CDS (I) 2020 General Knowledge · Question 14 of 120

Correct — D, Elephantiasis. An epidemic is a rapid rise of a disease to a large number of cases in a population within a short period. Cholera, malaria and smallpox all behave that way — cholera flares after floods and in crowded camps, malaria surges in transmission seasons and after population movement, and smallpox spread explosively from person to person until vaccination stopped it. Elephantiasis does not. It is the late, disfiguring swelling of lymphatic filariasis, and it builds only after repeated infected mosquito bites over months or years, with the worms taking about a year to mature and then living five to eight years. A condition that needs years of repeated exposure in one place cannot produce the short, sharp curve that defines an epidemic; it is endemic instead, held at a steady level wherever the vector and the parasite persist.

• (a)Cholera — A textbook epidemic disease. Contaminated water carries it, and case numbers can climb within days of a breakdown in sanitation.
• (b)Malaria — Endemic across much of the tropics, but it also breaks out in epidemics when rainfall, migration or a collapse in control raises transmission sharply. The paper treats it as an epidemic disease.
• (c)Smallpox — The historical epidemic disease, spread directly between people. It was declared eradicated worldwide in 1980, but the question is about its epidemic character, which is not in doubt.

Three words describe how much disease is present and how fast. Endemic means a disease held at a steady baseline in an area without outside input. Epidemic means a sharp rise well above that baseline in a short time. Pandemic means an epidemic that has crossed countries or continents. The same disease can be endemic in one setting and epidemic in another, so the label describes the pattern of occurrence, not the pathogen.

The item works by putting three fast-spreading infections beside one slow, chronic one. What sets elephantiasis apart is its natural history: the worms Wuchereria bancrofti, Brugia malayi and Brugia timori are delivered by mosquito bite, take about a year to become adults, and the visible swelling arrives only in a minority of long-infected people. As of 2022 roughly 40 million people were infected and about 863 million in 47 countries were at risk, which is a large, stable burden rather than an outbreak. One point of honesty about the framing: malaria in India is more accurately endemic with seasonal epidemic peaks, so option (b) is defensible only under the loose sense of epidemic that school textbooks use. The key names elephantiasis, and it is the clearest answer on the list because it is the only one that cannot spread in a burst at all.

• An epidemic is a rapid spread of disease to a large number of hosts in a population within a short period.
• An endemic infection is one maintained at a baseline level in an area without external input.
• Elephantiasis is the swelling caused by lymphatic filariasis, whose worms are carried by mosquitoes of the genera Aedes, Anopheles, Culex and Mansonia.
• Wuchereria bancrofti causes about 90 per cent of lymphatic filariasis cases; adult worms live five to eight years and take roughly a year to mature.
• About 40 million people were infected as of 2022, with around 863 million at risk across 47 countries; smallpox by contrast was declared eradicated in 1980.

• Judging by how serious a disease is rather than by how fast it spreads.
• Assuming any mosquito-borne disease behaves like malaria; filariasis needs repeated bites over years.
• Treating endemic as a synonym for widespread; it is a statement about steadiness, not about size.

As an odd-one-out among named diseases, or as a definition item asking which term fits a described pattern of occurrence.

• practice — not a real PYQ

  The parasite responsible for the large majority of cases of lymphatic filariasis is

  • (a)Plasmodium vivax
  • (b)Wuchereria bancrofti
  • (c)Ascaris lumbricoides
  • (d)Entamoeba histolytica

  Answer(b) Wuchereria bancrofti — a nematode carried by mosquitoes, responsible for about 90 per cent of lymphatic filariasis.

• practice — not a real PYQ

  A disease that is constantly present at a baseline level in a particular area, without being introduced from outside, is described as

  • (a)epidemic
  • (b)pandemic
  • (c)endemic
  • (d)sporadic

  Answer(c) endemic — a steady, self-sustaining level of infection in that area.