Epidemiological Concepts

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Epidemic

Example- Cholera disease has caused epidemic outbreaks in many underdeveloped countries and occurs through eating/drinking contaminated food or water with the feces of someone infected with the disease. This is a bacterial disease caused by Vibrio Cholerae and is common in many countries such as Africa, Southeast Asian, and South/Central America. Once this bacteria is contracted, you experience watery diarrhea, vomiting and dehydration. This disease often does not spread from person to person, but through poor hygiene, lack of proper water supplies or sewage disposal, and sometimes the consumption of raw or contaminated seafood from places that may be exposed to feces contamination. Because of this, there is often a large and quick spread throughout vulnerable populations such as refugee camps, urban slums, people living in unsanitary conditions, and population displacement for reasons such as natural disasters or wars. This is why cholera is classified as an epidemic, due to the sudden outbreak of the bacteria in a specific geographic area. When there is unsafe drinking water or contaminated food, everyone living in those areas are affected, as food and water are essential for life. So, after an event such as a natural disaster, many people are forced into a crowded area and all their food and water is infected with the cholera bacteria. During the industrial revolution in the 19th century, the rapid urbanization and industrialization caused the living conditions to decline for many people, and led people to overcrowded areas, often lacking proper sanitation, which started an outbreak of cholera. Additionally throughout colonialism, Europeans failed to address or meet the sanitation needs of their colonies, which caused many outbreaks in Africa, Asia and the Caribbean during this historical period. Currently there is an estimated 1.3-4 million cases of chorea each year, resulting in anywhere from 21, 000- 143, 000 deaths.

Public Health Measures- For the cholera epidemics, protection from public heath is the most useful in stopping an outbreak. Public health will provide clean drinking water to areas affected with cholera, put in place a water treatment plant or distribute chlorine tablets to clean the water. They may also provide oral rehydration therapy and solutions to prevent the death that occurs as a result of cholera. Since the root cause of cholera spreading comes from lack of proper sanitation, Public health focuses on proper waste disposal as well, to ensure it stops contaminating water and food and slows the spread again.

Epidemiological significance- Since epidemics occur as a result of a deviation from normal pattern, and usually indicate changes in behaviour, new mutations or environmental disruptions they take a huge toll on health care systems. Since they are usually unpredictable, it is hard to come up with all the necessary resources needed to treat, diagnose and halt the spread. Facilities, healthcare workers and staff are often overwhelmed with the quick unexpected spread of disease in their area, leading to a high rate of morbidity and mortality.

Definition- This refers to the rapid increase in a disease that is contained in a large population, such as a country, similar to a disease outbreak in a smaller area. Epidemics are often unexpected and above the normal or predicted rate of increase in a specific area. Epidemics affect large populations in short periods of time due to their rapid growth.

Pandemic

Example- Covid-19 began because of the SARS-CoV-2 virus in Wuhan China, and eventually led to a global pandemic, lasting since 2020-present. Although the severity has now decreased, it was a worldwide issue for about 2 years, affecting schools, workplaces and everyday life. This disease is transmitted mainly through respiratory droplets which were produced by sneezes, coughing and talking. It also transmitted through touching contaminated surfaces and then touching your face, eyes and mouth. Symptoms of covid-19 include fever, chills, dry coughs, shortness of breath, loss of taste and smell and runny or congested noses. This was a challenging disease to combat, as there was also an asymptomatic spread, transmitting this disease without even knowing you have it, and experiencing no symptoms. By 2024, there were over 7 million reported cases and 6.8 million deaths. This disease also mutated over time, leading to different variants, such as omicron and delta, which were even more transmissible. In the pandemic, everyone was affected, but it hit the hardest to those living in highly populated areas. It also was the hardest on people above the age of 65, which is where many of the deaths came from. This pandemic was one of the most significant events in the 21st century, affecting almost every aspect of life and the impacts are still being felt today.

Public Health Measures- The main pillar used in this situation to combat the pandemic was focusing on prevention and protection. Many protocols were put in place to reduce the transmission of the disease and there was a big focus on containment. Once diagnosed with Covid, public heath mandated a 2 week quarantine to slow down the spread. They also enforced a period where you were unable to go to school, and in office work was limited if possible. Once in public areas, for things such as grocery shopping, you were required to wear a mask and sanitize upon exit and entry. There was a huge emphasis on sanitization and keeping your distance from others, roughly 6ft to prevent the droplets from entering another persons area. Once we learned more about the disease they began to work towards a vaccine to fight the disease and prevent it from spreading. If you chose not to vaccinate, you were not allowed to travel, or attend many public events, which lead to 5.5 billion people to receive a dose of the vaccine. That is roughly 72.3 % of the whole world.

