Which of the following is not a Zoonotic disease?

Correct — option (1), Mucormycosis.

WHO's fact sheet on zoonoses (29 July 2020) defines a zoonosis as "an infectious disease that has jumped from a non-human animal to humans."

Mucormycosis does not come from animals. The US CDC describes it as a serious but rare fungal infection caused by moulds called mucormycetes, which live throughout the environment; people get it through contact with fungal spores. CDC states: "Mucormycosis can’t spread between people or between people and animals."

So the disease that is not zoonotic is Mucormycosis.

The idea to remember: a zoonosis jumps from animals to humans; mucormycosis comes from moulds in the environment.

Why the others are wrong

• (2)
  Rabies — Rabies is zoonotic. WHO's rabies fact sheet (17 May 2021) calls it "a vaccine-preventable, zoonotic, viral disease."

  It spreads to people and animals through bites or scratches, usually via saliva, and domestic dogs are responsible for up to 99% of transmissions to humans. Once clinical symptoms appear, WHO says rabies is virtually 100% fatal.

• (3)
  Plague — Plague is zoonotic. WHO's plague fact sheet says it is caused by the bacterium Yersinia pestis, "a zoonotic bacteria usually found in small mammals and their fleas."

  Humans can be infected through the bite of infected fleas, unprotected contact with infectious body fluids or contaminated materials, or respiratory droplets from a patient with pneumonic plague.

• (4)
  SARS — SARS is zoonotic in origin. WHO's travel-health page on SARS says SARS-CoV is thought to be an animal virus from an as-yet-uncertain reservoir, perhaps bats, that spread to other animals (civet cats).

  It first infected humans in the Guangdong province of southern China in 2002. WHO describes SARS as a viral respiratory disease caused by a SARS-associated coronavirus.

WHO describes zoonoses as diseases or infections naturally transmissible from vertebrate animals to humans, with over 200 known types. Their pathogens may be bacterial, viral or parasitic, and they can reach people through direct contact, food, water or the environment.

The label depends on where the pathogen comes from, not on the type of germ. Rabies (virus), plague (bacterium) and SARS (virus) all trace to animals.

Mucormycosis is caused by environmental moulds and, CDC says, does not pass between people and animals.

Key facts

• WHO: a zoonosis is an infectious disease that has jumped from a non-human animal to humans; over 200 types are known.
• CDC: mucormycosis is a fungal infection caused by mucormycetes, moulds that live throughout the environment, and it cannot spread between people and animals.
• WHO: rabies is a vaccine-preventable, zoonotic, viral disease; domestic dogs cause up to 99% of transmissions to humans.
• WHO: plague is caused by Yersinia pestis, a zoonotic bacterium usually found in small mammals and their fleas.
• WHO: SARS-CoV is thought to have come from an animal reservoir, perhaps bats, via civet cats, first infecting humans in Guangdong, China, in 2002.

Common traps

• Germ type does not decide the label: WHO says zoonotic pathogens may be bacterial, viral or parasitic; what matters is whether the disease comes from animals.
• Linked to COVID-19 is not animal-borne: ICMR's 2021 advisory concerned mucormycosis in the COVID-19 period, but the infection comes from environmental fungal spores.
• Person-to-person spread does not cancel a zoonosis: WHO says pneumonic plague can pass between people, yet plague is a zoonotic disease.

• practice — not a real PYQ

  According to WHO, plague is caused by –

  • (a)Vibrio cholerae
  • (b)Yersinia pestis
  • (c)Salmonella typhi
  • (d)Mycobacterium tuberculosis
  Answer(2) — WHO's plague fact sheet names the bacterium Yersinia pestis, usually found in small mammals and their fleas. Options (1), (3) and (4) are not the bacterium WHO names for plague.
• practice — not a real PYQ

  Which of the following did ICMR's 2021 advisory list among conditions that predispose a person to mucormycosis?

  • (a)Uncontrolled diabetes mellitus
  • (b)Regular physical exercise
  • (c)A diet rich in vitamin C
  • (d)Owning a pet dog
  Answer(1) — ICMR's advisory lists uncontrolled diabetes mellitus first among predisposing factors, along with steroid immunosuppression and prolonged ICU stay. Options (2), (3) and (4) are not on its list, and CDC says mucormycosis does not spread between people and animals.