One of the biggest challenges faced in pig biosecurity is the spreading of the PRRS virus by aerosols. Currently biosecurity protocols are successful at preventing the introduction of other swine pathogens, such as transmissible gastroenteritis virus, but they have limited, if any efficacy against PRRSV. This was mostly because no one knew exactly where the virus was coming from and it was believed that once the disease left the host it was harmless to others. The purpose of this article is to summarize attempts to identify regional vectors and routes of PRRSV spread and discuss how these new data may impact future biosecurity protocols and facility designs on swine farms. It has been proven that PRRSV can be transmitted by biological vectors like mosquitoes and house flies. Also both mosquitoes and flies have shown that PRRS can remain viable in their GI tracts. Tests done that invovled infected flies who were released and then baited and trapped at various distances found that flies caught as far as 2.3 km away were PCR-positive. Another possible transmitter of the PRRS virus is transport carriers. Pigs are shipped long distance to slaughter and also come into close contact with other pig herds and cross international and state boarders. Little information exists on this subject so a test was designed to find the potential risks involved with the spreading of PRRS through transport trailers. The experiment involved four treatments: Treatment 1 consisted of a manual scraping of the interior to remove soiled bedding. Treatment 2 consisted of bedding removal, washing, and disinfecting. Treatment 3 consisted of bedding removal, washing, disinfecting as described; however to simulate cold weather conditions, trailers were then frozen overnight at -20 0 C and allowed to thaw. Treatment 4 consisted of bedding removal washing, disinfecting and drying. Following each treatment, naive sentinel pigs were housed in trailers for 2 hours. Only treatment 4 prevented pigs from becoming infected with PRRSV. Scott Dee believes biosecurity for PRRS comes down to four things 1. Having a naive source of breeding stock and semen. 2. Insuring that the interior of the transport vehicle is always dry in every case. 3. Controlling the risk of insect entry. And 4. Controlling the risk of PRRSV-contaminated aerosols. Dee goes on to propose questions that should be asked about biosecurity such as: Should we have different protocols based on season? Do we need to reconsider barn design?  Can we still live with naturally ventilated facilities? and other questions that should be addressed as we battle the PRRS virus.