How would a zombie apocalypse work Notes PDF

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margaret hoyt, zombie lecture 4...

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Zombie Characteristics ● Zombies have a one track mind and only think about one thing: Consumption ● Zombies only take what they want (typically brains). They are not productive members of society ● Zombies gather in large hordes that roam the streets, terrorizing hardworking citizens ● The zombie virus is highly contagious. Once exposed, it is very difficult (if not impossible) to be cured. ● Zombies have an insatiable appetite and will stop at nothing to feed their cravings ● Once a zombie outbreak occurs, it is incredibly difficult to regain order and normalcy ● Zombies don’t make a lot of sense when they speak. They have a severe lack of communication skills.

What disease causing agent would create a zombie? ● ● ● ● ● ●

Bacteria Virus Fungus Prion Parasite Other

Bacteria ● Microscopic single-celled organisms that thrive in diverse environments ● They can live within soil, in the ocean and inside the human gut ● Humans’ relationship with bacteria is complex. Sometimes they lend a helping hand, by curdling milk into yogurt or helping with our digestion. ● At other times they are destructive, causing diseases like pneumonia and MRSA.

Viruses ● Depend on the host cells that they infect to reproduce ● When found outside of host cells, viruses exist as a protein coat or capsid, sometimes enclosed within a membrane ● The capsid encloses either DNA or RNA which codes for the virus elements. While in this form-outside the cell, the virus is metabolically inert.

Fungus ● Any of about 99,000 known species of organisms of the kingdom Fungi, which includes the yeasts, rusts, smuts, mildews, molds, and mushrooms. ● There are also many fungus-like organisms, including slime molds and oomycetes (water molds), that do not belong to kingdom Fungi but are often called fungi. ● Fungi are among the most widely distributed organisms on Earth and are of great environmental and medical importance. ● Many fungi are free-living in soil or water; others form parasitic or symbiotic relationships with plants or animals.

Prions ● Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. ● They are distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response. ● The term "prions" refers to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain. ● The functions of these normal prion proteins are still not completely understood. The abnormal folding of the prion proteins leads to brain damage and the characteristic signs and symptoms of the disease. ● Prion diseases are usually rapidly progressive and always fatal.

Parasites ● A parasite is an organism that lives on or in a host and gets its food from or at the expense of its host. ● Parasites can cause disease in humans. Some parasitic diseases are easily treated and some are not. ● The burden of these diseases often rests on communities in the tropics and subtropics, but parasitic infections also affect people in developed countries

Other Considerations ● If zombie infection were transmissible person to person, how fast would it spread? ● What would be the mode of transportation? ● Can it be contained? ○ Isolation ○ Quarantine ● What are other possible control measures?

Epidemiology Defined ● Epidemiology comes from the Greek words ● Epi (upon) + demos (people) + logy (study of) ● Epidemiology is defined as the study of the distribution and determinants of health and diseases, morbidity, injuries, disability, and mortality in a population ● It implies that diseases or injuries, etc don’t “just happen” that there are specific patterns and trends to events ● The epidemiologist’s job is to uncover those patterns

Epidemiology

● It is not only involved in the study of the distribution and determinants of health-related states or events in human populations ● Also involved in the application of findings to prevent and control health problems ● Epidemiology can identify who is most at risk for an event ● Where the disease is most common ● When does it occur ● What programs might be most effective to prevent and control the event/disease

Activities that Epidemiology is involved ● ● ● ● ● ● ● ● ● ●

Identifying risk factors for a disease, injury, or death Describe the natural history of a disease (etiology) Identify individuals or populations at most risk Identify where the problem is located Monitoring conditions over time Evaluating the effectiveness of programs Provide information for planning of health programs Assist in the implementation of programs Being a subject matter expert Communicating public health information (interpretation)

The Epidemiology Triangle ● Agent: what is the cause ● Host: human/animal that harbor the disease ● Environment: what conditions exist to allow for disease transmission

