[1] Although the school in Niterói also had poor scientific equipment, his teachers were enthusiastic and Pereira worked toward a microbiology degree with the help of Arlindo de Assis and A. Monteiro Filho.

After compulsory military service, which he served in a cavalry regiment, the Dragões da Independência, Pereira returned and graduated with honors.

[1] In England, he worked in the University of Manchester's department of microbiology under virology pioneer Hugh Bethune Maitland and bacterial taxonomist Samuel Tertius Cowan.

[1] He said about this time, "Although this period of postgraduate training did not lead to formal qualifications or published papers, it was certainly one of the most satisfactory and rewarding stages of my professional career".

[1] He married in 1946 and returned to Rio de Janeiro the following year,[1] beginning work as a clinical pathologist at a government hospital.

Pereira soon left this position to join a research team directed by J. Travassos at the Instituto Oswaldo Cruz, studying rickettsia as a part-time assistant.

[1] At the institute, Pereira helped demonstrate the presence of murine typhus and tick-transmitted Rocky Mountain spotted fever in the state of Rio de Janeiro.

[1] Political interference at the institute frustrated Pereira, who moved back to Britain in 1951 to work at the Medical Research Council's Common Cold Unit at Harvard Hospital in Salisbury.

The importance of Pereira's work was recognised in 1961, when he became a director of the World Influenza Centre in Mill Hill at the time of the Asian flu pandemic.

With his wife Peggy, who as Head of Virology at the PHLS in Colindale had responsibility for influenza surveillance in England and Wales, methods were developed to identify new strains and indicate those required for future vaccines.

[4] He assisted and advised young scientists about local health problems between 1979 and 1985, developing new methods and discovering new viruses with his colleagues.

[1] Pereira's wife, Peggy, organised a study of viruses which caused acute respiratory illnesses in Rio de Janeiro children at this time.

[1] Shortly after Peggy retired from the Public Health Laboratory Service in 1987, she and Pereira were involved in a serious car accident in Rio de Janeiro.

[1] Pereira worked with Roger Glass on characterizing unusual picobirnaviruses found in the feces of HIV patients in Brazil.