ENVIRONMENTAL BIOLOGICAL HAZARDS IN THE PACIFIC BASIN

David Koh
Professor and Head
Department of Community, Occupational and Family Medicine
Faculty of Medicine, National University of Singapore

Several viral diseases have recently emerged in various countries in the Pacific basin. These include Henipavirus (Hendra and Nipah viruses), Coronavirus (SARS coronavirus) and Influenza (H5N1) viral infections

Environmental and occupational exposures are relevant in many instances. For example, horse breeders, pig farmers and abbatoir workers may be exposed to Hendra and Nipah viruses at work. For Severe Acute Respiratory Syndrome (SARS), the most significant occupational groups at risk are the various categories of health care workers. Other occupationally exposed persons may include food handlers, transport workers and laboratory workers. H5N1 avian influenza poses a risk to workers (and their families) who are in direct contact with infected poultry or other animals (e.g. pigs).

These illnesses can be severe with high mortality rates. For instance, Nipah virus infection presents as encephalitis. 265 cases were reported in Malaysia in 1998-99, of whom 105 patients died (40% mortality). SARS and avian influenza infections can result in severe acute respiratory distress. The mortality rate for SARS is about 11%, with 916 deaths among 8,422 cases reported in the global outbreak that affected 29 countries. The mortality for human cases of avian influenza is even higher (58%). Between 28 Jan 2004 to 17 June 2005 , one hundred and seven cases of laboratory confirmed cases of human H5N1 avian influenza have been reported to the World Health Organization, with 54 deaths.

These viral outbreaks may recur or appear to be ever present. Hendra virus infection first appeared in Australia in 1994, and recurred in 1995 and 1999. Nipah virus infection was first experienced in Malaysia in 1998 and 1999, and also spread to Singapore . In 2004, Nipah virus infection re-appeared in Bangladesh among children who were in close proximity to fruit bats that harbored the virus. The earliest cases of SARS were recorded in China in 2002, and spread throughout the world in 2003. After its containment, there were at least 3 isolated outbreaks in 2003 and 2004 among laboratory workers. Human cases of H5N1 avian influenza were first seen in 1997 in Hong Kong , and recurred in 1999. Since 2003, sporadic cases have been reported in Southeast Asia , especially in Cambodia , Thailand and Vietnam .