Why do we fall ill?

AIDS (Acquired Immunodeficiency Syndrome) weakens the immune system by destroying CD4 cells, making the body vulnerable to opportunistic infections. Patients typically die from these secondary infections (pneumonia, tuberculosis, etc.) rather than the HIV virus itself.

Smallpox is the only human disease to have been completely eradicated from the world through a successful global vaccination campaign led by WHO, with the last natural case occurring in 1977. Tetanus remains a threat through soil contamination, rabies still exists in animal populations, and polio continues to circulate in a few countries.

Japanese encephalitis is a viral brain infection transmitted by mosquitoes, often colloquially called 'brain fever' due to the inflammation and swelling of brain tissue it causes. Diabetes is a metabolic disorder, diarrhoea is a gastrointestinal condition, and malaria is a blood infection affecting different systems entirely.

Hepatitis specifically causes inflammation of the liver, whether from viral infection (Hepatitis A, B, C), alcohol, toxins, or autoimmune conditions. Kala-azar primarily affects the spleen and liver but is a parasitic disease called visceral leishmaniasis, SARS is a respiratory illness, and amoebiasis mainly infects the intestines.

When microbes enter through the nose, they travel down the respiratory tract and primarily infect the lungs and respiratory system. The heart is vascular and not directly accessible this way, while the gut requires swallowing through the mouth, and the liver would require bloodstream circulation from the lungs.

This describes the principle of immunization, where memory immune cells recognize pathogens from previous exposure and mount a stronger, faster response. Infection refers to the initial invasion, prevention is stopping disease before it occurs, and disease spread refers to transmission between people.

Diarrhoea is fundamentally a gastrointestinal disorder involving frequent loose or watery bowel movements, typically caused by infections, toxins, or malabsorption in the digestive tract. It does not involve the brain, lungs, or kidneys as primary affected organs.

Brain fever (Japanese encephalitis) is caused by a flavivirus transmitted by mosquitoes, not by bacteria, protozoa, or fungi. The virus directly infects and inflames brain tissue, causing the characteristic symptoms of encephalitis.

Destroying mosquito breeding sites (standing water) is a key public health strategy because it eliminates where mosquitoes lay eggs and larvae develop. Feeding places, spreading areas, and flying routes are not targeted for destruction since the goal is preventing reproduction.

Childhood immunization programs administer vaccines, which contain weakened or inactivated pathogens to stimulate protective immune responses without causing disease. Medicines treat existing conditions, narcotics are controlled substances, and antibiotics kill bacteria but do not prevent viral infections.

Headache, vomiting, and unconsciousness are classic symptoms of brain involvement because increased intracranial pressure or inflammation affects consciousness centers. While lungs and liver problems can cause nausea, and kidney issues can cause headaches, this specific symptom cluster strongly indicates brain pathology.

A handkerchief catches respiratory droplets when sneezing, preventing germs from spreading to others. Soap is for washing hands, your hand alone doesn't trap droplets, and a pillow is not a practical sneeze-catchting tool in public.

Rabies virus is transmitted through the saliva of infected animals, typically entering the body through a bite wound. It does not spread through accidents, sexual contact, or casual physical touching.

Japanese encephalitis virus is a flavivirus that specifically infects the brain, causing inflammation (encephalitis means brain inflammation). It does not primarily target the heart, liver, or kidneys.

HIV (Human Immunodeficiency Virus) specifically attacks and destroys cells of the immune system, particularly CD4 T-cells, weakening the body's ability to fight infections. It does not directly damage the nervous, respiratory, or muscular systems as its primary target.

Jaundice occurs when the liver cannot properly process bilirubin (a breakdown product of red blood cells), causing yellowing of skin and eyes. While other organs may be affected in various diseases, jaundice specifically indicates liver dysfunction.

Diarrhea is characterized by frequent loose or watery bowel movements, leading to excessive fluid loss and dehydration. Malaria is caused by a parasite spread by mosquitoes, tuberculosis is a bacterial lung infection, and tetanus is a nervous system infection - none primarily cause dehydration through loose motions.

When you have a cold or cough, you should avoid crowded places to prevent spreading germs and use a handkerchief when sneezing to trap droplets. Childhood immunization helps prevent diseases but isn't a direct cold/cough precaution, and preventing mosquito breeding is for malaria/dengue, not respiratory illnesses.

Inflammation is the immune system's response where various cells (white blood cells, etc.) are recruited to the site of infection or injury to fight pathogens and begin healing. Infection is the pathogen's invasion, immunization is preventive exposure, and vaccination is a preventive method - none describe the cellular recruitment process.

