Birds can be  infected by many diseases that affect their lungs and respiratory system.  Birds lungs and respiratory system can be infected by many parasites. One such parasitic infection   is known as Air Sac Mites ( Sternostoma tracheacolum). This parasites lodge themselves all the way from the cere/nostrils to the lungs and the tiny air sacs in the lungs.
Air sac mites are transmitted through  air or close contact with an infected bird.
Like sneezing or coughing or through an infected bird contaminating the drinking water. This mites can also passed on between breeding pairs and their chicks due to  regurgitation of feed.
Most commonly affected birds by this parasites are Canaries, Gouldian finches, Finches. Budgerigars and Cockatiels. But it is also known to infect other birds also.Symptoms 
The symptoms for air sac mites depend on the severity of the parasitic infection. Birds with mild infection may not show any signs but those with acute infection will show symptoms 
Tail bobbling
Gasping (Open mouth breathing)
Clicking sound white breathing.
These symptoms are aggravated in the infected bird, when the bird is stressed or handled. 
A very acute infection can kill the bird due to suffocation.
Some other symptoms for air sac infection in Canaries is that they stop singing.
The bird appears fluffed up and dull. 
Poor feather condition
Weight loss.
One way to check for Air sac mites is hold the bird in your hand or near the ear. You can feel / hear a clicking out every time the bird exhales.
The main source of transmission for this disease is contaminated drinking water, Contact and Air. Air Sac mites are transmitted through the air or by close contact with an infected bird. Coughing or sneezing by the infected bird releases a tiny mist of moisture that contains the air sac mites. Through adult courtship feeding and parents feeding their chick.
Ivermectin ( specially formulated for birds) . Procedure -. After the first application it has to be repeated on the 12th day. The first application kills the mites but not the eggs. The second application kills the mites that hatch from the eggs that were unaffected. . The usual vet recommendation is to treat the birds twice a year, or once every 4 months in humid / warm climates.There is usually an improvement within 24 hours after the first course of treatment. During treatment, it is important to clean the drinking containers thoroughly as the bird could get re-infected via a contaminated drinking container. Even after proper effective treatment with medication.
It is common for birds to be infected by parasites like mites and lice. This parasites can infect a bird as small as finch to as large as macaws. But majority of pet birds are free from them, But there is a possibility that they can be infected by coming into contact with an infected bird. Humans can be a source of infection. They can pass on the parasites unknowingly after they have handled an infected bird from the wild or other source,This parasites can not survive for long outside the host body. This parasites do not survive on human body for long. But they can bite causing inflammation of skin, itching or mild skin infection.
Airsac mites are found naturally in the Gouldian finch (E. gouldiae) and 6 co-occurring species (long-tailed finches (Poephila acuticauda), masked finches (P. personata), pictorella manikins (Heteromunia pectoralis), zebra finches (Taeniopygia guttata), double-barred finches (T. bichenovii) and budgerigars (Melopsittacus undulatus) (P.J.Bell 1996). The prevalence and intensity of infection in Gouldian finches is significantly higher than in other species except Pictorella manikins (P.J.Bell 1996).