Infectious diseases.

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ACTIVITY 1: Infectious diseases

Read the following text and complete the concept map on the next page:

Have you ever noticed how a cold seems to travel from one person to another? First, your friend gets sick. Then, your friend’s sister gets sick. Next, her best friend gets sick. Eventually, half the class is suffering with the same symptoms. When a disease outbreak affects many people, it is called an epidemic. The word “epidemic” comes from the Greek words meaning “common among the people”. When this common sickness grows to global proportions it is called a pandemic.

In the 16th century, most people believed that disease was spread by foul air. There were no microbes, germs, or viruses – just air that had lost its ability to keep people healthy. So strong was this belief, that the Italian phrase for bad air, “malaria” was used to identify a common blood disease. In a work entitled “On Contagion”, Girolamo Francastoro proposed in  1546 that epidemic diseases could be caused by seed-like entities trasferred by the air and able to infect healthy individuals. Laboratory data backing Francastoro’s work was slow to appear. In 1870 Louis Pasteur presented his

Germ Theory of Disease, implicating microbes as the cause of infectious disease.

In the mid and late 1800s, recovery from major surgery wasn’t common. Although crude surgical procedures worked, the patients often died of infections - a common report by surgeons was: “operation successfully but the patient died”. The English surgeon Joseph Lister decided to improve his patients’ chances of recovery by sterilizing his instruments and disinfecting the operating room. These procedures used carbolic acid and heat to destroy populations of potentially fatal microbes. As expected, the recovery rate of Lister’s patients improved dramatically.

Ignatz Semmelweis was a Hungarian contemporary of Joseph Lister. Like him, Semmelweis introduced the concept of sterilization and disinfection into the hospital environment. He realized that childbed fever had a lower incidence in patients cared for by midwives. Semmelweis inferred that the midwives’ frequent hand washing reduced the spread of the disease. To improve hospital conditions, he required medical attendants to wash their hands in chlorinated lime. This procedure lowered the incidence of childbed fever, and mortality rates immediately dropped from 18.3% to

1.3%.

In 1878 Robert Koch was studying the spread of anthrax and tuberculosis. From his observations, Koch compiled a set of postulates that outlined the procedure for uncovering an agent of disease:

1. The suspect microbe must be present in the diseased animal.
2. The suspect microbe must be isolated from the diseased animal and grown in pure culture.
3.  When the microbes obtained from the pure culture are introduced into a healthy animal, the animals must become diseased.
4. Microbes from the new host must be removed and compared with the suspect original microbes to confirm its role in disease.

(Modified from “The Biology corner.com”)

GLOSSARY OF TERMS

A disease outbreak = el brote de una enfermedad 

Foul = repugnante, nauseabundo

Phrase = locución 

Crude = rudimentario

Carbolic acid = ácido carbólico o fenol 

Childbed fever = fiebres puerperales

Chlorinated lime = cal clorada (blanqueador en polvo) 

To uncover = revelar, destapar

A pure culture = un cultivo puro (de microbios)

ACTIVITY 2: Health and disease

With your mate discuss and answer the following questions:

1. What is a disease?

2. What is the WHO?

3. What is an infectious disease?

4. List six examples of infectious diseases.

5. What is a pathogen?

6. What is an epidemic? And a pandemic? Give some examples.

7. What is the most common method to sterilize medical equipment?

8. What is a disinfectant? Can you give some examples of disinfectants?

9. Explain the difference between an antiseptic and a disinfectant. Can you give

some examples of antiseptics?

ACTIVITY 3: Types of disease

Classify the following diseases as infectious / non-infectious diseases. In the third column try to add some specific information from the box below.

rheumatoid arthritis       AIDS        rabies        goitre        diabetes            leukemia     anaemia      scurvy       depression         

cancer              syphilis       anorexia     measles      flu      

INFECTIOUS	NON-INFECTIOUS	DUE TO / SYMPTOMS

Degenerative disease / lack of iodine / cells growing without control / genetic disease / virus / sexually transmitted disease / obsessive fear of gaining weight / lack of vitamin C / bacterium / mental disease / autoimmune disease / high blood sugar levels / a change in your emotional state / metabolic disease / inflammation of joints