BIOLOGICAL HAZARDS is one of the 5 categories of Health Hazards (The other 4 are: Chemical, Ergonomics, Physical & Psychosocial).
Biological hazard is any living organism that can cause harm to our health such as virus ( e.g. H1N1 which cause Influenza A H1N1 infections at the moment), bacteria (e.g. Mycobacterium tubercule which cause Tuberculosis) et cetera.
One thing we should remember of Biological hazards is it has no threshold exposure value or in another word it has no PEL value as for chemical hazards. At any value, biological hazards can cause disease, this especially true for H1N1 virus of which everybody does not have antibody. Generally to control the infection of biological hazards, we must break the infection chain.
We can divide infection by biological hazards into three types (depends on their mode of transmission) : 1. blood-borne infection (transmit through blood e.g. Hepatitis B which causes hepatitis), 2. oral-fecal infection (transmit via mouth & stool e.g. Salmonella which causes Typhoid) and 3. air-borne infection (transmitted via air e.g. TB which causes Tuberculosis).
For Influenza A H1N1 infection, it is caused by the droplet which contains the virus from the cough and sneeze of the infected person. The droplet can be transmitted via direct cough to the contact person through the air if another person stays within one meter distance. This social distance of one meter is including the 'breathing zone'. Besides that the person who cough out the virus can transmit it via his hand if he cough directly on his hand.
This is the reasons why the authority advise us to practise personal hygiene, respiratory hygiene or cough etiquette, stay more than one meter distance from the person who has cough or other symptoms of H1N1.
These control measures are the basic things we need to practice during this pandemic time. If you have the symptoms: practise personal hygiene - wash you hand with soap, if you have cough make sure you practise cough etiquette - when you cough or sneeze, cover your mouth or nose with a tissue paper then throw it into the dust bin and if possible dont attend any gathering or the crowd. However, if unavoidable, please use face mask. In another word, quarantine youself at home. Practicing this control measures is every one responsibility. At this point of time, we need to be VIGILANCE but do not PANIC.