7. 1928: Discovery of penicillin by Alexander
Fleming
• Scottish physician and scientist
• Discovered antibacterial properties of Penicillium notatum mold
• Isolated and purified by Florey & Chain
• Major step forward in infection control
Figure 6: Petri dish showing bacterial inhibition by penicillium mold, 2004. Cummings, B.
Retrieved from http://www.pharmamicroresources.com/2015/01/new-penicillin-mechanism-
revealed.html/ 7/17/15.
8. 1948: Framingham Heart
Study
• Joint venture between Boston
University and NHLBI
• Longitudinal study intended to
discover modifiable characteristics of
individuals with CVD
• Has followed 3 generations of
participants
• Identified major risk factors for CVD
Figure 7: Graphic showing 3-generation cohorts for FHS, n.d.
Retrieved from http://sphweb.bumc.bu.edu/otlt/mph-
modules/ep/ep713_history/EP713_History5.html/ 7/17/15.
9. 1951: Establishment of Epidemic
Intelligence Service at CDC by Alexander
Langmuir
• Father of infectious disease epidemiology
• CDC’s first Chief Epidemiologist (1949-70)
• Created disease surveillance
• EIS established in response to bioterrorism threat
• Contributed to eradication of polio in US
http://www.cdc.gov/socialmedia/tools/buttons/trainingandeducation/index.html/
10. 1951: British Doctors Study
Links Smoking to Lung Cancer
• Results: higher death rate from lung
cancer in smokers
• Results also suggested higher death rate
from coronary thrombosis
• Further follow-up showed increase in
smoker vs. non-smoker death rate ratios
Figure 9: Graph combining results of Doll & Hill (1954) and
Doll & Peto (2004) studies, 2009. Heron, J.F. Retrieved from
http://www.oncoprof.net/Generale2000/g02_Prevention/Index
/Index_gb-pr09.html/ 7/17/15
11. 1980: Worldwide Eradication of Smallpox
• Smallpox Eradication Programme created by WHO
• Development of bifurcated needle
• 2 main strategies: surveillance and containment
• Last naturally occurring case in Somalia, 1977
• Eradication declared a success in 1980
Figure 10: Components of smallpox vaccine kit, 2002. Gathany, J.
Retrieved from http://phil.cdc.gov/phil/details.asp/ 7/18/15.
12. 1981: Start of the AIDS
Pandemic
• Opportunistic infections in otherwise
healthy people
• Initially thought to be an gay-related
illness
• Discrimination and stigma hampered
research efforts
• 39 million deaths worldwide since
onset
• Proven preventative strategies
Figure 11: Map showing distribution of HIV-positive
Individuals worldwide, 2013. World Health Organization.
Retrieved from http://www.who.int/topics/hiv_aids/en/ 7/18/15.
13. 2006: Licensing of
Gardasil (HPV Vaccine)
• 14 million new HPV infections
annually worldwide
• Causal link between HPV and
cervical cancer found in 1990’s
• 500,000 cervical cancer diagnoses
annually worldwide
• Half of those die from disease
• Vaccine raised controversy
because HPV is an STI
Figure 12: Vial of HPV vaccine, 2007. Christian, J. Retrieved
from https://en.wikipedia.org/wiki/Gardasil/ 7/20/15.
14. 2015: Measles Outbreaks
• 5 outbreaks and 178 cases since Jan
2015
• Likely spread by an infected overseas
traveler
• Many parents refuse MMR vaccine
over autism fears
• Herd immunity decreased
• Original study linking MMR and
autism debunked
Figure 13: Percentages of unvaccinated US residents infected
with measles, by reason for not getting vaccinated, 2014.
Centers for Disease Control. Retrieved from
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6322a4.ht
m?s_cid=mm6322a4_w/ 7/20/15.
20. Clinical Perspectives on Disease
• Focused on individual
• Symptoms
• Individual risk behaviors
• Duration of illness
• Treatment/cure
Figure 19: Images of Giardia parasite, n.d. Centers for Disease Control.
