This unit talks about man and his environment .Students are required to study within one week.

The World Health Organization (WHO) defines health as ‘a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity’.  They assert that physical and mental well-being is a human right, enabling a life without limitation or restriction. Physical health is about the body and mental health is about how people think and feel.

Hygiene refers to a series of practices performed to preserve health and prevent diseases, especially through cleanliness.

How to Ensure Good Personal Hygiene

Good personal hygiene habit includes:

  1. Washing the body often with sponge and soap.
  2. Cleaning the teeth at least twice a day.
  3. Washing the hair with soap or shampoo frequently.
  4. Washing hands with soap and running water after visiting the toilet.
  5. Washing hands with soap and running water before preparing and/ or eating food.
  6. Changing into clean clothes. Dirty clothes should be washed with soap before wearing them again.


Disease is a particular abnormal condition that affects the structure or function of an organism or any of its parts.

Classification of Diseases

Diseases can be classified into six groups:

  • Pathogenic diseases

These are diseases caused by other living organisms such as pathogens. Pathogens are disease causing organisms which are either microbes or parasites. Microbes include viruses, bacteria and fungi while parasites include protozoans, flatworms and roundworms etc. Diseases which are caused by pathogens are commonly referred to as infectious diseases.

  • Human-induced/ self-inflicted diseases

These are diseases linked with the way people live their life, either as individuals or collectively as a society. This is commonly caused by alcoholism, drug abuse and smoking as well as physical inactivity and unhealthy eating. Examples of such diseases include lung cancer, stroke, obesity and type II diabetes.

  • Deficiency diseases

These are diseases related to the absence of certain nutrients in the diet. These diseases include kwashiorkor, pellagra, scurvy, rickets etc.

  • Genetic and congenital disorders

An inherited medical condition caused by a chromosomal or DNA abnormality.

Examples include cystic fibrosis, Down’s syndrome, Turner’s syndrome, Klinefelter syndrome, sickle cell disease, haemophilia etc.

  • Ageing and degenerative diseases

Degeneration of the body tissues can also cause disease. For instance, weakening of the eye muscles can cause long-sightedness in many older people, and diseases of the circulatory system such as arteriosclerosis results from ageing. Ageing of the joint and bone tissues often leads to arthritis.

  • Mental illness

Mental illness covers a wide variety of disorders. Examples are schizophrenia, senile dementia and depression.

The six groups described above may also be grouped broadly into two categories namely infectious and non-infectious diseases.

Infectious diseases

Infectious diseases are diseases caused by pathogens such as bacteria, viruses, fungi and parasites and can be transmitted from one person to another. Many pathogens live in and on our bodies. They are normally harmless or even helpful, but under certain conditions, some may cause diseases. Most infectious diseases are communicable as they can spread from one person to another. Some are transmitted by bites from insects or animals. And others are acquired by ingesting contaminated food or water or being exposed to organisms in the environment.  Many of the diseases in group 1 (i.e. pathogenic diseases) are infectious diseases. Many infectious diseases, such as measles and chickenpox, can be prevented by vaccines. Frequent and thorough hand washing also offer protection from most infectious diseases.

Non-infectious diseases

Non-infectious diseases are not caused by pathogens and cannot be communicated from one person to another. Non-infectious diseases are mostly non-communicable as they cannot spread from one person to another. They may be caused by genetics factors or lifestyle choices. Group 2-6 diseases are non-infectious.


Examples of Communicable and Non-communicable diseases

As said earlier, communicable diseases can spread directly from person to person. The spread can happen through the air, through contact with contaminated surfaces, or through direct contact with blood, faeces, or other bodily fluids. Examples of communicable diseases include:

  1. Cholera
  2. Typhoid
  3. Measles
  4. Tuberculosis
  5. Hepatitis B
  6. Malaria
  7. Common cold
  8. Dysentery etc

Non-communicable diseases on the other hand are medical conditions that are not infectious and cannot be passed from one person to another. Examples include:

  1. Diabetes
  2. Stroke
  3. Cancer
  4. Asthma
  5. Cystic fibrosis
  6. Epilepsy
  7. Chronic kidney disease etc

Body Defence Mechanism

Skin– The skin acts as a protective wall to keep pathogens from entering into the body.  This wall includes the tiny hairs in the nose, the eyebrows and eyelashes.

Mucous Membranes– Mucous membranes produce mucus, a sticky fluid that traps pathogens.  These tissues line the mouth, nose, eyes, throat, and other parts of the body.

Sweat, Saliva, and Tears– These body fluids contain chemicals that kill bacteria.

Stomach Acid– Sometimes pathogens enter the body through the food we eat or the water we drink.  Most of the pathogens that enter the body in this way are killed by the hydrochloric acid in the stomach.

Phagocytic white blood cells– Ingestion of pathogenic microbes called phagocytosis are conducted by specialized cells such as monocyte/macrophage, neutrophils and natural killer cells.

Common Diseases of Humans


Malaria is a mosquito-borne infectious disease of humans and other animals caused by parasitic protozoan of the genus Plasmodium. Commonly, the disease is transmitted by a bite from infected female Anopheles mosquito. Malaria is common in tropical and subtropical regions because rainfall, warm temperatures and stagnant waters provide an environment ideal for mosquito larvae.

