1. Modern Science vs. Infectious Disease

2. Modern Medicine
Although modern medicine has its roots in the early modern period, it was not really until the last third of the 19th century that an understanding of infectious disease could be grounded in empirical proof
From that time to the second half of the 20th century there was a growing optimism that modern medical science could eradicate infectious disease with vaccines and later antibiotics
Since the 1970s, however, that confidence has been shattered with the spread of new pathogens, and mutations that are resistant to vaccines and antibiotics

3. Smallpox inoculation
The practice of inoculation for smallpox is ancient, practiced in India and China
The simple idea behind it is to expose a person with no immunity to smallpox to material from a smallpox pustule directly into the skin; this produces a less severe infection than naturally acquired smallpox, but still offers the immunity to it
The practice was introduced into Europe in the eighteenth century by Lady Mary Wortley Montagu, who had learned about the procedure in Istanbul while accompanying her husband as British Ambassador to the Ottoman Empire in 1718

4. Lady Mary Wortley Montagu
In 1721, having returned to England, a smallpox epidemic was breaking out and she asked her physician to inoculate her children
Because she was one of society’s elites, she was able to interest many other aristocrats in the practice of inoculation, including the royal family
Because of this elite support, the practice became widely known and practiced, both in Britain and in the colonies
This process was known as the arm-to-arm process, because a live infected person was needed in order to administer the inoculation

5. The development of cowpox vaccine
There were dangers, however, in inoculation; some people could die from being exposed to the disease
One English country doctor, Edward Jenner, noticed in that people who had suffered from cowpox were also immune to smallpox
Cowpox was a disease that affected the udders of cows, and was commonly transferred to the hands of milkmaids
Jenner transferred the matter from a cowpox lesion under a young boys skin, who contracted a mild form of the disease; a couple of months later he inoculated the child, who did not get ill from the smallpox virus
Cowpox lesions on a dairymaid’s hands

6. Edward Jenner performing a vaccination using cowpox in 1796

7. Jenner published his findings in 1798
He coined the term ‘vaccination’ which he borrowed from the Latin word for cow – vacca
Within one or two years, doctors from across Europe and America were following the procedure

8. Not everybody immediately agreed with vaccination; this satirical drawing by James Gilray in 1802 illustrates the popular conception that cowpox vaccination could give people cow-like features

9. Germ theory of disease
Even with the growing use of vaccination, there was still a major dispute in the medical science community about the cause of the spread and transmission of infectious disease in the nineteenth century
In many scientific circles the Miasma theory – where diseases were spread through contaminated air -- continued to dominate and the idea that microscopic germs were the cause were considered too crazy to be true
Several scientists in the nineteenth century proposed germs theories of infectious diseases, but could not gain the same currency

10. Louis Pasteur ( )
One of the breakthrough scientists in the field was the French microbiologist Louis Pasteur
His experiments with bacteria led to breakthroughs in the application of germ theory to clinical medicine
He showed in his experiments that microorganisms were responsible for spoiling beverages, and developed the method of heating beverages to remove bacteria (pasteurization)

11. Robert Koch ( )
A German physician and researcher whose main contribution was to use the microscope as a tool to see microorganisms – thus allowing him to isolate and grow them – and to show that a specific microorganism is the specific cause of a disease
His research led him to find the causative microorganisms for anthrax, cholera, and tuberculosis

12. Koch’s postulates
1. The organism must always be present, in every case of the disease.
2. The organism must be isolated from a host containing the disease and grown in pure culture.
3. Samples of the organism taken from pure culture must cause the same disease when inoculated into a healthy, susceptible animal in the laboratory.
4. The organism must be isolated from the inoculated animal and must be identified as the same original organism first isolated from the originally diseased host.

13. Golden age of microbiology (1860-1910)
Building on the advances made by Pasteur and Koch, a new generation of bacteriologists set to work on finding the causative agents for all of the known infectious diseases
By the end of this period there was almost unanimous agreement among scientists about the germ theory of disease, and several other theories like Miasma (bad air) and ”spontaneous contamination” were rejected almost overnight, putting the study of disease, and of disease prevention on a new footing
Building on the rapid advances in microbiology opened the door for other types of research to combat infectious diseases

14. The development of antibiotics
The German physician and scientist Paul Ehrlich ( ) was one of the first people to conceive of creating a drug that could combat a particular microorganism without harming other cells – which he called a ”magic bullet”
This put other scientists on the quest to discover or produce chemicals that inhibit the growth of bacteria in order to treat bacterial infections
Ehrlich coined the term ‘chemotherapy’ – the use of chemicals to treat a disease and discovers an important antibiotic -- Salvarsan

15. Alexander Fleming ( )
In 1928 Fleming, a Scot, discovered the antibiotic substance benzypenicillin (Penicillin G) from mould – marking the beginning of modern antibiotics
The discovery of penicillin – a broad spectrum antibiotic (i.e. it can neutralize several bacteria) – was one step ... Over the next decade or so the challenge was to be able to mass produce it
Fleming was cautious about the use of penicillin, especially in the correct dosage

16. Wars in the 20th Century
The world wars of the 20th century, and other conflicts gave ample opportunity for medical research and a pressing need for the development of cures to deal with infectious diseases that are associated with warfare
World War II especially gave new impetus for the discovery of antibiotics to deal with the thousands of wounded soldiers and civilians
As we have seen, historically warfare and infectious disease went hand in hand; WWII was the first war where combatant nations had the ability to prevent mass epidemics among soldiers and civilians

17. Antimicrobial resistance
Despite the great discoveries of new antibiotics in the post-WWII period, or perhaps because of it, it was found that some microbes developed resistance to antibiotics – so-called superbugs
Antimicrobial resistance grows over time (as the microbes evolve) through genetic change; thus the drugs that were so effective in the 1950s are no longer as effective
One of the main reasons for the rise in antimicrobial resistance is the overuse or misuse of antibiotics (i.e. they do not work on viruses)
Scientists are predicting that we are currently in the midst of an emerging crisis as a result of of the growth of antimicrobial resistance

18. New pathogens
Just as older pathogens are changing and modifying to resist human efforts to kill them, so new pathogens are making their way into the human world
HIV-AIDS, SARS and Ebola are examples of pathogens that have recently made the leap from animals to humans, and have a deadly force to them
This makes some critics question whether we have not become too comfortable with the idea that science can stay ahead of microbes, especially since microbes have the upper hand in the relationship between pathogen and host

19. A look ahead
On Tuesday we will discuss the final exam. I will provide you with some sample questions and offer you some ideas and strategies for studying for the exam
On Thursday I shall offer some final thoughts to tie the course material together and there will be time for questions about the final exam