Retrieved from http://www.cdc.gov/parasites/giardia/ 7/21/15.
Example: Giardiasis
Clinical presentation includes:
1. Abdominal pain and bloating
2. Dehydration
3. Watery diarrhea
4. Fatigue
5. Nausea and vomiting
Management:
1. Antiparasitic drugs (Flagyl)
2. Supportive care
21. Epidemiological Perspectives on
Disease
• Focused on community
• Source of disease
• How many afflicted
• Potential for spread
Example: Giardiasis
• 176 cases between Jun 2005 and May
2009
• Crude incidence rate: 8.8 per 100,000
• 3 main risk factors:
1. Traveling within Canada (52%)
2. Contact with household pets (43%)
3. Swimming (44%)
Figure 20: Life cycle of Giardia lamblia, n.d. Shangdong University.
Retrieved from
http://www.pathobio.sdu.edu.cn/sdjsc/parasiteimages/giardia_lifecycle.h
tml/ 7/21/15/
Hello, my name is Julia Weston. This PowerPoint presentation is intended to give a brief overview and introduction to the field of epidemiology.
Epidemiology has been referred to as one of the basic sciences of public health (CDC, 2012.) It examines the occurrence, distribution, and determinants of conditions that cause disease and death in human populations (Friis & Sellers, 2014). It is an interdisciplinary field that utilizes knowledge from other disciplines, such as biostatistics, microbiology, virology, toxicology, clinical medicine, pathology, and the social sciences (Friis & Sellers, 2014) in order to prevent and control the spread of disease. This includes infectious diseases such as tuberculosis or influenza, chronic diseases such as cancer or arthritis, and other health-related events such as smoking, vaccinations, and seat belt use (CDC, 2012.) Epidemiological research lays the groundwork for public health programs and policies. In many ways, being an epidemiologist is like being a detective. You perform an investigation based on the data you gather and draw conclusions from it.
Before we move on, let's go over some vocabulary. Determinants are factors that influence one's state of health. They can be health behaviors (poor diet, drug use), agents that promote a state of poor health (carcinogenic substances, toxins, or disease-causing microbes), genetic makeup, or demographic characteristics. These factors can either increase or decrease one's risk for developing a given disease (Friis & Sellers, 2014.) The interplay between 3 major determinants: agent, host, and environment can be seen in what is commonly called the Epidemiological Triad. Distribution involves examining both the frequency and patterns of a disease (CDC, 2012.) Frequency refers to the number of occurrences of a given disease within a population. It also refers to the disease rate as compared to the size of the population. This allows epidemiologists to compare disease rates across different populations (Friis & Sellers, 2014.) A pattern of disease relates its occurrence to time, place, and/or person. Some diseases occur seasonally (time), in specific geographic areas (place), and in people with specific demographic characteristics that render them more susceptible to the disease (person) (CDC, 2015.) One of the distinguishing features of epidemiology is its concern regarding the health of populations, as opposed to the individual (Friis & Sellers, 2014.) A health-related event is anything that either positively or negatively impacts health outcomes. This includes infectious disease, mental health, and injuries (Friis & Sellers, 2014.) Finally, morbidity indicates illness, and mortality indicates death (Friis & Sellers, 2014.)