Causative organisms

Four species of Plasmodium can infect and be transmitted to humans. They are:

  • Plasmodium falciparum
  • Plasmodium vivax
  • Plasmodium ovale
  • Plasmodium malariae

The vast majority of deaths are caused by P. falciparum and P. vivax, while P. ovale and P. malariae cause a generally milder form of malaria that is rarely fatal.

Vector: Female Anopheles mosquitoes

Clinical signs and symptoms

The signs and symptoms of malaria typically begin 8-25 days following infection. The clinical presentations of the disease include:

  • Fever, shaking chills paroxysms (Fever pattern may be tertian or quartan)
  • Severe headache
  • Joint aches
  • Malaise
  • Fatigue
  • Nausea and vomiting
  • Muscular pains
  • Slight diarrhoea
  • Hemolytic anaemia


  • Microscopic examination of blood films (Thin smear or thick smear)
  • Rapid Diagnostic test
  • Molecular techniques (Polymerase Chain Reaction [PCR])


The most effective treatment for malaria infection is the use of Artemesinin Combination Therapy (ACT) which reduces resistance to any single drug component. These additional antimalarials include: amodiaquine, lumefanthrine, mefloquine etc.

Artemeter + Lumefanthrine

Artemeter + Amodiaquine

Artemeter + mefloquine

Control and prevention

  • Draining swamps and stagnant waters.
  • Destruction of the breeding sites of mosquitoes.
  • Using insecticide treated bed nets (ITNs) to prevent mosquito bites.
  • Using indoor residual spraying.
  • Vaccination (rts,s)


Tuberculosis or TB is a widespread, and in many cases fatal, infectious disease caused by various strains of mycobacteria, usually Mycobacteriumtuberculosis.

Mode of Transmission

It is spread through the air when people who have active TB infection cough, sneeze, sing, spit and expel infectious aerosol droplets.

Signs and symptoms

Tuberculosis may infect any part of the body, but most commonly occurs in the lungs (known as pulmonary tuberculosis). Extrapulmonary TB occurs when the disease develops outside of the lungs. Notable extrapulmonary infection sites include the pleura, the CNS, the lymphatic system, bones, joints etc

The classic symptoms of active TB infection are a prolonged cough with blood-tinged sputum, fever, chills, night sweats, loss of appetite, weight loss, fatigue, finger clubbing, chest pain.

Most infections do not have symptoms, known as latent tuberculosis. Latent infections eventually progresses to active disease which, if left untreated, kills more than 50% of those infected.


Diagnosis of active TB relies on radiography (commonly chest X-ray), PCR/DNA analysis, microscopic examination and microbiological culture of body fluids (sputum culture)

Diagnosis of latent TB relies on the tuberculin skin test (TST)


Treatment of tuberculosis is difficult and requires administration of multiple antibiotics over a long period of time. Some of these antibiotics are:

  • isoniazid and rifampicin
  • rifampicin, isoniazid, pyrazinamide and ethambutol

Prevention and control

Prevention relies on screening programmesandvaccination with the Bacillus Calmette – Guerin vaccine.

Common cold

The common cold (also known as head cold or simply a cold) is a viral infectious disease of the upper respiratory tract which primarily affects the nose.


Over 200 virus strains are implicated in the cause of the common cold. The most commonly implicated virus is the rhinovirus.

Signs and symptoms

The typical symptoms of a common cold include cough, runny nose, nasal congestion and sore throat, sometimes accompanied by muscle ache, fatigue, headache and loss of appetite.

Mode of transmission

The disease is typically transmitted through airborne droplets (aerosols), direct contact with infected nasal secretions, or formites (contaminated objects).


The common cold disease is frequently defined as nasal inflammation with varying amount of throat inflammation. Self-diagnosis is frequent. Isolation of the actual viral agent involved is rarely performed, and it is generally not possible to identify the virus type through symptoms.


Physical measures such as regular hand washing and wearing face masks is effective in reducing the transmission of common cold viruses. Isolation, example quarantine, is not possible as the disease is so widespread and symptoms are non-specific. Vaccination has proved difficult as there are so many viruses involved and they mutate rapidly.


No medications or herbal remedies have been conclusively demonstrated to shorten the duration of infection. Treatment comprises symptomatic relief. Getting plenty of rest, drinking fluids to maintain hydration and gargling with warm salt water are reasonable conservative measures.


Hepatitis is a medical condition defined by the inflammation of the liver. The condition can be self-limiting (healing on its own) or can progress to fibrosis (scarring) and cirrhosis. Hepatitis may occur with limited or no symptoms, but often leads to jaundice, poor appetite and malaise. The condition may be acute (when it last less than six months) or chronic (when it persist longer).


Viral hepatitis is the most common form worldwide caused by five unrelated viruses namely hepatitis A, hepatitis B (the most common), hepatitis C, hepatitis D and hepatitis E.

Non-viral hepatitis is caused by toxic substances (notably alcohol, certain medications, certain industrial organic solvents) and autoimmune diseases.

Signs and symptoms

Acute form of the condition is characterized by malaise, muscle and joint aches, fever, nausea (or vomiting), diarrhea and headache.

Chronic hepatitis may cause nonspecific symptoms such as malaise, tiredness and weakness, and often lead to no symptoms at all. The presence of jaundice indicates advance liver damage.


Diagnosis is made by assessing an individual’s symptoms, physical examination and medical history in conjunction with blood tests, liver biopsy, and imaging.


Vaccines are available to prevent hepatitis A and B.


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