More about masks and flu transmission

I really need to learn to read...

How can masks be effective in preventing spread of viral infections, when viral particles are so small and when experiments with guinea pigs show that coughing and sneezing aren't required for transmission?

From the PNAS journal article:

"Our results indicate that droplet transmission of influenza virus occurs between guinea pigs..."

Granted, I haven't dug into the article for information on the droplets' sizes, but this suggests all kinds of variables to examine: mask porosity, how vapor/droplets condense onto masks, etc.

More anecdotal evidence on the effectiveness of masks in preventing secondary pneumonia, at least, comes from "The Great Influenza". From page 211:

"Capps did write the JAMA article. He reported finding the masks [used by patients with respiratory disease at Camp Grant near Rockford, IL] so successful that after less than three weeks of experimenting he had abandoned testing and simply started using them 'as a routine measure'."

They didn't always work. Page 215, describing the September 1918 wave of infection:

"Despite all precautions, despite wearing surgical masks and gowns... 43 percent of the staff... required hospitalization. Ten nurses at this single hospital died."