Infectious DiseasesChapter 20, section 2

Disease is a major focus of environmental health

Two categories: • transmissable (or infectious) disease – can

spread from one person to another; ex. malaria, flu, TB

• nontransmissable disease – cannot be transmitted from one person to another; ex. cancer, heart disease, respiratory disorders

Despite our technology, disease kills most of usDisease has a genetic and environmental basis

– Poverty and poor hygiene can foster illnesses

Q1. What is the difference between a transmissible and nontransmissable disease? Q2. Give two examples of each.Q3. What are the top three leading causes of death worldwide, according to the pie graph at right?

Infectious diseases kill millions• Infectious diseases kill 15 million

people per year– Half of all deaths in developing

countries– Developed countries have better

hygiene, access to medicine, and money

• Vector = an organism that transfers pathogens to a host (Ex: mosquito, snail, fly)

• Pathogen – something that causes disease (bacteria, fungus, virus)

Q4. Refer to the figure above. What are the six deadliest infectious diseases for people in order of the number of deaths they cause each year?Q5. Define and give an example of a pathogen.Q6. Define and give an example of a vector.

Viruses HIV(AIDS)

Hepatitis B

Smallpox

Ebola

On this scale, a human hair would be 6 meters (20 feet) wide

1 micrometer

Bacteria Vibrio cholerae(cholera)

Myobacteriumtuberculosis

(tuberculosis)

Treponema pallidum (syphilis)

6 micrometers

Protozoa

Plasmodium(malaria)

10 micrometers

Q7. List four pathogens that are viruses.Q8. List three pathogens that are bacteria.

Pathogens that cause disease:

Ways infectious diseases spreadPathogens can infect people through different routes: • Through the air• Through contaminated water• Through contaminated food• By a vector• Through the skin• From mother to fetus/newborn• By contact with an infected person’s bodily fluidsQ9. List a disease caused by each of the above

transmission routes. You may use your disease flashcards.

How do the cause of deaths for rich and poor countries compare?

Lung cancer

Q10. List the top three causes of death for high income countries. Are any of these infectious diseases? If so, which ones?

Q11. List the top three causes of death for low income countries. Are any of these infectious diseases? If so, which ones?

What factors have reduced infectious disease in high income countries?

• Vaccinations• Better sanitation – clean water• Antibiotics and other medicines

Q12. Can you list four infectious diseases that YOU have been vaccinated against?

Q13. What type of pathogen is affected by antibiotics?

Anopheles mosquito (vector)in aquatic breeding area

1. Femalemosquito bitesinfected human,ingesting bloodthat containsPlasmodiumgametocytes

4. Parasite invadesblood cells, causingmalaria and makinginfected persona new reservoir

3. Mosquito injects Plasmodiumsporozoites into human host

2. Plasmodiumdevelops inmosquito

eggs

larvapupa

adult

“Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die. In 2010 an estimated 219 million cases of malaria occurred worldwide and 660,000 people died, most (91%) in the African Region.”(CDC website)

Q14. What vector carries malaria? Q15. What organism infects the blood and actually causes malariaQ16. What are the symptoms of malaria?

How to reduce malaria –• Eliminate breeding grounds for mosquitos (reduce standing water)• Kill mosquitos with insecticides• Avoid getting bitten – use insect repellent and mosquito nets for sleeping• Take anti-malarial drugs if traveling to areas affected by malaria

Q17. How could an individual protect themselves from getting malaria?Q18. How could a community reduce the number of cases of malaria?

Many diseases are increasing

• Tuberculosis, acquired immunodeficiency syndrome (AIDS), and the West Nile virus have increased in recent years

• Our mobility spreads diseases – the more globalization occurs, the more people travel and contact other people

Q19. List three infectious diseases that are increasing worldwide.Q20. When did the highest number of cases of West Nile virus occur in the U.S.? What part of the U.S. had the disease first?Q21. How does globalization affect the spread of disease?

Some diseases cross from animals to humans

Avian flu – people in Asia who work with live birds (ducks, geese) can get the virus

Swine flu – also called H1N1

Q22. Name two animals from which people can contract a type of flu virus.

Current issues with infectious diseases• Drug-resistant strains of bacteria have

developed in response to the increased use of antibiotics

Q23. Using the diagram above, explain how the final population became more resistant after the use of an antibiotic.

Q24. MRSA, a drug-resistant form of staph bacteria, was ___% resistant to antibiotics by 2001.

Original pop treated with antibiotic:

Current issues with infectious diseasesClimate change will expand the range of

diseases

Q25. How could warmer global temperatures affect the spread of diseases such as dengue fever and malaria, which are spread by mosquitos?

Solutions

Infectious Diseases

Increase research on tropicaldiseases and vaccines

Reduce poverty

Decrease malnutrition

Improve drinking water quality

Reduce unnecessary use of antibiotics

Educate people to take all of anantibiotic prescription

Reduce antibiotic use to promotelivestock growth

Careful hand washing by allmedical personnel

Immunize children against major viral diseases

Oral rehydration for diarrhea victims

Global campain to reduce HIV/AIDS

Q27. One textbook says that this is the best weapon to fight the spread of viruses. Write down the solution that the arrow indicates.

Q26. List five ways to prevent or reduce the incidence of infectious diseases throughout the world.

BioterrorismFrom the CDC website:“A bioterrorism attack is the deliberate release of viruses,

bacteria, or other germs (agents) used to cause illness or death in people, animals, or plants. These agents are typically found in nature, but it is possible that they could be changed to increase their ability to cause disease, make them resistant to current medicines, or to increase their ability to be spread into the environment. Biological agents can be spread through the air, through water, or in food. Terrorists may use biological agents because they can be extremely difficult to detect and do not cause illness for several hours to several days. Some bioterrorism agents, like the smallpox virus, can be spread from person to person and some, like anthrax, can not. ”

Bioterrorism using pathogensQ28. What are six agents that could be used by bioterrorists? Q29. What are two ways to reduce threats from bioterrorists?

Category A B C

Definition

Pose the highest risk to national security because they•Can be easily disseminated or transmitted from person to person•Result in high mortality rates•Have potential to cause public panic and social disruption•Require special preparedness actions

Pose the second highest risk because they•Are moderately easy to disseminate•Result in low mortality rates•Require enhancement of diagnostic and surveillance capability

Emerging pathogens that could be engineered for mass dissemination because they:•Are available•Are easily produced and disseminated•Have potential for high mortality rates

Examples

•Anthrax•Botulism•Plague•Smallpox•Tularemia•Viral hemorrhagic fevers (e.g. Ebola, Marburg)

•West Nile Virus•Caliciviruses•Hepatitis A•Ricin toxin•Salmonella•Diarrheagenic E. coli

•Influenza•SARS•Rabies•Multi-drug resistant tuberculosis

•Yellow fever•Tickborne hemorrhagic fever