Answer 1: Arun most likely has an infectious disease. Reason: fever that responds temporarily to medicine but returns suggests an infection (caused by microbes) rather than a chronic non-infectious condition. Infectious diseases often present with fever, body ache and can be self-limiting or require specific treatment.

Answer 2: Two steps the school should take: (a) Isolate Arun from other students until diagnosed and recovered; (b) Encourage hand hygiene and sanitize commonly touched surfaces; inform parents and recommend medical check-up.

Answer 1: The likely modes are droplet transmission (sneezing/coughing) and fomite transmission through contaminated utensils or surfaces. Close contact facilitates spread of respiratory viruses.

Answer 2: Preventive measures: (a) Avoid sharing utensils, towels and encourage covering mouth while coughing/sneezing; (b) Regular handwashing with soap, and disinfecting surfaces.

Answer 1: Meera shows acquired (adaptive) immunity — specifically vaccine-induced active immunity which helps her immune system recognise and destroy the measles virus on exposure.

Answer 2: Vaccinated children develop immune memory (antibodies and memory cells) that act quickly to prevent infection or reduce severity, thereby stopping disease progression.

Answer 1: Self-medication can be risky because wrong drug choice, incorrect dosage, and incomplete courses encourage survival of resistant bacteria. Antibiotics do not treat viral infections.

Answer 2: Possible causes: (a) Infection may be viral (antibiotics ineffective); (b) incomplete or inappropriate antibiotic use can select resistant bacteria causing relapse or worsening; (c) complication or secondary infection.

Answer 1: Water-borne diseases include cholera, typhoid, dysentery (amoebic and bacillary), and hepatitis A — all caused by microbes entering via the faecal–oral route.

Answer 2: Preventive measures: (a) Boil or chlorinate drinking water; (b) construct a covered and protected water source with proper drainage; (c) improve sanitation and ensure safe disposal of human waste; promote handwashing.

Answer 1: No — this is a non-infectious allergic reaction. Allergies are caused by the immune system reacting to harmless substances (allergens) and are not transmitted person-to-person.

Answer 2: Likely cause: food allergy (nut allergy) triggering histamine release. Immediate step: remove exposure, give antihistamine (if prescribed) and seek medical help if symptoms are severe (difficulty breathing).

Answer 1: The immediate response is inflammation. Redness and swelling occur due to increased blood flow and accumulation of fluid and white blood cells (phagocytes) at the injury site to fight microbes and begin repair.

Answer 2: Not always dangerous — inflammation is a normal protective response. However, spreading redness, pus, high fever, or severe pain could indicate a serious infection needing medical care.

Answer 1: Patient A (with pus and localized swelling) is more likely to have a bacterial infection since pus formation often indicates bacterial involvement.

Answer 2: Antibiotics should be used carefully to avoid development of antibiotic resistance, unnecessary side effects, and because they are ineffective against viruses (patient B may have a viral illness).

Answer 1: Consider vector-borne diseases — e.g., malaria, dengue, chikungunya, all transmitted by mosquitoes.

Answer 2: Prevention: (a) Remove stagnant water and use mosquito nets/repellents; (b) community measures like fogging, covering water storage and wearing protective clothing.

Answer 1: Vaccination induces immunity in individuals and, when coverage is high, leads to herd immunity reducing disease transmission and protecting unvaccinated people.

Answer 2: Other measures: surveillance to identify cases, isolation of infected persons, health education, sanitation, and ensuring safe water and hygiene practices.

Answer 1: Rapid onset in hours suggests a foodborne toxin (pre-formed toxin like staphylococcal enterotoxin) or short-incubation bacterial intoxication. Some infections also have short incubation, but toxin-mediated illness is likely.

Answer 2: Advice: Seek medical care, maintain hydration (oral rehydration), collect food samples for testing if possible, and stop serving the suspected food. Improve food handling and hygiene.

Answer 1: Poor sanitation allows faecal contamination of environment and water leading to transmission of diarrhoeal pathogens (faecal–oral route), causing frequent stomach upsets.

Answer 2: Fixes: (a) Repair and clean toilets, ensure water supply and handwashing facilities with soap; (b) improve drainage, cover open drains and keep food areas separate from toilets.

Answer 1: An asymptomatic carrier harbours the pathogen without showing symptoms but can transmit it to others. It is dangerous because carriers unknowingly spread disease.

Answer 2: Steps: Screen food handlers, treat Raj with appropriate antibiotics if indicated, temporarily suspend him from food preparation, educate on hygiene, and ensure proper food safety practices.

Answer 1: Likely cause: fungal infection (ringworm) spread by direct contact or via contaminated towels (fomite transmission).

Answer 2: Prevention: Avoid sharing personal items, launder towels frequently, disinfect equipment, maintain personal hygiene, and treat infected persons promptly.

Answer 1: The sibling with a balanced diet is likely to have stronger immunity because proper nutrition provides vitamins, minerals and proteins needed for building immune cells and antibodies.

Answer 2: Recommendations: Include fruits and vegetables (vitamin C, A), protein-rich food (eggs, pulses), and adequate fluids; limit processed snacks and ensure a variety of nutrients.

Answer 1: RDTs are quick, simple, require minimal equipment and provide fast results, making them valuable where advanced laboratory facilities are absent.

Answer 2: Next steps: Begin appropriate antimalarial treatment as per guidelines, report the case for public health surveillance and, if needed, confirm with microscopy when available.

Answer 1: Respiratory hygiene (covering coughs, masks, handwashing) reduces droplet spread of the influenza virus from person to person.

Answer 2: Seasonal vaccination primes the immune system against circulating strains, reducing infection risk and severity and lowering transmission.

Answer 1: Early detection ensures timely treatment, reduces complications and transmission, and improves cure rates. TB is contagious through airborne droplets from active cases.

Answer 2: Awareness encourages people to seek care, complete treatment (preventing drug resistance), and reduces stigma so that infected individuals come forward for testing and therapy.

Answer 1: Pollutants irritate airways, reduce lung function, exacerbate asthma and can increase risk of chronic bronchitis and other respiratory illnesses.

Answer 2: Actions: enforce emission controls at the factory, plant trees as a buffer, inform residents about protective masks and reducing outdoor activity during high pollution periods.

Answer 1: Community involvement ensures rapid action, better compliance with preventive measures, local knowledge helps targeted interventions and speeds up reporting and control.

Answer 2: Prioritised actions: (a) ensure safe drinking water and sanitation; (b) promote hygiene and handwashing; (c) coordinate with health authorities for case management and monitoring.