To many people, epidemiology is synonymous with outbreaks of infectious disease, with doctors and scientists wearing space-like suits, lots of dramatic photos, and people dying of horrible illnesses. However, that's only part of the picture. Outbreak investigation is one of the 6 core functions of epidemiology (CDC, 2012), along with surveillance, analytic studies, program evaluation, linkages, and development of health policies. Surveillance activities include the gathering, analysis, and dissemination of health data, which allows researchers to identify trends and patterns of disease (CDC, 2012.) If a cluster of cases of a disease are found via surveillance, field investigation can be vital to determining the source of an outbreak and to ensure that all cases are appropriately treated. It also allows for long-term follow-up (CDC, 2012.) Analytic studies are performed to test hypotheses generated through field investigations. The results are used to create public health programs and interventions (CDC, 2012.) Once these programs have been implemented, they must be evaluated for efficacy and effectiveness (CDC, 2012.) Since none of this can happen in a vacuum, it is important for epidemiologists to create and maintain relationships with other scientific disciplines, agencies, and institutions (both governmental and private.) (CDC, 2012.) Finally, all of the previous functions combine to allow epidemiologists to make appropriate recommendations when crafting health policies. (CDC, 2012.)
The history of epidemiology dates back to Ancient Greece -- Hippocrates was the first to speculate that diseases were linked with one's environment (Friis & Sellers, 2014.) This represented a movement towards more scientific methods. John Graunt was the first to collect and publish vital statistics such as birth and death rates, and was a pioneer in the use of biostatistics in the public health field (Friis & Sellers, 2014.) Edward Jenner is known as the father of vaccination, due to his discovery that inoculation with the cowpox virus (vaccinia) conferred immunity to smallpox (Friis & Sellers, 2012.) William Farr developed a sophisticated method for classifying medical conditions. This paved the way for the creation of the International Classification of Diseases (ICD) system that is in use today (Friis & Sellers, 2014.) Ignaz Semmelweis is known as the father of infection control. As an obstetric physician, he saw that women who were delivered by physicians and medical students were significantly more likely to die from puerperal sepsis (childbed fever) than those who were delivered by midwives (Best & Neuhauser, 2004.) His investigation found that the physicians and medical students would go from autopsies to deliveries with no stops in between, and he believed that there was something within the cadavers that made the women sick (Best & Neuhauser, 2004.) When he instituted a hand washing program, the mortality rate fell from 13-18% to 2%, which was comparable to the rate of the midwives (Friis & Sellers, 2014.) Many consider John Snow to be the father of epidemiology. During a cholera epidemic in London in 1854, he hypothesized that contaminated water was the source of the epidemic, flying in the face of the 'miasma' theory that was prevalent at the time (UCLA, 2005.) Using a map, he tracked all the cases of cholera, eventually leading him to remove the handle of the Broad Street water pump, which broke the chain of infection (London School of Hygiene & Tropical Medicine, 2015.) Finally, Robert Koch's research on anthrax and tuberculosis led to his discovery that diseases were caused by specific microbes. This solidified the case for the germ theory of disease, which is still relevant today (Nobel Lectures, 1967.)
Now, let's look at more recent history. The 1918 Spanish Flu pandemic killed approximately 50-100 million people worldwide between 1918 and 1919. It is estimated that 1/3 of the global population developed clinical illness (Taubenberger & Morens, 2006.) It was an unusual virus in many aspects. One was that its case-fatality rate was nearly 2.5%. In contrast, most other strains of influenza have a case-fatality rate of 0.1% or less (Friis & Sellers, 2014.) While most influenza strains kill the very young and the very old, this H1N1 strain killed normally healthy people, ranging in age from 20 to 40 (Friis & Sellers, 2014.) Research has suggested that the 1918 flu was derived from an avian (bird) flu, and since it had not been present in the human population, our bodies were naive to it, making the infection more severe (Taubenberger & Morens, 2006.) In the years after the pandemic died down, increasing advances in science and technology led to the development and marketing of the influenza vaccine, along with vaccines for polio, yellow fever, diphtheria, and other infectious diseases (Immunization Action Coalition, 2013.) In 2009, the H1N1 strain reemerged, causing another pandemic, killing between 151,700 and 575,400 people worldwide (CDC, 2012.) The 1918 epidemic is an important part of the history and evolution of epidemiology.
