Why most AIDS in Punjab trace back to truck drivers?

With India catching up to Africa in the number of AIDS cases, and Punjab is no exception. Even the village I hail from, two or three families have suffered losses. One most common thing I have started to notice from news and cases like in my village is that most of the wives or kids are related to truck drivers. I wonder, if these Punjabi truck drivers are having extra marital affairs while on route all over India? I wish government or some university would do some study on this pattern. Anyways, read if you like :

http://www.sikhtoons.com/AidsInPunjab.html

Mother of Punjab AIDS victim seeks justice - The Tribune (November 30, 2005)
She is HIV+ but faces no stigma in her Punjab village - The Tribune (December 2, 2005)
Indian minister says concerned about AIDS awareness - Alternet.org (November 30, 2005)

taken from www.Sikhnet.com