The number of people diagnosed with dengue fever (contracted from the bite of…
20142023
The number of people diagnosed with dengue fever (contracted from the bite of a mosquito) in north India is twice the number diagnosed last year. Municipal authorities have concluded that measures to control the mosquito population have failed in this region.
Which one of the following statements, if true, does not contradict this conclusion?
- A.
A high proportion of the affected population has returned from neighbouring countries where dengue is prevalent
- B.
More cases of dengue are now reported because of an increase in the Municipal Office’s administrative efficiency
- C.
Many more cases of dengue are being diagnosed this year since the introduction of a new and effective diagnostic test
- D.
The number of people with malarial fever (also contracted from mosquito bites) has increased this year
Attempted by 42 students.
Show answer & explanation
Correct answer: D
Correct answer: The statement that the number of people with malarial fever has increased this year does not contradict the municipal conclusion.
Reasoning:
The municipal authorities infer that mosquito-control measures have failed because dengue cases doubled compared with last year.
To contradict that inference, a statement must provide an alternative explanation for the rise in dengue that does not involve an increase in the local mosquito population or transmission.
Imported cases or better detection/reporting offer such alternative explanations:
A high proportion of affected people returning from neighbouring countries could mean the increase is due to imported infections rather than failed local control.
More cases reported because of improved administrative efficiency could raise recorded numbers without an actual rise in infections.
Introduction of a new and more effective diagnostic test can increase detected cases by finding infections previously missed.
Why the increase in malarial fever does not contradict the municipal conclusion:
Malaria is also transmitted by mosquito bites; a simultaneous rise in another mosquito-borne disease makes it more likely that mosquito abundance or biting rates have increased locally. That observation is consistent with the view that mosquito-control measures have failed.
(Note: although different mosquito species transmit dengue and malaria, an increase in multiple mosquito-borne illnesses still supports a general failure of mosquito control unless additional information rules out species-specific factors.)
Conclusion: The rise in malarial cases supports the municipal conclusion about failed mosquito-control measures, while the other statements provide alternative explanations for the dengue increase and thus contradict that conclusion.