Ro ● Ro= rate of reproduction ● In epidemilogy Ro denotes the average number of secondary cases of an infectious disease that one case would generate in a completely susceptible population ● Can be expressed mathematically as: ○ R=cpd ■ c is the number of contacts per unit time, ■ p is the transmission probability per contact, and ■ d is the duration of infectiousness. ● The R number will, of course, depend on a large number of factors, ● including: ● How the infectious organism is spread? ● Behaviors which affect the likelihood of spread ? ● (social mixing, sexual and feeding practices...) ● The level of susceptibility within the population depends on factors ● such as: ○ Prior immunity ○ Levels of nutrition and immune suppressions ○ Age

Modes of Transmission ● ● ● ● ●

Respiratory Direct contact food/waterborne Fomites Vectors

Incubation Period ● ● ● ● ● ● ● ●

The time from expoure to development of disease Each disease causing agent has a different incubation period Some are similar Range from minutes to months to years Critical concept for health Ideally we would want to interrupt transmission within 1 incubation period This would prevent secondary transmission in most cases Can you transmit disease prior to having signs and symptoms?

Epidemiological Triangle ● Diseases do not “just happen”; rather, there is a distinct pattern of events that occurred to allow people to become infected ● The epidemiological job is uncover that pattern and interrupt or break a link to stop transmission and subsequent morbidity and/or mortality

Other Challenges ● Sub-acute infections ● Is there like a percentage of people who are infected but have no clinical signs or symptoms and are still able to spread the infection ● Carriers ● People who are continually or intermittently she the infection causing agent but aren’t clinically ill?

Other Considerations ● Is there an intermittent host for the disease? ● Are there multiple modes of transmissions

Characteristics ● As an epidemiologist you always orient the data by: ○ Person ○ Place ○ Time

● Person: ● Who is getting the disease? ○ Age ○ Gender ○ SES ○ Education ○ Occupation ○ Race/ethnicity ● Place: ○ Where are people getting infected? ○ Did they all eat at the same restaurant? ○ Do they all live in the same neighborhood? ○ Were they all downtown for an event? ● Time: ○ What was the exact time signs and/or symptoms first appeared? ○ When did you eat the meal? ○ Can be seasonal variations ○ Can be cyclic variations ● Who, What, Where, When = Descriptive epidemiology ● The “What” can be any number of things including: ● What sign or symptom occurred first ● Where did it occur ● What came next ● Are people convalescing? ● Are they dying quickly or lingering

Control Measures ● What can we put in place to stop or reduce morbidity and mortalitiy? ○ Vaccines ○ Antimicrobials ○ Closure ○ Isolation ○ quarantine

Does it work? ● You decided that it appears that everyone who ate at the campus center became ill and you can’t find the source, so you close the campus center. ● What happens if the outbreak keeps going? ● What happens if the outbreak stops?

Building the Scientific Knowledge ● Reporting your findings is important ● This builds the scientific field of the disease and uncovers the etiology of the disease ● Once you understand the etiology you can break a link in the epidemiological triangle.

Summary ● ● ● ● ●

Epidemiology is a complex and challenging science Some diseases are predictable Other diseases just emerge or re-emerge and then disappear Infectious diseases have been around since before humanity Always looking for what’s coming next

Discussion Post Question: What is the incubation period and why is it biologically necessary? Why would it be important for an epidemiologist to know this information when investigating an outbreak? Answer: The incubation period is the time from exposure to development of symptoms of the disease, and the incubation period varies from species to species. It is biologically necessary because different diseases will start to show symptoms at different lengths of time. They can range from minutes to months to years. Food bourne illness, such as salmonella has a short incubation period versus mad cow disease has an incubation period of years. During the incubation period, you do not know that you have the disease because you have not started showing symptoms. This is important for epidemiologists because it is very critical for disease prevention. We would normally want to disrupt the transmission of the disease within 1 incubation period, because this would prevent secondary transmission in most cases. If an epidemiologist is able to target the incubation period time, it would help them in order to stop the spread of the disease. An epidemiologist can study to length of incubation periods of a particular disease to know what actions to take. For example, they can know to quarantine someone if the know that they were possibly exposed to a particular disease, and that could potentially stop that disease from recurring....