The Centre for Health Protection said last night it was still seeking a common link between five cases of pneumonia, two of which have proved fatal.
Two pig farmers have died and three Sheung Shui abattoir workers have been taken ill.
Centre consultant Thomas Tsang Ho-fai said a 61-year-old abattoir worker admitted to hospital on December 30 was found to have been infected by the pneumococcus and parainfluenza viruses, common pathogens that cause typical pneumonia.
'In that sense it is a more typical pneumonia rather than atypical pneumonia,' Dr Tsang said.
Pneumococcus and parainfluenza viruses are transmitted by the respiratory route, not by eating contaminated pork, he added. The organisms also do not jump from pigs to humans and the abattoir workers had not been in direct contact with pigs during their work.
'From this angle it seems the chance of the disease jumping from pigs is smaller,' he said.
