Environmental Health Services - Study Guide PDF

Module 6: Environmental Health Services A Comprehensive Study Guide 6.1: Infectious Disease Infectious disease: Disease caused by infectious agents such as viruses, bacteria, parasites, and fungi. o...

Module 6: Environmental Health Services A Comprehensive Study Guide 6.1: Infectious Disease Infectious disease: Disease caused by infectious agents such as viruses, bacteria, parasites, and fungi. o Reduction of infectious diseases due to advances in nutrition, antibiotics, immunization, food safety, housing, and sanitation. Infectious diseases such as smallpox, TB, syphilis, cholera, and plague are historically the leading cause of death. o Historical examples include the 1918 pandemic which resulted in 40 million deaths. Mechanism of Infection o When an organism enters the body, individuals fight it off with their immune system o Individuals more likely to develop disease have weak immune systems due to drugs, age, and preexisting conditions, or lack of vaccination. Stages of Infection o Incubation period describes the time from when someone gets infected to when symptoms start o Clinical stage- is marked by the onset of symptoms o Infectious period is the time during which the infected person can spread the disease Figure 1A: Stages of infection from exposure, incubation, clinical presentation, to recuperation. o Carriers- people may not have any symptoms but still be able to infect others o Case fatality- is a measure of the severity of a disease it is the proportion of people that die from being infected o Ex. if 6 out of 10 people with the disease die from it the case fatality is 60% o Basic reproductive rate- how infectious a disease is ▪ It is the average number of secondary cases because of one infected individual o Secondary attack rate- is the proportion of people who are exposed to the disease that develop an infection o Infectious disease types: ▪ Zoonotic disease- diseases of animals that can transmit to humans Ex. 60% of human infectious diseases are Zoonotic Zoonotic diseases include leptospirosis (mice), toxoplasmosis (cats), Campylobacter (chicken), and rabies o Emerging infectious disease- disease that appears for the first time or one that may have existed previously but is rapidly increasing in incidence or geographical range. ▪ Ex. Ebola, MERS CoV, Hendra, new influenza strains o Neglected Tropical Diseases- affects poorest countries ▪ Ex. Leishmaniasis, Trachoma, sleeping sickness, Schistosomiasis Figure 2A: Choropleth world map of the distribution of “neglected” diseases in the world.  Vector Borne Diseases- are transmitted from another infected animal or human to another person through the bite of a vector o Ex. Mosquito, ticks, fleas o Vector Borne Diseases- Malaria, Dengue, sleeping sickness, schistosomiasis o Vector-borne diseases are responsible for over 17% of all infectious diseases and cause a million deaths a year Means of Transmission o Vectors: ubiquitous insects/animals whose bodies are hosts for microorganisms ▪ Ex: malaria spread via mosquitoes o Aerosols: water droplets produced when infected person coughs or sneezes ▪ Ex: prevented by facemasks during COVID o Fecal-oral route: fecal matter from infected person reaches the mouth of an uninfected person, usually due to poor hygiene and contaminated water ▪ Ex: cholera-containing sewage system contaminated the water pump system in Soho, London o Carrier state: infected person who is totally asymptomatic can still infect others ▪ Ex: Typhoid Mary was a cook in NYC who had typhoid fever but didn’t show any symptoms, yet all her clients developed the disease Chain of Infection: public health initiatives usually target one or more of these to stop spread of disease o Link 1: Pathogen ▪ Virus, bacterium, or parasite that causes the disease in human o Link 2: Reservoir ▪ Living or nonliving place when pathogen lives and multiplies Ex: racoons are the reservoirs for rabies, days-old food is the reservoir for mold spores o Link 3: Method of transmission ▪ Action in which pathogen leaves reservoir and enters new host Ex: flea bites, sexual intercourse, drinking contaminated water o Link 4: Suseptible host: non-immune animal (for our purposes, humans) who have the pathogen transmitted into their bodies ▪ Chances can be reduced by immunization to pathogen ▪ Epidemiologic surveillance: consists of quarantining, contact tracing Breaking the Chain of Infection o Once all the qualities of the disease are identified, breaking the chain of disease requires that one aspect of the spread is controlled and contained, preventing the transfer of illness through each of the means of transmission. Deciding where to break the chain of infection depends on where the disease is most vulnerable, where the effort is most effective, or the risk associated with each link in the chain. Figure 3A: Visualizer of the chain of infection. Breaking Link 1: Targeting the pathogen o Antibiotic and antiviral treatments are effective means of containing an outbreak at its source, preventing infection of additional hosts. Breaking Link 2: Removing the reservoir o Identifying nutrients required by a disease and the ideal reproductive conditions for that pathogen ensure that the disease has no means of reproduction, preventing the spread in a Breaking Link 3: Isolating the means of transmission o Efforts such as quarantining affected individuals serve as effective means of breaking the means of transmission link in the chain of transmission.  Breaking Link 4: Preventing transmission from being effective o Administering vaccines is an effective way of keeping populations safe by preventing transmission from having an impact. Breaking Additional Chains: Considering special cases o In unique pathogen transmission cases such as malaria, where skin could be considered an additional chain, the chain of infection could be labeled “skin,” and breaking it could look like wearing long sleeves. Modern perspective: Breaking the weakest link o Surveillance systems locate individuals who have had contact with a pathogen and aim to administer treatments. o Contact tracing is a common means of preventing the spread of sexually transmitted diseases, allowing public health officials to alert those who have been affected and administer the appropriate treatments. o The syphilis tracking system in the prison system is the most well-developed example of the contact tracing system. When one inmate is exposed to the disease, they are asked to identify sexual contacts, who are notified anonymously and then treated appropriately. 6.2: Infectious Disease What is the One Health approach? o Article: What is One Health? ▪ What is One Health? A method of public health that links the well-being of animals in our shared environment with that of human health As more humans encroach on natural land, we are growing closer in contact to animals, which provides more opportunities for diseases to be transmitted between us o Movement of people and animals are influenced by deforestation, immigration, travel, trade, and purchase of domestic animals From this, we see a rise of zoonotic diseases o Ex: rabies, salmonella, West Nile virus, anthrax, Ebola, etc. ▪ Local animals’ health is usually a good indicator of whether human health is at risk Ex: birds die of West Nile Virus before humans do Figure 5A: Flow map of how interconnected humans and local animals’ health are. What are common One Health issues? o Anti-microbial resistant germs: makes it harder to treat some infections in people + animals o Vector-borne diseases: mostly at-risk in hot climates o Diseases in food animals: mostly implicates restaurants + produce o Human-animal bond: can improve well-being of both humans and domestic animals o Contamination of water: used for drinking + recreations