Chapter 15: Human Infectious Disease

How dos an animal virus with DNA replicate? What are the steps?

(1) host cell membrane fuse with host cell viral envelope (entry) (2) viral capsid is uncoated by cell enzymes--> DNA enters cell's nucleus (3) new viral DNA is synthesized in the nucleus (4) capsid proteins are synthesized in cytoplasm (5) assembly of new viruses (viroids) (6) The viruses bud through the nuclear envelope, or plasma membrane and are released outside of cell to infect other cells

What is the story behind H1N1 flu (Swine virus)?

- 2010 type of Influenza A strain - victims have chils, fevers, sore throat, muscle pain, severe headaches, coughing= flu - causes many deaths worldwide, especially in kids - came from pigs---> transmitted to humans

What are some major reasons for the appearance of new diseases?

- Populations grow and expan into previously uninhabited areas - humans are exposed to insects and other animals that harbor infectious agents - worldwide transport of animals - increased international travel spreads disease to new areas - changes in food handling or processing (Mad Cow- infected beef carcasses used to make animal feed)

In the latter half of the 20th century, many infectious diseases seemed to be under control. What were some contributing factors?

- Use of antibiotics - development of vaccines - vigilant public health system - better sanitation - water purification - better hygiene education and practices

Are viruses living or non-living? Explain

-Non-living, lack enzymes and cellular structures for metabolism and growth -cannot reproduce without a host cell

What are characteristics of viruses?

-simplest of infectious agents -DNA or RNA as genetic material Surrounded by a protein coat called a capsid - may by covered by a membrane-like envelope

What are the characteristics of a bacteria?

-single celled -prokaryotic (no nucleus) - lack organelles found in human cells

What is an opportunistic pathogen?

A pathogen that only causes a disease when a host's defenses are suppressed Ex: A tiny parasite that lives in the intestines of humans and animals is responsible for cryptosporidiosis. Most people get the disease by drinking contaminated water or eating contaminated produce. Cryptosporidiosis is an unpleasant, diarrheal illness for healthy people. However, if you're HIV-positive it can last longer and cause more severe symptoms

What is occurring during the acme period of a disease?

Acme period = climax Very specific signs and symptoms Ex: Flu severe cough and muscle pain in chest, back and legs high fever and shaking chills ****Most contagious during this period!! STAY AWAY FROM OTHERS!!! (except if you have to miss Biology)

Compare the terms signs, symptoms and syndrome.

All refer to changes from a healthy state to a diseased state by altering body structures and functions. Sign= changes in body function that a physician can detect and measure (ex: temperature) Symptom= changes in the body that a patient experiences but cannot be seen by a physician (ex: feeling tired) Syndrome= a group of signs and symptoms Ex: AIDS viral disease- signs include diarrhea, loss of white blood cells and symptoms such as discomfort and fatigue

Name an infectious disease caused by a fungus.

Athlete's foot Oral thrush Diaper rash Yeast infectious Valley fever (respiratory disease)

Are bacteria living or non-living? Explain.

Bacteria are living because they can grow and reproduce on their own

What is bioterrorism? What are some potential bioterrorism organisms?

Bioterrorism= deliberate release of viruses, bacteria, or other germs used to cause illness or death in people, animals, or plants Organisms- Anthrax (US 2001) Smallpox Botulism- Bacterial toxins that can be added to food or water supplies

What makes bioterrorism attractive to terrorists?

Cheaper to produce than chemical and nuclear weapons, but just as deadly and dangerous

What does it mean to say a disease is an emerging infectious disease? Give an example.

Emerging infectious diseases- recently surfaced in a population Ex: AIDS, Lyme disease, Ebola hemorrhagic fever, mad cow disease, SARS, West Nile fever (in the Americas) and H1N1 (type of flu) known as the Swine Flu

Compare and contrast the following terms endemic disease epidemic disease Outbreak Pandemic

Endemic disease- spreads within a given region (plague in the US southwest) Epidemic disease- disease breaks out in explosive proportions within a population (Influenza, flu is often epidemic) Outbreak- more contains occurrence (measles in one US city) Pandemic- occurs worldwide (AIDS)

What are endotoxins? Give an example of a disease caused by a bacterial endotoxin

Endotoxins= lipid portion of the cell wall of many bacteria, released upon death of the bacterial cells - cause chills, fever, weakness and aches, general malaise -required in larger doses than exotoxins Ex: Salmonella, Typhoid fever

What are exotoxins? Give an example of a disease caused by a bacterial exotoxin

Exotoxins= protein molecules, often enzymes, released and transported throughout body, minute amounts, destroy cellular structures or inhibit metabolic processes Ex: Botulism Fun Fact- 1 pint of pure toxin could destroy entire human population

Besides bacteria and viruses, what other types of organisms can cause human infectious diseases?

Fungi- yeasts, mosts and mushrooms Protozoa- single cells eukaryotic organisms Helminths- parasitic worms Prions- proteins

What is a helminth? What are some common diseases involving helminths?