As a bacteriologist in the Royal Army Medical Corps during World War 1, Alexander Fleming saw that the antiseptics used to treat combat wounds, such as carbolic acid, were only effective at treating superficial wounds (FamousScientists.org, 2015.) He also demonstrated that these antiseptics damaged leukocytes, thus delyaing the body's healing process (Chemical Heritage Foundation, 2015.) After the war, Fleming continued his studies on antisepsis, and while he left for a month-long holiday in 1928, a petri dish inoclulated with Staphylococcus aureus bacteria had accidentally been left out on a lab bench, instead of being placed in an incubator as intended (Chemical Heritage Foundation, 2015.) When he returned,he found that the petri dish had been contaminated with penicillium mold, and that there were no bacterial colonies present in the area around the mold (Chemical Heritage Foundation, 2015.) Further testing showed that only penicillium molds were effective at killing bacteria, and that is was effective against other bacteria, including those responsible for scarlet fever pneumonia, and diphtheria (Famous Scientists.org, 2015.) Despite his efforts, Fleming was unable to isolate penicillin and produce it for medical use. In the 1940s, a research team led by Howard Florey and Ernst Boris Chain picked up where Fleming had left off and finally were able to purify and isolate penicillin, which led to its commercial manufacturing and widespread use, particularly during World War 2 (FamousScientists.org, 2015.) The discovery and manufacture of this effective antibiotic was a major victory in the fight against infectious diseases, for which the 3 scientists shared the 1945 Nobel Prize in Physiology/Medicine. However, Fleming himself warned against antibiotic overuse in his acceptance speech, a warning that was not heeded, as evidenced by the evolution of multi-drug resistant bacteria (FamousScientists.org, 2015.)
The Framingham Heart Study, which began in 1948, is a longitudinal cohort study whose purpose was to identify the risk factors and characteristics associated with cardiovascular disease (Framingham Heart Study, 2015.) At the time of its inception, very little was known about the determinants of CVD, and the available statistics indicated that it was a problem of epidemic proportions (Framingham Heart Study, 2015.) A cohort of 5,209 men and women between the ages of 28 and 62 were recruited from Framingham, MA. Each individual was subjected to an extensive interview and physicam examination. The researchers analyzed this data in the context of the development of CVD, looking for common patterns (Framingham Heart Study, 2015.) The subjects have returned every 2 years for additional testing, and since the beginning of the study, individuals from their 2 subsequent generations have been recruited for the study (Framingham Heart Study, 2015.) As a result of this study, many risk factors for CVD have been identified, including hypertension, dyslipidemia, smoking, obesity, diabetes, and being physically inactive (Framingham Heart Study, 2015.) The FHS was, and is, a pioneering examination into the determinants of CVD, and is an excellent example of using analytic research to improve primary preventative care.
Alexander Langmuir joined the CDC in 1949 as its Chief of Epidemiology (Thacker, 2006.) The science and practice of epidemiology changed tremendously during his tenure. He defined disease surveillance, which is one of the core functions of epidemiology (as noted earlier in this presentation) and saw its global implementation (Thacker, 2006.) He also brought the Morbidity and Mortality World Report (MMWR) to the CDC as a method of disseminating surveillance data (Thacker, 2006.) However, his greatest achievement was the creation of the Epidemic Intelligence Service (EIS), which is a 2-year post-graduate fellowship in applied field epidemiology (CDC, 2015.) It was initially formed in response to the threat of bioterrorism during the Cold War (Thacker, 2006.) The idea was to have a highly trained corps of public health professionals available to respond to any and all threats to public health (Thacker, 2006.) When the polio vaccination program was in its infancy, EIS officers were dispatched when several children contracted paralytic polio after receiving the vaccine. Their investigation found that 2 lots of the vaccine from a single manufacturer were to blame, and after clearing the other 4 manufacturers, restared the vaccination program (Thacker, 2006.) The EIS exemplifies the core functions of epidemiology and is an invaluable resource in public health practice.
