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Diseases: Cause and Control

Health is a condition of complete physical, mental, and social well-being. On the other hand, a disease refers to a situation where the body's vital functions are disrupted, either physiologically or psychologically.

Categories of Diseases

• Endemic Disease: A disease is considered endemic when it is confined to a specific area and affects a small number of people. Examples include yellow fever and goitre.
• Epidemic Disease: An epidemic disease spreads from one place to another, leading to an outbreak that affects a large population simultaneously. An example of this is the plague.
• Pandemic Disease: When a disease occurs worldwide, it is classified as a pandemic disease. AIDS is an example of a pandemic disease.
• Sporadic Disease: A sporadic disease occurs in single, scattered cases. Examples include malaria and cholera.
• Communicable or Infectious Diseases: These diseases are caused by infectious agents or pathogens and can spread from one person to another. Examples include tuberculosis, chickenpox, and measles.
• Non-communicable or Noninfectious Diseases: These diseases do not spread from one person to another. Examples include beriberi, scurvy, and arthritis.
• Bacterial Diseases: Diseases caused by bacteria are known as bacterial diseases. Examples include cholera, tetanus, and syphilis.
• Viral Diseases: Diseases caused by viruses are referred to as viral diseases. Examples include poliomyelitis, mumps, and rabies.
• Protozoal Diseases: Diseases caused by protozoa are called protozoal diseases. Examples include malaria and amoebic dysentery.
• Parasitic Diseases: Diseases caused by parasitic worms are known as parasitic diseases. Examples include ascariasis and taeniasis.
• Food-borne Diseases: These diseases are caused by consuming food contaminated with chemical toxins or pathogens. Examples include taeniasis and trichinosis.
• Water-borne Diseases: Diseases caused by consuming contaminated water are called water-borne diseases. Examples include typhoid fever, cholera, and hepatitis A.
• Air-borne Diseases: These diseases spread through the air when droplets of pathogens are expelled due to coughing, sneezing, or talking. Examples include influenza and meningitis.
• Insect-borne Diseases: Diseases caused by pathogens transmitted by insects and ticks are known as insect-borne diseases. Examples include malaria and elephantiasis.

Diseases Caused by Bacteria

Diseases Caused by Bacteria

Leprosy (Mycobacterium leprae)

• Incubation Period: Several years
• Mode of Transmission: Contact, highly contagious
• Symptoms: Nervous loss of sensation, paralysis, and deformity
• Prevention: Vaccination
• Other Measures: Good nutrition and sanitation

Gonorrhea (Neisseria gonorrhoeae)

• Incubation Period: 3–10 days
• Mode of Transmission: Sexual contact
• Symptoms: Pain during urination, pus-like discharge in genital tubes

Diseases Caused by Protozoa

Malaria (Plasmodium falciparum)

• Incubation Period: About 3 weeks
• Mode of Transmission: Female Anopheles mosquito acts as a carrier
• Symptoms: Cold Stage: Sudden onset of fever Hot Stage: Body temperature may rise to 41°C (106°F) Sweating Stage: Profuse sweating and lowering of body temperature
• Prevention: Reduction or elimination of mosquito populations, prevention of mosquito bites using nets and repellents, drinking water boiled with neem leaves and inflorescence

Amoebic Dysentery or Amoebiasis (Entamoeba histolytica)

• Incubation Period: About 1 week
• Mode of Transmission: Food and water contaminated by flies, faeces of an infected person
• Symptoms: Diarrhoea or watery motions containing mucus or blood, abdominal pain, destruction of intestinal lining, constipation alternating with diarrhoea, stomach convulsions
• Prevention: Keeping food covered to avoid fly contamination, controlling fly populations, using clean, boiled, and cooled water for drinking, avoiding spicy and fried foods

Sleeping Sickness (Trypanosomiasis)

• Incubation Period: From 3 days to 3 weeks
• Mode of Transmission: Bite of the Tsetse fly
• Symptoms: Swollen, red, painful nodule at the site of the fly bite, fever, headache, itchiness, joint pain in the first phase, mood changes, anxiety, insomnia in the later phase
• Prevention and Treatment: Insect control measures, administration of drugs such as melarsoprol, pentamidine, and suramin

Diseases Caused by Parasitic Worms

Ascariasis (Ascaris lumbricoides)

• Incubation Period: About 4–8 weeks
• Mode of Transmission: Soil, food, and water contaminated with eggs of the female worm; flies act as carriers
• Symptoms: Bleeding in liver, heart, lungs, sudden contraction of muscles, fever, and anaemia
• Prevention: Maintenance of personal hygiene, using boiled, cooled, and fresh water for drinking

Taeniasis (Taenia solium)

• Incubation Period: About 8–14 weeks
• Mode of Transmission: Consumption of infected pork and beef
• Symptoms: Extreme weakness
• Prevention: Avoiding raw meat, cooking meat at a temperature greater than 140°F for about 5 minutes, freezing meat

Filariasis/Elephantiasis (Filarial worm Wuchereria bancrofti)

• Incubation Period: 4 weeks to 1 year
• Mode of Transmission: Bite of the Culex mosquito
• Symptoms: Characteristic swelling in the arms, legs, and chest, swollen legs resembling those of an elephant, inflammation of lymph glands and lymph vessels, enlargement of limbs/ankle, fever with chills
• Prevention and Treatment: Avoiding mosquito bites, eradication of the vector, use of antibiotics and anti-inflammatory analgesics

Differences between Viruses and Bacteria

Common Viral Diseases

Poliomyelitis (Polio virus)

• Incubation Period: 7–14 days
• Mode of Transmission: Excreta or secretion of the nose; incubates in the intestine, passes to the brain through the blood vessels
• Symptoms: Muscle paralysis of legs, common cold, sore throat, fever, fatigue, headache, vomiting, and reddening of the throat
• Prevention: Vaccination, polio vaccine

Mumps (Myxovirus parotitis)

• Incubation Period: 12–26 days
• Mode of Transmission: Contact, contaminated food or milk and air
• Symptoms: Characteristic painful swelling of salivary glands, pain while opening the mouth, earache, headache, and fever
• Prevention: Vaccination of gamma globulin, complete isolation

Rabies (Rhabdovirus)

• Incubation Period: 30 days or more
• Mode of Transmission: Mad dog bite (canine disease)

Infectious Diseases and their Prevention

A disease that is caused by the infection of pathogen like bacteria, virus, fungi, parasites or prions is known as infectious disease. Infectious diseases can be spread from one person to another through air, water, food, physical contact, or other means. In this chapter, we will discuss some major infectious diseases, their symptoms, and preventive measures.