Droplet transmission of disease agents

Steps:

• Identify droplet infection as transmission via respiratory droplets from coughing, sneezing, or talking.
• Recall common agents: viruses like influenza (2) and bacteria like Streptococcus pneumoniae (3) spread this way; parasites like Plasmodium (1) do not.
• Match agents to transmission modes: 1 requires vector bite, excluding droplets.
• Select option including only droplet-transmissible agents.

Why D is correct:

• Droplet infection definition limits transmission to airborne respiratory pathogens, matching agents 2 and 3 per CDC guidelines.

Why the others are wrong:

• A includes 1, a non-droplet agent.
• B excludes 3, a droplet-transmissible bacterium.
• C includes 1, incorrectly assuming parasite droplet spread.

Final answer: D