Epidemiological significance- Pandemics are a global devastation, and the impacts on society are lasting. As previously mentioned, pandemics are often a new strain, or occur due to a mutation, which leads to us not knowing enough about the disease and a lack of preparedness and ability to prevent. This often is why the effects last so long, as we are just learning more and more about the disease, how it spreads and who is most vulnerable. Pandemics are often out of control from the government and healthcare systems because they are on such a global scale. Since billions of people are affected with the disease, hospitals are overcrowded, staff are overworked, and everyday life is halted. Pandemics often show us faults in our surveillance and monitoring of diseases, as we were unable to contain the disease until it spread across the globe.

Definition- This refers to the disease spread worldwide, or through many countries, often lasting for a long time. Pandemics have high transmission rates, and usually occur as a result of new or highly contagious pathogens. Pandemics are often transmitted easily, often because of people, respiratory droplets, contaminated surfaces, and physical contact.

Epidemiological Concepts

Endemic

Example- Chagas disease is a neglected tropical disease which is caused by the protozoan Trypanosoma cruzi. This endemic occurs in 21 countries of the Americas, and it can spread through migration of infected people. This parasite is spread through the infected feces of the triatomine bugs, which are primarily found in Mexico, South America and Central America where it is warmer. This and the lifecycle of a triatomine bug, is how it can be classified as an endemic since the spread is localized and consistent due to the prevalence of this bug especially in the warmer months. Its secondary mode of transmission comes from blood transfusions, organ transplants or from mother to child through birth after someone has been infected. The feces of these bugs cannot penetrate the skin, but when they leave their droppings, they can enter through micro tears, leizions, and the eyes. There are many vulnerable groups which are more likely to contract this disease, especially people living in these areas with poorly constructed homes, allowing bug infestations. As an estimate, roughly 70 million people living in these regions are at risk of contracting this disease, due to the exposure to the bug and it causes nearly 10,000 deaths each year. Symptoms of this disease includes; enlarged glands, flu-like symptoms, rashes, appetite loss, swelling of the face or eyes and vomiting/diarrhea. This caused a huge burden on the healthcare system since millions are affected each year, with things such as chronic heart failure, gastrointestinal complications and arrhythmias as a result of the disease. Chagas disease was first described in 1909 by Carlos Chagas when he identified the parasite and the bug as the primary transmission. Through the 20th century Chagas became much more recognized, although it continued to be contracted due to rural communities with limited access to healthcare and pesticides. This also impacted immigration into the United States in the 80s and 90s as people were worried about the potential to spread this disease through blood transfusions and organ donation from people who came from these regions.

Public Health Measures- To prevent the spread of many endemic diseases such as Chagas, the main pillar Public Health focuses on is protection. As mentioned above, Chagas occurs as a result of the feces of a specific bug, so, Public Health decided to focus on improving living conditions to prevent exposure to these disease vectors. They sealed up cracks in the walls and roofs, to help with these bugs intruding into the homes of people who live in the same areas of these bugs. Public Health focused on protection from disease aging through the regulations and policy of blood screening, since we know this is a transmission of Chagas. Since there is no vaccine, which would be a preventative measure, public health focuses on stopping contraction of the disease altogether and protecting the populations from the vector of the triatomine bug.

Epidemiological significance- Understanding these types of diseases and tracking their numbers, as well as focusing on preventing outbreaks, and reducing transmission is important because this type of disease can greatly affect a society. Endemics can cause lower productivity in populations, due to this consistent strain on health and having to accommodate the large number of sick people each ‘cycle’. It also increases healthcare costs trying to treat endemic diseases on a consistent bases, also spending lots of money each time there is an outbreak.

Definition- Endemic refers to a disease that occurs consistently in a specific area, and is always present in the region due to environmental conditions, local practices or genetic predispositions. The spread of endemic diseases are often low and there is a chance that there are time periods where none of the population may be affected.