A solution of clean boiled water with sugar and salt describes Oral Rehydration Solution (ORS), used to replace lost fluids and electrolytes during gastrointestinal disorders like diarrhea and vomiting. It is not a treatment for brain, kidney, or liver disorders.

After a road accident injury, anti-tetanus injection (tetanus toxoid) is given to prevent tetanus infection, which can enter through wounds contaminated with soil or dirt. Anti-malarial is for parasite prevention, anti-rabies is for animal bites, and anti-diarrhea injections are not standard treatments.

Hepatitis viruses (A, B, C, D, E) cause inflammation of the liver, which leads to jaundice as a primary symptom due to impaired bilirubin processing. Syphilis is caused by bacteria, AIDS by HIV, and tuberculosis by Mycobacterium - none are hepatitis-related.

Gastrointestinal disorders are treated with oral medications (drugs), antibiotics for bacterial infections, and Oral Rehydration Solution (ORS) for dehydration. Antiseptics like Dettol or tincture are used for external wound disinfection and are not given internally for GI problems.

Cough and breathlessness are respiratory symptoms because they affect the lungs and airways. Lung infections like pneumonia or bronchitis directly cause these symptoms as the respiratory system struggles to function properly. The brain, liver, and kidneys are not involved in breathing or coughing reflexes.

Tuberculosis is caused by Mycobacterium tuberculosis, which primarily infects the lungs. While TB can affect other organs (extrapulmonary TB), the lungs are the most common and primary site of infection when the bacteria enter the body. The gut, heart, and brain are not the typical entry points or primary targets.

Vaccines contain weakened or killed pathogens (or their parts) to stimulate immunity without causing disease. They are preventive tools that stop infections rather than spread them. The other options (vectors, contact, air) are all valid transmission routes for infectious agents.

Malaria is caused by Plasmodium parasites transmitted through the bite of infected female Anopheles mosquitoes. Tetanus comes from Clostridium bacteria in soil, diarrhea from contaminated water/food, and ascariasis from roundworm eggs in soil - none are mosquito-borne.

DDT (Dichloro-Diphenyl-Trichloroethane) is a synthetic insecticide widely used to control adult mosquitoes. BCG and DPT are vaccines for tuberculosis and diphtheria-pertussis-tetanus respectively, while ATS is an antitoxin used for tetanus treatment - none kill mosquitoes.

The immune system identifies and destroys pathogens before infections become severe. When immune function is compromised, even minor gut infections can progress to serious conditions like dysentery with bloody diarrhea, as the body cannot control the infection. The circulatory, respiratory, and nervous systems are not primarily responsible for fighting infections.

Oral-rehydration therapy (ORT) is a treatment for dehydration caused by diarrheal diseases like cholera or rotavirus, not a malaria prevention method. Malaria prevention involves stopping mosquito bites through nets, insecticides, and eliminating breeding sites - none of which ORT addresses.

The common cold virus spreads through multiple routes: airborne droplets when coughing/sneezing (air/water), touching contaminated surfaces like towels or utensils (fomites), and direct contact like handshakes. Since all listed methods are valid transmission routes, "All of the above" is correct.

Viruses replicate inside host cells using the host's own machinery, making it extremely difficult to develop drugs that target the virus without harming human cells. Bacteria, fungi, and protozoa have their own cellular structures and metabolic pathways that can be selectively targeted with fewer side effects.

Immunization (vaccination) introduces weakened or killed pathogens to stimulate immune memory, preventing future infections. Medicines treat active diseases, tonics are general health supplements, and while pure water prevents some water-borne diseases, immunization is the specific medical prevention method listed.

Quinine, Chloroquine, and Primaquine are well-established anti-malarial drugs used to treat or prevent malaria. "Antiquine" appears to be a fictional or misspelled drug name with no pharmaceutical validity - it doesn't exist as an anti-malarial medication.

The immune system is the body's defense network that identifies and destroys disease-causing microbes through white blood cells, antibodies, and other defense mechanisms. The nervous system transmits signals, the respiratory system handles gas exchange, and the muscular system enables movement - none directly fight pathogens.

Vaccines work by priming the immune system to recognize and fight specific pathogens before actual infection occurs. They are preventive tools, not treatments for diseases that have already developed.

Hepatitis-A is primarily transmitted through the fecal-oral route, often via contaminated water or food in areas with poor sanitation. In India, where waterborne diseases are common, children frequently get exposed through unsafe drinking water.

Trypanosoma is responsible for sleeping sickness.