Koch's Postulates, Immunity, Antibiotics, Antivirals & Epidemics

Koch's Postulates

Koch repeated his experiments with other diseases such as cholera and tuberculosis. The central idea was that each disease is caused by a specific microorganism and that each organism produces a distinct disease.

Antigens, Antibodies and Immune Response

Molecular bodies or antigens are recognized by our immune system and stimulate an immune response.

Antibodies are proteins produced by white blood cells that circulate in the blood.

The immune response features:

• Diversity
• Specificity
• Distinction between self and non‑self
• Immunological memory

Antibiotics and Differences

Antibiotics are substances of chemical, biological, or synthetic origin that kill bacteria or prevent their growth and multiplication. Their discovery was a revolution in the fight against infectious diseases. Natural molecules with similar effects to synthetic antibiotics also exist.

Antivirals

Antivirals act on viruses and have no effect on other infectious agents such as bacteria, fungi, or protozoa. For bacterial infections, other drugs should be used. The importance of certain viral diseases, such as AIDS, has driven pharmaceutical companies to invest in antiviral development.

White Blood Cells

Not all blood cells are white cells. White blood cells (leukocytes) have nuclei and can leave the bloodstream to enter tissues and respond to infection.

Phagocytes engulf foreign bodies such as bacteria; macrophages are a major phagocytic cell type.

Lymphocytes

Lymphocytes are a major class of white blood cells. B lymphocytes produce antibodies, while T lymphocytes destroy virus‑infected cells.

Influenza Virus

1. The virus adheres to the cell membrane through recognition between viral surface molecules and membrane receptors.
2. The virus enters the cell by endocytosis.
3. Once inside the cell, the viral particle escapes the vesicle membrane, releasing fragments of RNA.
4. The host cell machinery replicates copies of the viral genetic information.
5. New viruses bud from the cell surrounded by a membranous envelope that can infect new cells.

Prevention of Bioterrorism

Viruses and bacteria can be transformed into weapons in the hands of terrorists. In the days following the 11 September 2001 attacks, the threat of infectious attacks prompted many countries to develop prevention plans, ranging from enhanced laboratory surveillance to public health preparedness.

Any risk of a massive attack is limited by the difficulty and cost of manufacturing and transporting pathogenic microorganisms at scale.

Diseases of the 21st Century

Diseases that had been almost forgotten have resurfaced. Contributing factors include rapid population growth, large urban concentrations, and increased human mobility, all of which facilitate the spread of infectious agents. Changes in land and water use also influence the emergence and reemergence of diseases. Responding to recent epidemics requires international solidarity and mobilization.