In 1951, British researchers Richard Doll and and A. Bradford Hill hypothesized that the sharp increase in male lung cancer rates was due to increased cigarette consumption (Doll et al., 2004.) They sent out questionnaires to 59,600 physicians in the UK; of these, 40,564 were returned and properly completed. A cohort of 34,439 males over the age of 35 was used in the preliminary study (Doll & Hill, 1954.) The cohort was split up by smoking behaviors -- nonsmoking, 1-14 cigarettes/day, 15-24 cigarettes/day, and more than 24 cigarettes/day (Doll & Hill, 1954.) Between the start of the study in November of 1951 and March of 1954, 789 of the subjects had died, and 36 of these were due to confirmed lung cancer (Doll & Hill, 1954.) Statistical analysis showed a rise in the death rate from lung cancer from 0 per 1000 in nonsmokers to 1.14 per 1000 in the group that smoked the most (Doll & Hill, 1954.) While not as statistically significant, there was also a rise in the death rate from coronary thrombosis (3.89 per 1000 in nonsmokers vs. 5.15 per 1000 in the heaviest smokers), which suggested that smoking may be a cause of heart disease as well (Doll & Hill, 1954.) These preliminary results implicated cigarettes as the cause of the increase in male lung cancer rates (Doll & Hill, 1954.) The subjects were followed regularly, with the final questionnaire being sent out in 2001 (Doll et al., 2004.) Further research indicated that while the death rate for nonsmokers had decreased, due to advances in medical care, the death rate for smokers increased, most likely because people were starting to smoke at a younger age and smoked more (Doll et al., 2004.) However, it was also noted that quitting smoking drastically reduced mortality rates (Doll et al., 2004.) This research definitively linked cigarette smoking with increased rates of lung cancer and heart disease, and, along with other studies, kickstarted the anti-smoking movement in the United States (Mendes, 2014.)
The eradication of smallpox remains one of the greatest triumphs of epidemiology. Smallpox, otherwise known as variola, remained endemic in many areas of the world until the middle of the 20th century (Center for Global Development, n.d.) In 1959, the 12th World Health Assembly officially endorsed the goal of eradicating smallpox (History of Vaccines, 2015.) However, early efforts were stymied by lack of consistent funding and a shortage of the vaccine (Center for Global Development, n.d.) The development of the bifurcated needle by Dr. Benjamin Rubin allowed for easier administration of the vaccine, and required less of the actual vaccine than traditional vaccination methods (History of Vaccines, 2015.) In 1967, the World Health Organization created the Smallpox Eradication Programme, which relied on 2 main strategies to contain the virus: surveillance and containment (CDC, n.d.) Surveillance was used to identify individuals infected with smallpox, and the vaccine was administered to their close contacts and those people’s contacts, creating a ring of immunity around the infected person. This way, the virus had no one to infect, and the chain of infection was broken (CDC, n.d.) The last endemic case of smallpox was in a man in Somalia in 1977 (CDC, n.d.) After 2 more years of monitoring and surveillance, the WHO declared the smallpox virus eradicated in 1980 (Center for Global Development, n.d.) UNICEF (1996) estimated that 5 million lives are saved each year as a result of the eradication.
