Human health and diseases

• Biology is the youngest of the formalised disciplines of natural science. Progress in physics and chemistry proceeded much faster than in Biology. Applications of physics and chemistry in our daily life also have a higher visibility than those of biology.
• Twentieth century and certainly twenty-first century has demonstrated the utility of biological knowledge in furthering human welfare, be it in health sector or agriculture.
• The discovery of antibiotics, and synthetic plant-derived drugs, anaesthetics have changed medical practice on one hand and human health on the other hand. Life expectancy of human beings have dramatically changed over the years.
• Agricultural practices, food processing and diagnostics have brought socio-cultural changes in human communities.
• M.S. Swaminathan


  Born in August 1925 in Kumbakonam in Tamil Nadu, did his graduation and post-graduation in Botany from Madras University, worked in different capacities in large number of institutions in India and abroad and developed his expertise in genetics and plant breeding.
• M.S. Swaminathan

  • Established the School of Cytogenetics and Radiation Research at the Indian Agricultural Research Institute (IARI), developed short-duration high-yielding varieties of rice including scented Basmati, developed the concept of crop cafeteria, crop scheduling and genetically improving the yield and quality, initiated collaboration with Norman Borlaug which culminated in the 'Green Revolution' through introduction of Mexican varieties of wheat in India, initiated 'Lab-to-Land', food security and several other environmental programmes, honoured with Padma Bhushan and several other prestigious awards, medals and fellowships by institutions of excellence.
• Health

  A state of complete physical, mental and social well-being, not just the absence of disease or physical fitness
• Balanced diet, personal hygiene and regular exercise are very important to maintain good health. Yoga has been practised since time immemorial to achieve physical and mental health.
• Awareness about diseases and their effect on different bodily functions, vaccination (immunisation) against infectious diseases, proper disposal of wastes, control of vectors and maintenance of hygienic food and water resources are necessary for achieving good health.
• Disease

  When the functioning of one or more organs or systems of the body is adversely affected, characterised by various signs and symptoms
• Types of diseases

  • Infectious
  • Non-infectious
• Infectious diseases


  Diseases which are easily transmitted from one person to another
• Non-infectious diseases


  Diseases which are not easily transmitted from one person to another, including cancer
• Pathogens

  Disease-causing organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc.
• Pathogens

  • They have to adapt to life within the environment of the host, e.g. pathogens that enter the gut must survive in the stomach at low pH and resist digestive enzymes
• Typhoid fever

  Caused by the pathogenic bacterium Salmonella typhi, symptoms include sustained high fever, weakness, stomach pain, constipation, headache and loss of appetite
• Typhoid fever could be confirmed by Widal test.
• Mary Mallon, nicknamed Typhoid Mary, was a typhoid carrier who continued to spread typhoid for several years through the food she prepared.
• Pneumonia

  Caused by bacteria like Streptococcus pneumoniae and Haemophilus influenzae, infects the alveoli (air filled sacs) of the lungs, symptoms include fever, chills, cough and headache
• Common cold

  Caused by rhino viruses, infects the nose and respiratory passage but not the lungs, symptoms include nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness
• Malaria


  Caused by different species of the protozoan Plasmodium, transmitted by the bite of infected female Anopheles mosquito, symptoms include recurring chills and high fever
• Amoebiasis (amoebic dysentery)


  Caused by the protozoan parasite Entamoeba histolytica in the large intestine, symptoms include constipation, abdominal pain and cramps, stools with excess mucous and blood clots
• Ascariasis


  Caused by the common roundworm Ascaris, symptoms include internal bleeding, muscular pain, fever, anemia and blockage of the intestinal passage
• Filariasis (elephantiasis)

  Caused by the filarial worms Wuchereria bancrofti and Wuchereria malayi, transmitted by female mosquito vectors, results in chronic inflammation and gross deformities of the lower limbs and genital organs
• Ringworm

  Caused by fungi of the genera Microsporum, Trichophyton and Epidermophyton, symptoms include dry, scaly lesions on skin, nails and scalp accompanied by intense itching
• Measures for prevention and control of infectious diseases

  • Maintaining personal hygiene (keeping body clean, consuming clean food and water)
  • Maintaining public hygiene (proper disposal of waste and excreta, disinfection of water sources)
  • Avoiding close contact with infected persons or their belongings
  • Controlling or eliminating insect vectors and their breeding places
• Advancements in biological science have enabled effective dealing with many infectious diseases through the use of vaccines and immunisation programmes, including the complete eradication of smallpox.
• Controlling or eliminating insect vectors and their breeding places

  1. Avoiding stagnation of water in and around residential areas

  2. Regular cleaning of household coolers

  3. Use of mosquito nets

  4. Introducing fishes like Gambusia in ponds that feed on mosquito larvae

  5. Spraying of insecticides in ditches, drainage areas and swamps
• Preventing entry of mosquitoes

  Providing doors and windows with wire mesh
• Precautions against vector-borne diseases like dengue and chikungunya have become more important in light of recent widespread incidences in many parts of India
• Advancements in biological science

  • Enabled us to effectively deal with many infectious diseases
• Eradicating and controlling infectious diseases

  1. Use of vaccines and immunisation programmes

  2. Discovery of antibiotics and various other drugs
• Immunity


  The overall ability of the host to fight disease-causing organisms
• Types of immunity

  • Innate immunity
  • Acquired immunity
• Innate immunity


  • Non-specific type of defence, present at the time of birth
  • Provides different types of barriers to the entry of foreign agents into the body
• Barriers in innate immunity

  • Physical barriers
  • Physiological barriers
  • Cellular barriers
  • Cytokine barriers
• Acquired immunity


  • Pathogen specific
  • Characterised by memory
• Primary and secondary immune responses

  1. Primary response is of low intensity

  2. Secondary/anamnestic response is highly intensified
• 1. lymphocytes


  Produce antibodies in response to pathogens
• 1. lymphocytes


  Help B cells produce antibodies, but do not secrete antibodies themselves