Measles occurs in mainly which season
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measles seasonal pattern which season peak transmission
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Here is a complete, textbook-backed answer:
Measles - Seasonal Occurrence
Measles does not have a single universal season because the pattern varies by climate zone:
Tropical Zones (e.g., India, Sub-Saharan Africa)
- Most cases occur during the dry season
- Reduced humidity and increased indoor crowding during dry months facilitate droplet transmission
Temperate Climates (Europe, North America)
- Measles is predominantly a winter disease
- Cold weather drives people indoors, increasing close contact and droplet spread
In India Specifically
- Epidemics of measles are common during winter and early spring (January to April)
- This is the most commonly tested answer in Indian medical/nursing exams
Why This Seasonal Pattern?
- Crowding indoors during cold/dry months amplifies droplet transmission
- School term cycles concentrate susceptible children
- Waning mucosal immunity in colder, drier air
Key point from Park's Textbook of Preventive and Social Medicine: "Given a chance, the virus can spread in any season. In tropical zones, most cases of measles occur during the dry season. In temperate climates, measles is a winter disease, probably because people crowd together indoors. Epidemics of measles are common in India during winter and early spring (January to April)."
- Park's Textbook of Preventive and Social Medicine, p. 167
The ECDC also confirms that measles infections typically peak during late winter and early spring in Europe as well.
Summary Table
| Region | Peak Season |
|---|---|
| Tropical (India, Africa) | Dry season |
| India (exam answer) | Winter - Early Spring (Jan-Apr) |
| Temperate (Europe, USA) | Late Winter - Spring (Feb-May) |
City gets supply from impounding reservior
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This is a question about water supply sources from the field of Preventive & Social Medicine (Community Medicine). Here is a full answer:
Cities That Get Water Supply from Impounding Reservoirs
Mumbai, Chennai, and Nagpur are the classic examples of Indian cities that derive their water supply from impounding reservoirs.
"Cities such as Mumbai, Chennai and Nagpur derive their water supply from impounding reservoirs."
- Park's Textbook of Preventive and Social Medicine
What is an Impounding Reservoir?
An impounding reservoir is an artificial lake constructed using earthwork or masonry in which large quantities of surface water are stored. Dams built across rivers and mountain streams also serve this purpose.
- The area draining into the reservoir is called the "catchment area"
- The catchment area must be kept free from human and animal intrusion to prevent contamination
Characteristics of Impounding Reservoir Water
| Feature | Description |
|---|---|
| Quality | Fairly good - ranks next to rainwater in purity |
| Appearance | Usually clear and palatable |
| Hardness | Usually soft |
| Pathogens | Considered free of pathogenic organisms |
| Color | May acquire brownish color if surrounding hills are covered with peat |
Disadvantage
The main disadvantage of storing water for long periods is the growth of algae and other microscopic organisms, which impart bad tastes and odours to the water.
Impurities
- Derived from the catchment area
- Sources: human habitations, animal keeping or grazing
- Even without human habitation, wild animals can cause contamination
- Mountain streams are not necessarily pure despite popular belief
Comparison: Other Surface Water Sources in Indian Cities
| Source | Cities | Key Feature |
|---|---|---|
| Impounding Reservoirs | Mumbai, Chennai, Nagpur | Best quality surface water |
| Rivers | Delhi, Kolkata, Allahabad | Grossly polluted, needs treatment |
| Tanks/Ponds | Rural villages | High contamination risk |
- Park's Textbook of Preventive and Social Medicine, p. (Water Supply section)
Niacin present absent im
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niacin present absent food sources milk egg maize corn nutrition
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Here is a complete, exam-oriented answer on Niacin (Vitamin B3) - Present/Absent in Foods:
Niacin (Vitamin B3) - Food Sources: Present vs. Absent
Foods RICH in Niacin (Present)
| Food | Notes |
|---|---|
| Meat (beef, pork, poultry) | Best sources, 5-10 mg per serving |
| Fish | Excellent source |
| Liver | Very high content |
| Whole grains / Enriched bread | Fortified with niacin |
| Nuts (especially peanuts) | Good plant source |
| Mushrooms | Good vegetarian source |
| Dried beans / Legumes | Moderate source |
| Yeast | Rich source |
| Dairy products (milk) | Moderate - also rich in tryptophan (precursor) |
| Eggs | Rich in tryptophan (precursor) |
Key point: Milk and eggs are not high in niacin directly, but are rich in tryptophan (60 mg tryptophan → 1 mg niacin), so they serve as good indirect sources.
Foods LOW/ABSENT in Niacin (or Niacin Unavailable)
| Food | Reason |
|---|---|
| Corn / Maize | Contains bound niacin - unavailable for absorption without alkaline hydrolysis |
| Jowar (Sorghum/Millet) | Has adequate niacin, BUT high leucine content interferes with tryptophan → niacin conversion |
| Polished rice | Low in niacin |
Why Mexicans don't get pellagra despite eating maize: They wash maize in lime water (alkaline hydrolysis), which releases the bound (complexed) niacin and makes it bioavailable - a process called nixtamalization.
Key Exam Points
- Pellagra = niacin deficiency disease (4 D's: Dermatitis, Diarrhea, Dementia, Death)
- Classic diet causing pellagra: corn bread + molasses + pork fat (as seen in early 1900s southern USA and still endemic in parts of India, China, South Africa)
- Niacin synthesis: Body can make niacin from tryptophan - this is why protein-rich diets (meat, dairy) protect against pellagra
- Isoniazid (TB drug) can cause niacin deficiency by interfering with tryptophan metabolism
- Hartnup disease: Defective tryptophan absorption → pellagra-like symptoms
- Carcinoid syndrome: Excess tryptophan diverted to serotonin synthesis → niacin deficiency
Summary (One-liner for Exams)
Niacin is present in: meat, fish, liver, whole grains, nuts, mushrooms, legumes Niacin is absent/unavailable in: corn/maize (bound form), jowar (leucine blocks conversion) Rich in tryptophan (indirect niacin): milk, eggs
- Fitzpatrick's Dermatology, Vol. 1 (Vitamin B3/Niacin section)
- Sleisenger & Fordtran's GI and Liver Disease
- NIH Niacin Fact Sheet
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