In June of 1981, an issue of the MMWR described several cases of Pneumocystis carinii pneumonia, a rare and opportunistic infection, in otherwise healthy gay men in San Fransisco (AIDS.gov, n.d.) There were also reports of a rare cancer, Kaposi’s sarcoma, in gay men in California and New York (AIDS.gov, n.d.) By the end of the year, 121 people had died from complications of severe immune deficiency (AIDS.gov, n.d.) This was only the beginning of one of the worst pandemics in recorded history. Initially, it was assumed that this was a syndrome that only affected gays, and it was dubbed GRID – gay-related immune deficiency – in 1982 (Avert.org, 2014.) The US government was very slow to respond to the growing epidemic; many medical professionals were reluctant to investigate the cause of AIDS due to widespread homophobia, and there was significant stigma and discrimination associated with the disease (Avert.org, 2014.) It became evident that HIV was transmitted via blood and sexual contact, as intravenous drug users, hemophiliacs, women, and newborn babies (via vertical transmission) joined the ranks of the afflicted (Avert.org, 2014.) Françoise Barré-Sinoussi and Robert Gallo eventually discovered that HIV was a retrovirus, and once a reliable screening test (ELISA, with confirmation by Western Blot) was developed, HIV surveillance began (UCSF, 2003.) As of 2015, it is estimated that 1.2 million people in the US are infected with HIV, and 39 million people worldwide have died from AIDS (CDC, 2015.) Many strategies have been proven to be effective at preventing the spread of HIV – correct and consistent condom use, not sharing needles if an IV drug user, screening of donated blood, the use of HAART (highly active antiretroviral therapy) in HIV-positive mothers, to prevent vertical transmission, and STI treatment (CDC, 2013.) As of now, researchers have been unable to manufacture an HIV vaccine, leaving most of the burden on preventative care.
Human Papillomavirus (HPV) is a sexually transmitted infection that typically causes genital warts (National Cancer Institute, 2015.) Nearly 14 million people will contract HPV every year (National Cancer Institute, 2015.) In the 1990s, researchers proved that almost all cases of cervical cancer are caused by HPV, with types 16 and 18 being responsible for 70% alone (National Cancer Institute, 2015.) HPV has also been implicated in vaginal, vulvar, and penile cancer (CDC, 2015.) Gardasil was developed with the intent of reducing the incidence of these types of cancers, along with preventing genital warts (CDC, 2015.) Currently, the CDC (2015) recommends that both boys and girls receive the vaccine before they age of 26. This vaccine has raised significant controversy, particularly among parents, who feel that there is no reason to vaccinate children who are not sexually active against a sexually transmitted infection (Knox, 2011.) While Gardasil is a very effective method of preventing HPV, it does not replace the need for correct, consistent condom use and regular pap smears (National Cancer Institute, 2015.) Still, this is a major milestone in the field of epidemiology: not only can we reduce the incidence of HPV infection, but we can reduce the rates of genital cancers in both men and women.
Vaccines have been one of the greatest contributions to public health. Diseases like diphtheria, pertussis, and polio are almost never seen in the United States anymore. However, the incidence rate of measles has risen significantly over the last 20 years (CDC, 2015), and this is largely due to parents refusing to have their children vaccinated (Saad et al., 2009.) Most of the refusals have been on religious, personal, or philosophical grounds, or because of fears of deleterious effects (CDC, 2015.) A 1998 study in The Lancet by Dr. Andrew Wakefield, which has since been debunked and discredited, claimed to find a link between the MMR vaccine and autism (American Academy of Pediatrics, 2014.) This purported association was the picked up by American celebrities Jenny McCarthy, who claimed that the MMR vaccine caused her son to develop an autism spectrum disorder (PBS.org, 2015.) Multiple studies have since confirmed that there is no link between the MMR and autism (American Academy of Pediatrics, 2014), but the damage had been done. As vaccination rates drop, herd immunity decreases. In 2015, there was a multi-state measles outbreak that centered around Disneyland in California. It is suspected that an overseas traveler was infected with the virus and infected many people at the theme park (CDC, 2015.) This demonstrates the importance of vaccines, along with the ramifications of not vaccinating. There are very good reasons that we don’t see diphtheria and other infectious diseases today. They haven’t magically gone away, we are just immune to them. A return to the pre-vaccine era is not a pleasant scenario to contemplate, and epidemiologists and other public health professionals will work to ensure that it doesn’t happen.
The methods and tools of epidemiology can be applied to many other scientific disciplines that are of concern to public health. The next slides will discuss 4 of them: environmental epidemiology, social epidemiology, community epidemiology, and forensic epidemiology.
