Infectious Diseases - Timeline

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  • Infectious Diseases: Timeline
  • Edward Jenner and vaccination
  • Ignaz Semmelweiss and the spread of infection
  • Louis Pasteur and the germ theory of disease
  • Joseph Lister and antiseptic surgery
  • Alexander Fleming and the discovery of penicillin
  • Recent Events
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Louis Pasteur and the germ theory of disease

The work of people like Jenner and Semmelweiss led doctors and scientists to think that perhaps infectious diseases were caused by an infectious agent or 'germ'. This was the germ theory of disease. It took a very long time for this idea to be accepted. Much of the work that led to a wide acceptance of the germ theory is down to Louis Pasteur, helped by the development of microscope techniques by people such as Robert Koch which made microorganisms visible and identifiable. Pasteur made a number of important steps forward.

  • He showed that fermentation is the result of the action of microorganisms on sugar
  • Many people at the time believed that living things could arise from non-living things by the action of God – a theory known as spontaneous generation. Pasteur was convinced that any growths that appeared, such as mould on food as it goes bad, were from microscopic organisms already present in the air.

    First Pasteur showed that the results of his main rival were dubious. Then he showed that if he boiled broth and immediately sealed the container it would stay clear. But once he added material which had been exposed to the air, microorganisms grew in the broth and it turned cloudy. Finally he designed a series of experiments using swan necked flasks which showed once and for all that any microorganisms which appear in boiled broth come from the air.

  • In 1845-6 a mystery disease wiped out silkworms around the world, Pasteur showed that the disease was caused by microorganisms which were only found in the tissues of diseased silkworms, moths and eggs. They could be seen using a microscope. He found a way of avoiding the disease by identifying the infected eggs, saving the silk industry. This was the first clear evidence of microorganisms causing disease.
  • Three of Pasteur's daughters died of infectious diseases. He did a lot of work on these diseases, confirming that they were caused by germs (microorganisms) and developed vaccines against a number of these diseases. His work influenced Joseph Lister , who wrote and thanked him for his help.


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Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.
Protein that is produced by lymphocytes (white blood cells) and that attaches to a specific antigen.
Molecule on the surface of a pathogen that identifies it as a foreign invader to the immune system.
Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus.
The use of biological organisms or enzymes to create, break down or transform a material
To cut apart, or separate, tissue especially for anatomical study.
Exponential growth
If something is growing exponentially the larger the quantity gets, the faster it grows
Micro-organism that can grow in long tubes called hyphae or as single cells. Fungi have a nucleus, cytoplasm and a cell wall.
Herd immunity
If a high percentage of a population is immune to a disease the disease cannot be passed on because it cannot find new hosts.
Infection caused by the human immunodeficiency virus (HIV). It attacks and destroys the immune system.
Hybridoma cells are formed by fusing a specific antibody-producing cell with a type of cancer cell that grows well in tissue culture
Immune system
The body's natural defence mechanism against infectious diseases.
A process which gives immune resistance to a particular disease. The human or animal is exposed to a harmless antigen in order to raise antibodies and provide an immune memory.
A type of white blood cell that make antibodies to fight off infections.
A type of white blood cell that consumes dead pathogens that have been killed by antibodies.
Organism that feeds off another living host and causes it some damage. An example of a parasite is a tapeworm that lives in the digestive system of a host organism.
A micro-organism that causes disease.
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.
Protozoa are one-celled animals
A spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavourable conditions.
A poisonous or toxic substance - produced by pathogens.
A small amount of dead or weakened pathogen is introduced into the body. It prepares the immune system to prevent future infections with the live pathogen.
Medicine that contains a dead or weakened pathogen. It stimulates the immune system so that the vaccinated person has an immunity against that particular disease.
The smallest of living organisms. Viruses are made up of a ball of protein that contains a small amount of the virus DNA. They can only reproduce after they have infected a host cell.
World Health Organization.
Chlorinated Lime
A mixture of calcium hydroxide, calcium chloride and calcium hypochlorite.
Free of pathogens. An aseptic technique is one performed under sterile conditions.
A chemical which can destroy microorganisms. Antiseptics are applied to the surface of the skin or to living tissue to reduce the possibility of infection.