PUBH 201 Chapter 9

Pandemic

an epidemic that has spread over several countries or continents, usually affecting a large number of people.

Chain of Infection

1. Pathogen. The pathogen is a virus, bacterium, or parasite that causes the disease in humans. 2. Reservoir. The reservoir is a place where the pathogen lives and multiplies. Some pathogens spread directly from one human to another and have no other reservoir. Others, however, may infect nonhuman species, spreading from them to humans only occasionally. Plague, for example, is a disease of rodents that is transmitted to humans by the bite of a flea. Rats are the reservoir of plague. Raccoons and bats are reservoirs for rabies, which spreads to humans only through the bite of a rabid animal. Contaminated water or food may also serve as reservoirs for some human diseases. 3. Method of transmission. The pathogen must have a way to travel from one host to another, or from a reservoir to a new host. The flea is a vector for plague, transferring the plague bacillus from rat to human by sucking it up when it bites the rat and then injecting it into a human host with a second bite. Food-borne diseases are transmitted when a person eats contaminated food; water-borne diseases are transmitted when someone drinks contaminated water. Many respiratory diseases are transmitted by aerosol. AIDS, syphilis, gonorrhea, and a number of other diseases are transmitted by sexual contact. 4. Susceptible host. Even if the pathogen gains entry, a new potential host may not be susceptible because the host has immunity to the pathogen. Immunity may develop as a result of previous exposure to the pathogen, or the host may naturally lack susceptibility for a variety of reasons. Most microorganisms are specifically adapted to infect certain species. Canine distemper virus, for example, does not infect humans. Even within species, susceptibility to specific viruses varies among individuals. Scientists have been puzzled why a very few people who have been repeatedly exposed to the human immunodeficiency virus (HIV) do not become infected; recent studies have found a genetic mutation that makes them resistant to the virus.

Ebola

A contagious viral disease originating in Africa caused by bats or other wild animals, It is transmitted by blood and body fluids and causes body organs and vessels to leak blood, usually resulting in death. Preventative measures include washing hand, be notified of certain areas, stay away from meat products if in area where it is prominent.

Pathogen

A microorganism that causes illness.

Reservoir

A place where a pathogen lives and multiplies before invading a noninfected person. Some pathogens infect only humans; some have animal reservoirs and infect humans only occasionally. Contaminated water or food may serve as a reservoir for waterborne or foodborne diseases.

Aerosols

A suspension of liquid particles in the air; many infectious diseases of the respiratory system are transmitted by pathogen-containing aerosols released when an infected person coughs or sneezes.

Vector

A vector is a non-human carrier of communicable diseases.

Human Immunodeficiency Virus (HIV)

Acquired immunodeficiency syndrome (AIDS) is caused by HIV, which damages the cells in the body's immune system so that the body is unable to fight infection or certain cancers. Prevention is through safe sex measures such as condoms, abstinence, etc.

Zika virus

Aedes mosquito, possible sexual, vertical transmission, methods such as using bug spray, long sleeves, pest control can prevent spread of virus.

Vector

An animal or insect that transmits a pathogen to a human host.

Influenza

An infectious disease caused by a virus that mutates frequently, causing new strains to spread around the world regularly. Vaccines are effective but must be changed each year.

Parasite

An organism that lives off another organism (called a host) but does not contribute to the welfare of the host.

What are some differences between infectious agents: bacteria, viruses, parasites, and prions?

Bacteria: A large domain of single-celled microorganisms that lack a nucleus or other membrane-bound organelles. Only a few cause diseases. Viruses: A very small pathogen that is not capable of independent metabolism and can reproduce only inside living cells. Parasites: An organism that lives off another organism (called a host) but does not contribute to the welfare of the host. Prion: An infectious agent composed entirely of protein that causes rare neurodegenerative diseases such as "mad cow" disease in cattle and Creutzfeld-Jacob Disease in humans.

What is the difference between infectious diseases and chronic diseases?

Communicable diseases are the diseases which passes from one individual to another individual. They are generally caused by some bacteria, viruses or any other pathogens. For example, malaria, AIDS etc. Non-communicable diseases are the diseases which does not spread from one person to another person.

Direct vs. Non Direct/ Indirect Transmission

Direct contact transmission occurs when there is physical contact between an infected person and a susceptible person. Indirect contact transmission occurs when there is no direct human-to-human contact.

Means of Transmission

Infectious diseases are spread by a variety of routes, directly from one person to another or indirectly by way of water, food, or vectors such as insects and animals.

Which infectious diseases have caused the most deaths?

Lower respiratory infections, diarrheal diseases, and TB.

Immunization

Stimulating immunity to an infectious disease by exposing an individual to a weakened or inactivated pathogen or a portion of the pathogen.

Herd Immunity

The resistance of a group to an attack by a disease to which a large proportion of the members of the group are immune.

Why has there been a reduction in infectious diseases?

This is due to the updating of public health organizations and standards that have a high level of sanitary processes, creation of vaccines, and overall hygiene measures.

Disease transmission: How are these diseases spread? How can we break the chain of infection (how can we stop the spread?) Tuberculosis (TB)

Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but they can also damage other parts of the body. TB spreads through the air when a person with TB of the lungs or throat coughs, sneezes, or talks. Can be prevented through early detection and isolation and quarantine of infected people.

How do vaccinations work?

Vaccines are weakened or killed versions of the foreign agent used to enable an individuals response to the real agent if encountered, usually doesn't get people sick.

Zoonotic Disease

a disease communicable from animals to humans under natural conditions; also know as zoonosis

Rabies

an acute viral infection that is most commonly transmitted to humans by the bite or saliva of an infected animal. Prevention of rabies can be vaccinating animals

Epidemiological Triad

agent, host, environment

Endemic

constant presence and/or usual prevalence of a disease in a geographic location.

Outbreak

same definition as an epidemic but is often used to describe a more limited geographic event.

Epidemic

sudden increase in the number of cases of a disease above what is normally expected.