Although the Argentine parrot trade was stopped, a number of birds were illegally sold on to visitors at its seaports, with the consequence that psittacosis was transmitted to several countries.

The impact of the outbreak on the U.S. Hygienic Laboratory, with 16 of its workers affected, including two deaths, led to the formation of the National Institute of Health.

[2][3][4][5] Subsequently, further similar outbreaks with a coincidence of exposure to birds appeared in other parts of Europe, including Paris in the 1890s, where it killed one in three affected people.

Prior to the 1929 outbreak of psittacosis in the United States, the last known cases were in 1917, found in captive birds in the basement of a department store in Pennsylvania.

[4] Affected people typically experienced headache, poor sleep, fatigue and a cough trailing several days of fever.

[9][10] By early 1930, the disease was reported in humans in several countries around the world, accelerated by the popular hobby of domestic bird-keeping at the time.

[2][11] The majority of cases in the U.S. were found in 1931 to be linked to endemic psittacosis in California, associated with the increasingly popular trade of breeding lovebirds for sale chiefly to housewives and widows.

[12] When cases appeared in Amsterdam, Netherlands Health Department asked that steamships that call at South American seaports refuse to take on board parrots.

[2] In the UK, the Parrots (Prohibition of Import) Regulations, 1930 was created following consideration by the permanent committee of the Office international d'hygiène publique.

[19] In 1929, around 500,000 canaries and nearly 50,000 parrots were imported to the United States from Brazil, Argentina, Colombia, Cuba, Trinidad, Salvador, Mexico and Japan.

[2] In early January 1930, an outbreak of "mysterious pneumonias" in the United States came to media attention when cases in three members of one family were traced to the previous Christmas importation of parrots from South America.

In consequence, Martin's physician sent a telegram to the United States Public Health Service (PHS) in Washington DC, requesting for advice on parrot fever.

The story came to the attention of Surgeon General Hugh S. Cumming, who received similar messages from Baltimore, New York, Ohio and California.

[11][24] On 11 January, the same paper reported "Parrot Disease Fatal to Seven",[2] and the Chicago Daily Tribune put on their front page "Baltimore woman dies".

[11][24] Reports soon began to follow from the eastern coast of the U. S., with Baltimore, New York City and Los Angeles, involving other birds such as shell parakeets (Australian budgerigars).

[2] Six major pet dealers in the U.S. stood to make a loss of $5 million per year as a result of an executive order issued by President Herbert Hoover on 24 January prohibiting "the immediate importation of parrots into the United States, its possessions and dependencies from any foreign port", until research could find the cause and mode of transmission.

[4] The following day, bacteriologist William Royal Stokes died, only weeks after commencing research on the parrot dropping samples given to him by Armstrong.

They had failed to isolate the causative infectious agent, and McCoy was subsequently forced to kill the birds and fumigate the Hygienic Laboratory.

Later, it was discovered that the main source was domestic lovebirds raised in hundreds of independent Californian aviaries by breeders who were supplementing their incomes following the recent Wall Street Crash.

Likewise, the "hysteria" and heightened public concern surrounding the pandemic may not have occurred had it not been for headlines such as "Killed by a Pet Parrot".

[14] During the summer and autumn of 1929, Córdoba and Tucumán in Argentina, reported over 100 cases of a severe atypical pneumonia linked to a large shipment of birds from Brazil.