Environmental epidemiology is the study of how human health is influenced by environmental factors (Friis & Sellers, 2014.) This includes the study of zoonotic diseases, vector-borne diseases, water safety, occupational hazards, and exposure to carcinogens and teratogens (Virginia Department of Health, 2014.) Zoonoses are diseases that are transmitted from vertebrate animals to humans, such as rabies, psittacosis, Hantavirus, and cryptosporidiosis (Virginia Department of Health, 2013.) Vector-borne diseases, such as Lyme disease, malaria, and West Nile virus, are spread by blood-sucking arthropods like ticks and mosquitoes (Virginia Department of Health, 2015.) Environmental epidemiologists are crucial in developing strategies for control and prevention of both types of diseases, i.e. rabies vaccines for cats and dogs and mosquito control via elimination of standing water reservoirs (VDH 2013; VDH 2015.) Environmental epidemiology plays a role in ensuring that our water is free of chemical contaminants (such as heavy metals, industrial waste, and pesticides) and dangerous microorganisms like Giardia, toxic algal blooms, and Legionella spp. (Friis & Sellers, 2014.) This includes both drinking water and the water we use recreationally, such as lakes and pools (Friis & Sellers, 2014.) The CDC’s Waterborne Disease and Outbreak Surveillance System was established in 1971, and was originally intended to collect data on outbreaks of disease related to drinking water. It has since been expanded to include data from recreational water sources (CDC, 2015.) The EPA’s current drinking water regulations were made possible by data collected from the WBDOSS (CDC, 2015.) Occupational hazards are substances found in the workplace that cause disease in humans (Friis & Sellers, 2014.) These can include mineral and organic dusts (i.e coal dust), chemicals (i.e. organophosphates and solvents), and biological agents (i.e. HIV and hepatitis) (Friis & Sellers, 2014.) Environmental epidemiologists monitor the health and safety of work sites through surveillance programs (Friis & Sellers, 2014.) Exposure to carcinogenic and teratogenic substances, which can occur in the workplace as well as out of it, require careful attention. A carcinogen is an agent that is suspected of or proven to cause cancer, such as asbestos, benzene, ionizing radiation, drugs like etoposide and cyclophosphamide (used in cancer chemotherapy, ironically) and viruses like HPV and HIV (American Cancer Society, 2015.) Teratogens, on the other hand, are agents that are suspected of or known to interfere with fetal development, resulting in congenital malformations or fetal death (Purdue University, 2014.) Many drugs have teratogenic effects, including warfarin, thalidomide, testosterone compounds, and morphine sulfate (Purdue University, 2014.) Other teratogenic substances include cadmium, cannabis, Agent Orange, formaldehyde, and vinyl chloride (Purdue University, 2014.)
The focus of social epidemiology is on the factors within the physical and social environment that promote both health and disease (Healthy People 2020, 2014.) It assumes that the societal distribution of advantages (healthy food, quality education, safe housing, etc.) and disadvantages (poverty, low literacy, racism, etc.) reflects the distribution of health and disease within a population (Honjo, 2004.) The Healthy People 2020 initiative (2014) determined that there are 5 key areas of social determinants: education, economic stability, the social and community context, health and health care, and the neighborhood and built environment. These areas are not discrete; they often overlap and affect each other. For example, if an individual lives in poverty, there are increased difficulties with accessing quality educational facilities (which can be a consequence of the built environment; better schools may be physically out of reach. If an individual does not have access to quality health care, their health may suffer, which could lead to economic instability (i.e. job loss.) Healthy People 2020 (2014) seeks to bolster up these 5 key areas by reducing poverty rates, increasing high school graduation and college enrollment rates, promoting safe and affordable housing, ensuring that everyone has health insurance and a primary care provider, reducing crime and violence rates, and eliminating racism and discrimination.
