1. Infection and disease

2. Infection and disease
Infection: Entry of “infectious” organisms inside the body, their multiplication
Disease: Cell / tissue damage, signs and symptoms
All infections may not necessarily cause disease

3. Microbes come in different shapes and sizes
Protozoa
Bacteria
Viruses
Fungi
Parasites

4. Historical perspective

5. Evidence from mummies Egyptian pharaoh Ramses V
Unknown child from Naples
Source:

6. Egyptian art tells us about polio
Source: The Art Archive at Art Resource, NY

7. Supernatural explanations for infectious diseases
Climate, soil etc believed to make one sick
Source: Infectious Disease Epidemiology, Nelson and Williams

8. Hippocrates Dismissed supernatural explanations
Seasonal changes in disease patterns
Fever and swelling – immune response
Hippocrates ( BC)

9. Fracastoro
First to propose that infectious diseases were caused by invisible, minute, self-replicating seeds
Proposed transmission by direct contact, air and through objects
Described several infectious diseases including syphilis
( )

10. Renaissance era in medicine (14-17 century)

11. Foundations of modern medicine
Anatomy
Physiology
Circulation
Brain
Surgical instruments
hygiene

12. Hospitals and hygiene

13. First microscope (1600s)
Focus
Sample
Lens
Leeuwenhoek

14. First vaccine Edward Jenner (1749-1823)
World’s first vaccine – against small pox
Father of immunology

15. Louis Pastuer (1822-1895) Fermentation Pasteurization
Vaccine development

16. Robert Koch (1843-1910) Koch’s postulates
Gold standard in microbiology
Fathers of Microbiology
- Robert Koch
- Louis Pasteur

17. Koch’s postulates
First set of rules on how to link a disease to an infectious agent. Still used

18. Several bacterial agents were discovered in the 1800s
Year
Disease/organism
1874
Leprosy
1882
Cholera streptococcus
1884
Diptheria
Typhoid
Tetanus
1892
Gas gangrene
1894
Plague

19. Self-experimentation to prove Koch’s postulates
Inoculate organism into one’s own body to prove disease etiology / pathogenesis
Yellow fever / hookworms / Hepatitis E virus

20. Reservoirs and vectors
Transmission of plague from rats to humans
Transmission of yellow fever through Aedes aegypti
First established viral disease with obligate cycle in insect
no human to human transmission
Transmission of malarial parasite (Plasmodium falciparum through Aedes aegypti)

21. Disarming the microbe
Alexander Fleming discovered penicillin in September 1928.
World’s first antibiotic
“That’s funny”

22. Penicillin: Miracle cure

23. Terminology…
Incidence Fraction of a population that newly contracts a disease during a specific time. (Eg. Influenza virus)
Prevalence Fraction of a population having a specific disease at a given time. (eg. HIV)
Endemic disease Disease constantly present in a population. (eg. Malaria)
Epidemic disease Disease acquired by many hosts in a given area in a short time. (Eg. Dengue epidemic in Delhi)
Pandemic disease Worldwide epidemic (eg. Influenza pandemic).

24. Major pandemics Bubonic plague (1347-1351): ~ 200 million dead
Influenza ( ): ~ 100 million dead

25. Control of infectious diseases: 20th century
Foundation of the Center for Disease Control and Prevention (CDC)
Understanding disease biology/pathology
Development of molecular microbiology
Development of vaccines
Development of antimicrobial drugs

26. Development of vaccines
Year
Disease/organism
1798
Smallpox
1896
Cholera
1897
Plague
1927
Tetanus
Tuberculosis
1955
Polio
1970
Anthrax
1998
Rotavirus
Source: Infectious Disease Epidemiology, Nelson and Williams

27. Discovery of antimicrobial drugs
1928 – penicillin
1928 to 1962: 15 classes of antibiotics

28. Control of infectious diseases
1900: Annual Morbidity
2000: Annual Morbidity
Percent decrease
Smallpox
48164
100
Polio
16316
Diptheria
175885 1
Measles
503282 89
Role of vaccines and antibiotics

29. How does the future look?
15 classes of antibiotics
3 classes of antibiotics
BLEAK ; increase in drug-resistance /void in drug discovery

30. Normal microbiota and the host:
Locations of normal microbiota on and in the human body

31. Normal microbiota and the host:
Transient microbiota may be present for days, weeks, or months
Normal microbiota permanently colonize the host
Symbiosis is the relationship between normal microbiota and the host

32. Normal microbiota: how the host benefits ?
Microbial antagonism is competition between microbes.
Normal microbiota protect the host by:
occupying niches that pathogens might occupy
producing acids
producing bacteriocins
Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect.

33. Microbes Are invisible to the naked eye
Are everywhere around us, inside us, on us, in our food, in our homes, in the air we breathe and the water we wash in.
Are mostly useful, but some are harmful
Have been around for 3.8 bn years.

34. Microbes exist in huge numbers
In one single teaspoon of garden soil, there are over 100,000 microbes.
In 1ltr of seawater, there are over 1bn microbes.
On your skin there are more microbes than there are people in the world.
There are so many microbes, that scientists have only named <1% of them.
Microbes outnumber all other species and make up most of the living matter on the planet