Answer by Tirumalai Kamala:
Sounds reasonable to think that being regularly exposed to sick people would help doctors and nurses build up a stronger immune system except we need to consider the type of sick people. To build up a stronger immune system, we need to be frequently exposed to a variety of infections, a situation that certain health-care workers share with daycare workers, kindergarten and primary school teachers, and funeral industry workers (1).
All health care workers are not equally exposed to infections, some such as endocrinologists, oncologists and radiologists being less exposed and others such as doctors-in-training (internists), emergency doctors, internal physicians (general practitioners), pediatricians and infectious disease specialists being more exposed. Does their increased exposure to infections help these types of doctors build up a stronger immune system? What does the reported data suggest? Data is sporadic, not systematic.
We cannot generalize because different countries have different risk-assessment and -alleviation measures, and different infections have different prevalence rates in different countries. For example, this 2007 study (2) states that Brazil did not have a national surveillance system for tracking occupational infections among health-care workers at the time of the study.
There were two landmark meta-analysis studies published by Kent A. Sepkowitz at the Memorial Sloan-Kettering in 1996 (3, 4). He reviewed English-language articles and abstracts published between January 1983 until February 1996 on occupationally acquired infections among health-care workers. He found ‘More than 15 airborne infections have been transmitted to health care workers, including tuberculosis, varicella, measles, influenza, and respiratory syncytial virus infection. Outbreak-associated attack rates range from 15% to 40%. Most occupational transmission is associated with violation of one or more of three basic principles of infection control: hand-washing, vaccination of health care workers, and prompt placement of infectious patients into appropriate isolation‘. His compelling summation of the data speaks for itself (see below), and suggests that rather than protected, health-care workers are more at risk for many infections, and that prophylactic vaccinations have been most effective in reducing their infection rates.
Airborne diseases: Inhalation most common reason.
Blood-borne diseases: It’s obvious why health-care workers are at increased risk, no? Needle-pricks.
Oral-Fecal diseases: Insufficient hand-washing most common cause.
Thus, health care workers are more, not less, at risk from blood-borne and airborne infections.
Blood-borne infectious diseases spread by needle prick
The WHO estimates that occupational exposure of health-care workers to blood-borne pathogens is responsible for ‘66000 cases of hepatitis B, 16000 cases of hepatitis C, and 200–5000 cases of human immunodeficiency virus (HIV) annually, as well as a smaller number of other infections such as tuberculosis or malaria‘ (5).
Hepatitis B and C are typical needle-prick and blood-borne diseases. Studies suggest health care professionals have a four-fold higher risk of acquiring Hepatitis B, HBV (6). Among specializations, dentists, dialysis technicians, laboratory cleaning service employees, nurses and physicians have the highest HBV rates (7, 8). In the US, before mandatory vaccination policies, HBV infection rates were 3 to 10 times higher among dentists (9, 10, 11, 12, 13, 14) with 16 to 23% prevalence rates overall for health care workers (15, 16, 17). Since the 1980s, US HBV prevalence rates among health care workers have declined to about 9% following better HBV vaccination coverage (18, 19).
Studies from Nigeria and South Africa show that tuberculosis is a high risk for health-care workers (20, 21).
Chicken pox; Varicella zoster virus (VZV)
Causes herpes zoster, a painful skin rash, has both acute and chronic phases as well as nerve pain (neuralgia). Spread by aerosol droplets from coughs or sneezes, also from the patients’ infected blisters and fomites (any inanimate object touched by the patient). Earlier, questionnaire-based studies suggested that health-care workers are more immune to VZV (22, 23). However, these studies had 3 key flaws: Low response rates, self-reporting, small sample sizes. The first population-based study comparing VZV incidence between health-care workers and the general population in Taiwan ‘did not find any protective effect against herpes zoster among health-care workers. In our study, the health-care workers had a higher incidence of herpes zoster than the general adults for the 20-49 year age groups. After controlling for sex, age and other factors, health-care workers had a higher odds chance of getting herpes zoster than the general adults’ ‘Health-care workers, who work long hours in hospitals, have a greater chance of exposure to VZV compared to general adults. Transmission of VZV poses a major infection risk for health-care workers in the hospital environment’ (24).
