Introduction
The occupational exposure limit (OEL) is a value that characterizes the maximum amount of a substance that a subject can be exposed to without harm. It is the main value of the environmental standardization of the content of toxic substances in the natural environment. The OEL is usually understood as a concentration of a chemical compound or a biological agent, which, with daily exposure to the human body for a long time, will not cause any pathological changes. Moreover, it also should not violate the biological optimum for humans. When establishing the OEL of biological agents in the air basin of populated areas or the air of the working area, the limitations are guided by the potential harmfulness. It is important to understand the OEL for COVID-19, as the coronavirus has in a short period conquered the whole planet.
Occupational Exposure Limit of COVID-19
The infectious dose of the pathogen is the minimum number of microbial cells or virus particles that can cause an infectious process. The size of the infectious dose depends on the virulent properties of the pathogen: the higher the virulence, the lower the infectious dose. The infectious dose for the development of COVID-19 disease is 100-700 particles of the SARS-CoV-2 coronavirus. It represents the minimum amount of viral particles that will infect a person if they get on their mucous membranes. To meet with one infectious dose of coronavirus is a very good option: there are huge chances of a mild or even asymptomatic form of the disease. To meet ten infectious doses at once poses a significant risk to one’s life.
Comparison and Contrast with Other Viruses and Bacteria
The infectious dose is different for different biological agents. For hepatitis B, it is about 100 viral particles, and for the human immunodeficiency virus – about 10,000. Thus, it is clear that the virulence of coronavirus, in contrast with other viruses, is quite high. In the case of COVID-19, such a small infectious dose is enough for people to get sick because until now humanity has never encountered a new type of coronavirus. Meyers et al. (2020) state that “unlike its predecessors, SARS-CoV-2 spread rapidly across the world, reaching pandemic levels within 2 months” (p. 1605).
However, the situation is a little different with bacteria. The size of the infectious dose of a bacteria depends not only on its virulence but also on the individual sensitivity to this bacteria, as well as the conditions of the infection process. For example, to be infected with cholera, a person with normal stomach acid must swallow at least one hundred million bacterial cells. At the same time, to get infected with the plague, just several, or, theoretically, even a single cell of the plague bacillus is enough. Moreover, it is known that various types of the same bacteria genus have different infectious doses. According to Baker and The (2018), “ingestion of Shigella, which typically has a low infectious dose, commonly results in an aggressive watery or mucoid/bloody diarrhea” (p. 450). Virulent strains of Shigella dysenteriae cause disease in adults at a dose of 10 microbial bodies, while the minimum infectious dose of Shigella flexneri subsovar 2a is 102 microbial bodies. Finally, the virulence of Shigella sonnei is even lower – the minimum infectious dose is 107 microbial bodies.
Conclusion
COVID-19 has proven to be a highly infectious disease, and it requires a lot of further studies. It is clear, however, that the maximum dose of the virus is received by people through direct contact with a patient with COVID-19. That is why doctors in hospitals are the most susceptible to infection and are the least protected from it. Especially it is true for doctors who have to interact directly with the patients – this is where the maximal threat arises. This particular danger of their work must be minimized to successfully battle the virus.
References
Baker, S., & The, H. C. (2018). Recent insights into Shigella. Current Opinion in Infectious Diseases, 31(5), 449–454.
Meyers, C., Robison, R., Milici, J., Alam, S., Quillen, D., Goldenberg, D., & Kass, R. (2020). Lowering the transmission and spread of human coronavirus. Journal of Medical Virology, 93(3), 1605–1612.