanded and some members were jailed.
Although it is far more likely that the SARS-CoV2 virus came from nature rather than a lab in Wuhan, China, it is very difficult to prove a negative. Similar to what was done with the anthrax Sverdlovsk incident in the former Soviet Union, an international scientific team needs to be allowed to conduct a full investigation to determine what really happened. Until then, the suspicions and rumors that it came from a lab will continue to spread as efficiently as the virus itself.