The proper cooking of pork stems from infections by the trichinella spiralis worm, a parasite found in swine, wild game, etc. that can transfer to the human by way of undercooked meat. It usually only harbors in the fat. Here's some prevention tips from Wikipedia: Prevention
- Cooking meat products to an internal temperature of 165 °F (74 °C) for a minimum of 15 seconds.
- Cooking pork to a uniform internal temperature of at least 144 °F (62.2 °C), per USDA Title 9 section 318.10. It is prudent to use a margin of error to allow for variation in internal temperature and error in the thermometer.
- Freezing pork less than 6 inches thick for 20 days at 5 °F (−15 °C) or three days at −4 °F (−20 °C) kills larval worms.
- Cooking wild game meat thoroughly. Freezing wild game meats, unlike freezing pork products, even for long periods of time, may not effectively kill all worms. This is because the species of trichinella that typically infects wild game is more resistant to freezing than the species that infects pigs.
- Cooking all meat fed to pigs or other wild animals.
- Keeping pigs in clean pens with floors that can be washed (such as concrete).
- Not allowing hogs to eat uncooked carcasses of other animals, including rats, which may be infected with trichinosis.
- Cleaning meat grinders thoroughly when preparing ground meats.
- Control and destruction of meat containing trichinae, e.g., removal and proper disposal of porcine diaphragms prior to public sale of meat.
The Centers for Disease Control and Prevention
makes the following recommendation: "Curing (salting), drying, smoking, or microwaving meat does not consistently kill infective worms."
However, under controlled commercial food processing conditions some of these methods are considered effective by the United States Department of Agriculture
The United States Department of Agriculture (USDA) and Animal and Plant Health Inspection Service (APHIS) are responsible for the regulations concerning the importation of swine from foreign countries. The Foreign Origin Meat and Meat Products, Swine section covers swine meat (cooked, cured and dried, and fresh). The USDA and APHIS developed the National Trichinae Certification Program. This is a voluntary “pre-harvest” program for U.S. swine producers “that will provide documentation of swine management practices” to reduce the incidence of Trichinella
The CDC reports that 0.013% of U.S. swine is infected with Trichinella
Both cooking and freezing are good ways of killing the parasite. 'Certified' pork is pork that has been frozen 30 days or more, for example.
Again, from Wikipedia, it's life cycle:
The domestic cycle involves humans, pigs, and rodents. Pigs become infected when they eat raw infected meat, especially infected rodents. Humans become infected when they eat raw or undercooked infected pork. After humans ingest the cysts from infected undercooked meat, pepsin and hydrochloric acid help free the larvae in the cysts into the small intestine.
The larvae then migrate to the small intestine and invade the columnar epithelial cells; the process of how the columnar cells are invaded is still unknown. 
In the small intestine, the larvae molt four times before becoming adults. 
Thirty to 34 hours after the cysts were originally ingested, the adults mate and within five days produce larvae. 
The worms can only reproduce for a limited period of time because the immune system will eventually expel them from the small intestine.
Genetic studies with laboratory rats seem to indicate that the host’s genetic make-up can determine the duration of the intestinal phase and that “T-cell dependent antigen is necessary for protection against the intestinal phase of the infection”. 
The larvae then use their piercing mouth part called the “sylet” to pass through the intestinal mucosa and enter the lymphatic vessels and then enter the bloodstream. 
The larvae use the capillaries in striated muscle to arrive at their final destination: the muscle fiber cells.
It is believed that the larvae enter the muscle cells through mechanical means. 
The muscle cell that a larva takes over is referred to as the nurse cell. In just three weeks the larvae induce dramatic changes in the muscle cells. 
For instance, the larvae increase the size of the cell’s nucleus and create a “placenta” like structure around the muscle cell called a circulatory rete. 
How can the larvae induce angiogenesis (formation of new blood vessels) around the muscle cell? It is hypothesized that the larvae's genes activate certain genes of the host’s cell to induce these dramatic changes. 
Because humans do not typically get eaten by other animals “humans are a parasitic dead end.” 
Hope this helps!