In another trial called PrEP -- pre-exposure prophylaxis -- the CDC is also studying whether antiretroviral pills are safe and effective in preventing HIV infection.

CNN: Gel cuts HIV transmission rate in study

"For example, hiking in a rural area of the Indian subcontinent where dogs commonly roam free carries a sufficient risk of exposure - combined with potential difficulties in obtaining early, safe and effective post-exposure prophylaxis - to warrant vaccination before travelling, " he said.

BBC: NEWS | Health | Rabies warning over minor bites

If there is concern about an exposure to rabies, prophylaxis consisting of rabies immune globulin (an injection that contains human antibodies against the rabies virus) and rabies vaccine (four injections over the course of two weeks) is recommended.

CNN: Are rabies shots needed for any bat exposure?