Helminth = parasitic worm Flatworms roundworms--pinworms Tapeworms roundworms--Elephantiasis (page 337 in book)

What is indirect transmission? 5 examples of how diseases could be transmitted this way

Indirect transmission- a person comes in contact with pathogens on inanimate (nonliving) objects *aerosols- pathogens that travel through air on air born particles (fine dust particles or moisture droplets) (Tuberculosis, SARS) * contaminated food (E.coli) * contaminated water ( * contaminated objects (fomites) * injection of contaminated soil * arthropod bites (mosquitoes, flies, fleas, lice and ticks)

Less than ___% of bacteria known to science cause disease. What do the Good Guys do for us?

Less than 1%- BACTERIA ARE GOOD - decomposers - help us digest food in our intestines - provide us with nutrients - protect us from pathogens

What is the most widespread infectious disease in the world?

Malaria- 1 million people killed each year, tropical regions, mostly children - protozoan Plasmodium lives in gut of Anopheles mosquito and is transmitted by a mosquito from infected person to a new host's blood--> enters liver cells, undergoes transformation--> penetrates RBCs--> disrupts RBC jobs - cycles of fever and chills

Virus or bacteria or both Can use an antibiotic to treat?

Only bacteria- because "anti-biotic" means against living organism. Bacteria are living but viruses are not.

Define parasite.

Parasite = organism that lives within the body of another, often causing some level of damage

Name an infectious diseased caused by a protozoan.

Pathogenic protozoans spend part of their life outside of humans, living in soil, water, or insects, or infecting other animals. Lyme disease Diarrhea (amoeba) Malaria Cryptosporidium

What is occurring during the period of convalescence?

Period of convalescence- body's systems return to normal

What is occurring during the period of decline?

Period of decline- signs and symptoms of disease subside - sweating is common, body releases excessive amounts of heat * still can transmit disease to others, pathogens exit the body (coughing, sneezing)

Describe three direct methods of disease transmission.

Person to person- Diseased person (or animal) to non-diseased person *air borne, *hand or object contact, *sexual contact, *kissing, *blood transfusions, *mother to fetus *Respiratory droplets (coughing and sneezing) *Contact with animals (rabies)

What is a prion? What disease do they cause?

Prion= misfolded protein that induce other proteins to become misfolded, leading to disease (usually in the brain) virus-like Mad cow disease

What are some of the reasons for reemerging diseases?

Reasons- antibiotic resistance, lower immunity (AIDS patients), l ax public health programs (unvaccinated individuals) Climate change- spreads to areas that are warmer than in the past

What does it mean to say a disease is reemerging?

Reemerging diseases existed in the past but are now showing a resurgence in frequency or geographic range

Give an example of a reemerging disease.

Reemerging diseases- Cholera Tuberculosis (TB)--- antibiotic resistance Dengue fever

Fun Fact (not really fun) What historic pandemic caused the most deaths?

Smallpox- 300-500 million (1900-1977) Currently, there is no evidence of naturally occurring smallpox transmission anywhere in the world. Although a worldwide immunization program eradicated smallpox disease decades ago, small quantities of smallpox virus officially still exist in two research laboratories in Atlanta, Georgia, and in Russia (yikes!!)

The prodromal phase of a disease may be classified as subclinical or clinical. Compare subclinical disease to a clinical disease

Subclinical disease- has few obvious symptoms Clinical disease- symptoms are apparent, mild to severe, depending on the pathogen

What is the Germ Theory of Disease and who are the authors of this theory?

The germ theory of disease states that many diseases are caused by microorganisms. These small organisms, too small to see without magnification, invade humans, animals, and other living hosts. Their growth and reproduction within their hosts can cause a disease. Louis Pasteur and Robert Koch are the authors.

Some bacteria cause disease by producing toxins. What are toxins?

Toxins= microbial proteins Two types- Endotoxins and exotoxins

What is being proposed as the best weapon against bioterrorism?

Vaccines! As of 2003 the US has stockpiled sufficient smallpox vaccines to vaccinate entire population

What is a vector?

Vector = organism that transmit protozoa from one person to the next Ex: mosquitoes, ticks, turtles, snails.

Define contagious

any microbe that can be readily transmitted from one organism to another

Define infectious

any microbe that invades and grows in the tissues of the body

What is occurring during an incubation period of a disease?

incubation period= time between exposure and appearance of the first symptom (Ex: flu 2-3 days) determined by number of organisms that enter the body, rate of replication, level of host resistance

Define pathogen

microbes that cause disease

Define pathogenicity

pathogenicity= ability of a microorganism or virus to gain entry into the host's tissues and then bring about a physiological or anatomic change that results in poor health Greater pathogenicity---> greater number of individuals infected Lesser pathogenicity---> lesser individuals infected

What is occurring during the prodromal phase of a disease?

prodromal phase= fairly general symptoms, indicating a competition between pathogen and host has begun (Ex: Flu fever, headache, and tiredness)