While epidemiology is used to evaluate the health of populations in general, it can be narrowed down to a more specific focus. Community epidemiology is very effective at evaluating the health needs of a singular community, whether it be a neighborhood, town, or city (Friis & Sellers, 2014.) By involving community leaders and/or representatives, epidemiologists can identify what the community feels are its most pressing problems (Friis & Sellers, 2014.) If, for example, an epidemiologist was doing a study on breast cancer in state A, and city B has had no breast cancer diagnoses, but has had a cluster of pancreatic cancer diagnoses, then it would be worthwhile to work with city B to determine the cause.
In the aftermath of the 9/11/01 terrorist attacks, which included anthrax-laced letters to politicians, the threat of a full-scale bioterrorism event became very real. The CDC (2012) created a training module on forensic epidemiology, which was intended to be presented to both public health and law enforcement personnel. Forensic epidemiology utilizes traditional epidemiologic methods in order to investigate potentially criminal public health threats (Freeman, 2013.) A forensic epidemiologist works closely with law enforcement officials, and often serve as consultants and expert witnesses (University of North Carolina, n.d.) One of the first instances of a bioterrorism investigation in the US was in 1984, when 751 residents of The Dalles, Oregon contracted salmonellosis (Goodman et al., 2003.) It was determined that members of a religious cult deliberately contaminated salad bar food with salmonella bacteria in an attempt to influence voter turnout (University of North Carolina, n.d.) 2 members of the sect were later indicted on charges under the federal antitampering act (Goodman et al., 2003.)
Diseases and other states of health can be looked at from both a clinical and epidemiological perspective. In general, the clinician will focus on the individual who has a given disease – their symptoms, their activity prior to becoming sick, laboratory findings, and how best to treat that one patient (CDC, 2012.) In a 2013 study, Ravel et al. looked at 3 common parasitic diseases from both a clinical and epidemiological perspective; one of these was giardiasis. They noted that the clinical presentation of giardiasis included abdominal pain, bloating, dehydration, watery diarrhea, fatigue, nausea and vomiting (Ravel et al., 2013.) The median duration of illness was 21 days (Ravel et al., 2013.) Treatment of the disease was not specified in the study, but the Mayo Clinic (2012) states that treatment for giardiasis includes antiparasitic drugs such as Flagyl, and supportive care as necessary.
On the other hand, epidemiology’s focus is on the community (CDC, 2012.) The epidemiologist will look at how many people in the community are experiencing a health problem and will attempt to trace the source of the outbreak (CDC, 2012.) They will collect data on each person’s activities prior to getting sick, and look for a pattern (CDC, 2012.) In the same study referenced on the previous slide (Ravel et al., 2013), the researchers found that 176 people contracted giardiasis between June of 2005 and May of 2009, resulting in a crude incidence rate of 8.8 per 100,000. Out of all the cases, 52% had recently traveled within Canada, 43% reported being in contact with household pets, and 44% reported recent swimming (Ravel et al., 2013.) The CDC (2012) notes that individuals who come into contact with infected animals or water, as well as traveling where giardia is endemic, have the highest risk of being infected with the parasite, which aligns with the results generated by Ravel et al. (2013.)
If you’re interested in learning more about epidemiology, there are many online resources you can use. Coursera is an online platform that allows you to take short courses in a multitiude of subjects for free. The epidemiology course is taught by Dr. Karin Yeatts and Dr. Lorraine Alexander, both from the University of North Carolina at Chapel Hill (Coursera, 2015.) Successfully completing the course allows you to earn a certificate.
Another excellent resource can be found at the CDC’s website. Their Division of Scientific Education and Professional Development offers this course, which is a reproduction of the textbook “Principles of Epidemiology in Public Health Practice, 3rd ed.: an Introduction to Applied Epidemiology and Biostatistics.” If you register for the course through http://www.cdc.gov/TCEOnline/, you can earn CE credit if you pass the post-test with a 70% or better (CDC, 2013.) Even if you aren’t interested in the CE credit, it’s a good read.
