I have question bothering me about an instance that happened with me in the evening. I visited my local grocery store in the evening and as i was getting something off the shelf, i brushed my hand along the shelf. At that time I did not make much of it and continued shopping. A couple of hours later, while watching TV at home, I noticed a cut on the thumb of the same hand. I'm really bothered by the possibility that someone, who might be infected by HIV,   may have gotten cut the same way just few minutes before me. What is the risk of acquiring the infection in this possibility? What should I do?

Welcome to our Forum.  I'll be glad to comment.  I would urge you not to be concerned about this event.  We receive many questions from persons who have accidently cut or scraped themselves when they are out and about, worried that they might have been exposed to HIV, hepatitis C or some other blood borne infection.  The fact however is that there are no instances in which HIV has been transmitted in this way and it is really not something to worry about.  There are many reasons which make this the case.  Some of them are:

1.  HIV is rather rare, more people do not have HIV or hepatitis making it unlikely that someone with infection had recently cut themselves as you did.

2.  HIV rapidly becomes infectious upon exposure to the environment due to drying and the lower than body temperature of the environment.

3. Most cuts and scrapes of this sort are rather superficial and for infection to occur, infected material must get deep into tissue where it can gain access to the blood stream.

In summary then, I would not worry about this event and see no medical need for testing.  Your risk of getting HIV from this exposure is less than your risk of being struck by lightening- I trust that neither will happen to you.  Please don't worry.

I hope that this comment is helpful.  EWH

I would like to know how deep should a cut be by an infected sharp in order to acquire the infection? 

Is an infected needle the only form of sharp that can transmit the virus?