Do you have to worry about airborne disease on an international air flight?
I'm afraid you're probably not going to like the answer! And really, the model makes little or no difference.

The MITRE Corporation did some studies on this and a good summary can be found in the article
Detecting Aircraft Pathogens Before It's Too Late

The summary points are


  the researchers determined that most particles stayed suspended in the aisle, so when booking a trip, take a window seat


and


  Particles also did not travel far outside the contaminated row, and if they did, it was across the row. Previously, it was thought that contaminants would travel front to back, or back to front. 


Most worryingly:


  The need for such sensors was evident in the 2003 outbreak of Severe Acute Respiratory Syndrome (SARS), which originated in an Air China flight from Hong Kong to Beijing, spread through 18 countries, and resulted in 774 fatalities. Asian economies suffered $11 billion in damages


As for controlling pathogens on board an aircraft, the CDC provide guidance which involves the same procedures you'd use on the ground (Hand washing, PPE, handling of bodily fluids). 

Although air is no doubt filtered, as far as I know there is nothing special about the filters used on Aircraft that would be unique to aviation, nor offer any additional defense against airborne pathogens.