1.   Carried mostly by farm animals, the anthrax disease is naturally transmitted by contact with animal hides through a break in the skin.

2.   Hepatitis B can be transmitted by contact with tainted blood or during sexual relations.

3.   The Singapore government said there was no danger of the disease spreading to the general public, as it was likely transmitted by contact with infected live pigs.

4.   The virus can also be transmitted by contact between animals, through the air or through contaminated feed.