Communicable Disease Nursing

Why A is correct

Microfilariae, the tiny larval offspring of the adult filarial worms, circulate in the blood mostly at night. A smear drawn then is most likely to catch them.

Why the other options are wrong

• B — "In the early morning": This timing works for a sputum smear in tuberculosis and for the pinworm tape test, not for filariasis.
• C — "At midday": Midday is the collection window for Loa loa, a different filarial worm found in Africa.
• D — "Right after a fever spike": Filarial larvae follow a night-time cycle, not the fever curve, so a fever spike does not tell you when they are in the blood.

Why C is correct

The pertussis exposure is the droplet one: an unmasked visitor stands within the meter those large droplets travel.

The route depends on the particle the organism rides on, not on how close the two people stand. Large droplets are pushed a short distance and then fall out of the air, so they reach only people nearby. Droplet nuclei are tiny particles small enough to stay floating in the air and drift. That makes them airborne, however close or far the contact is. A route can also be indirect, when the organism is picked up from a soiled object instead of from the air. Pertussis is carried on large droplets, so a bedside cough is the droplet example.

Why the other options are wrong

• A — "A tuberculosis patient coughs during a bedside assessment while the nurse stands unmasked": Tuberculosis travels on droplet nuclei that stay floating in the air, so this exposure is airborne. Standing close does not turn an airborne organism into a droplet one. It is true that this exposure is respiratory, unprotected and within a meter, but the particle size, not the distance, decides the route.
• B — "A measles patient coughs in the waiting area beside an unimmunized toddler": Measles is also carried on droplet nuclei that stay floating in the air. The exposure is airborne, not droplet, even though the contact is close.
• D — "An influenza patient's used tissue is handled by a nurse who then rubs her eye": The route here is indirect contact with a soiled object, and nothing expelled into the air is breathed in. The organism is a respiratory one, but here it does not travel through the air.

Why B is correct

Diphtheria on droplet precautions is the correctly matched pairing.

Diphtheria spreads on the large droplets produced when a patient coughs, sneezes or talks. Those droplets are heavy enough to fall within about a metre and do not stay suspended. A private room and a surgical mask for anyone working close to the patient are what contain them. Droplets fall within about a metre; airborne particles stay suspended in the room after the patient leaves.

Why the other options are wrong

• A — "Measles — droplet precautions": measles is a respiratory illness that behaves like a droplet disease in almost every other respect, but not in the air it leaves behind. It is the pairing wards most often default to. Measles virus remains suspended and infectious in room air after the patient has left, which is what airborne means. It needs a negative-pressure room and a fitted respirator.
• C — "Pertussis — airborne precautions": pertussis is transmitted by droplets, so airborne containment is one category too far.
• D — "Chickenpox — contact precautions": contact is half of what varicella needs. The virus is airborne as well, and contact measures by themselves leave the room air unmanaged.

Why B is correct

Closing the wound can drive rabies virus deeper into the surrounding tissue, which is why suturing is delayed.

Washing and irrigation act on the wound surface, and the immunoglobulin is infiltrated into and around the wound itself. Stitches push contaminated material inward, past where any of them can reach it. What closure buries past that reach is the virus itself, which is the rabies-specific concern.

Why the other options are wrong

• A — "Delay the infiltration of rabies immunoglobulin around the wound": immunoglobulin really is infiltrated into and around the wound, but this names a downstream problem rather than the reason itself. Early closure can interfere with that step, and the timing problem arises because closure buries the virus deeper.
• C — "Mask early signs of a local wound infection": masking infection is a general concern with any wound closure, not the rabies-specific reason suturing is discouraged.
• D — "Trap contaminated debris against the wound base": trapping debris is a general risk of closing a dirty laceration, not the rabies-specific concern being tested here.

Why A is correct

The ulcers come from lost protective sensation: he keeps injuring his soles without feeling it.

Leprosy damages peripheral nerves, and the loss of protective sensation that follows is one of its cardinal signs. A foot that cannot feel pressure or a stone in a sandal takes the same small injuries every day with no warning. Those injuries accumulate until the skin breaks through its full thickness, which is why the ulcers sit where his weight falls.

Why the other options are wrong

• B — "Poor peripheral circulation causing ischemic breakdown of the plantar skin": ischemic ulcers from diabetic vascular disease are a genuine look-alike on the sole, but leprosy attacks the nerve trunks and foot pulses are typically preserved. This ulcer is neuropathic rather than ischemic.
• C — "Direct bacillary damage to the plantar skin causing necrosis": Mycobacterium leprae targets peripheral nerves and skin appendages, and it does not destroy the sole directly. The break in the skin is the result of injury he never felt.
• D — "Autoimmune reaction against plantar connective tissue triggered by treatment": immune-mediated leprosy reactions are real and can follow the start of treatment, though they are systemic illness rather than a local process. Erythema nodosum leprosum brings fever and crops of new nodules, not a single ulcer under the foot.