- Davidson, Susan Salter, and William H. Benjamin. “Risk of infection and tracking of work-related infectious diseases in the funeral industry.” American journal of infection control 34.10 (2006): 655-660
- Sepkowitz, Kent A. “Occupationally acquired infections in health care workers: Part I.” Annals of internal medicine 125.10 (1996): 826-834.
- Sepkowitz, Kent A. “Occupationally acquired infections in health care workers: part II.” Annals of internal medicine 125.11 (1996): 917-928.
- Prüss-Üstün A, Rapiti E, Hutin Y. Sharps injuries: Global burden of disease from sharps injuries to health-care workers. WHO Environmental Burden of Disease Series, No 3. World Health Organization, Geneva, Switzerland. 2003.
- E. Dannetun, A. Tegnell, A. Torner, and J. Giesecke, “Coverage of hepatitis B vaccination in Swedish healthcare workers,” Journal of Hospital Infection, vol. 63, no. 2, pp. 201–204, 2006.
- EPINET, “Needle stick prevention devices,” Health Devices, vol. 28, pp. 381–407, 1999.
- Jha, Arun Kumar, et al. “Hepatitis B infection in microbiology laboratory workers: prevalence, vaccination, and immunity status.” Hepatitis research and treatment 2012 (2012).
- Mosley JW, White E. Viral hepatitis as an occupational hazard of dentists. J Am Dent Assoc 1975;90:992–7.
- Mosley JW, Edwards VM, Casey G, et al. Hepatitis B virus infection in dentists. N Engl J Med 1975;293(15):729–34.
- Feldman RE, Schiff ER. Hepatitis in dental professionals. JAMA 1975;232:1228–30.
- Smith JL, Maynard JE, Berquist KR, et al. From the Centers for Disease Control: comparative risk of hepatitis B among physicians and dentists. J Infect Dis 1976; 133(6):705–6.
- Hollinger FB, Grander JW, Nickel FR, et al. Hepatitis B prevalence within a dental student population. J Am Dent Assoc 1977;94:521–7.
- Wei RB, Lyman DO, Jackson RJ, et al. A hepatitis serosurvey of New York dentists. NY State Dent J 1977;43:587–90.
- Schiff ER, Medina MD, Kline SN, et al. Veterans administration cooperative study of hepatitis and dentistry. J Am Dent Assoc 1986;113(3):390–6.
- Gerberding JL. Incidence and prevalence of human immunodeficiency virus, hepatitis B, hepatitis C and cytomegalovirus among healthcare personnel at risk for blood exposure. Final report from a longitudinal study. J Infect Dis 1994;170(6):1410–7.
- Rose, Gregory, and Virginia R. Roth. “Infections in healthcare workers.” Evidence-Based Infectious Diseases (2009): 291
- Cleveland JL, Siew C, Lockwood SA, et al. Hepatitis B vaccination and infection among US dentists, 1983–1992. J Am Dent Assoc 1996;127: 1385–90.
- Mahoney FJ, Stewart K, Hu H, Coleman P, Alter MJ. Progress toward the elimination of hepatitis B virus transmission among health care workers in the United States. Arch Intern Med 1997;157:2601-5)
- Malangu, Ntambwe, and Adelaide Legothoane. “Analysis of occupational infections among health care workers in Limpopo Province of South Africa.” Global journal of health science 5.1 (2012): p44 )
- Salami, A. K., and P. O. Oluboyo. “Health careworkers and risk of hospital-related tuberculosis.” Nigerian journal of clinical practice 11.1 (2008): 32-36
- Solomon BA, Kaporis AG, Glass AT, Simon SI, Baldwin HE. Lasting immunity to varicella in doctors study (L.I.V.I.D. study). J Am Acad Dermatol 1998; 38: 763.
- Terada K, Hiraga Y, Kawano S, Kataoka N. Incidence of herpes zoster in pediatricians and history of reexposure to varicella-zoster virus in patients with herpes zoster. Kansen Zasshi 1995; 69: 908–912.
- WU, Chen‐Yi, et al. “Do the health‐care workers gain protection against herpes zoster infection? A 6‐year population‐based study in Taiwan.” The Journal of dermatology 37.5 (2010): 463-470.