The three most common are the skin, gastrointestinal tract and respiratory tract
stratum corneum
Portacaval shunting.
Portal or nutritional cirrhosis is the form of the disease most common in the United States
Direct contact
The most common route of entry for hazardous materials is inhalation, closely followed by skin contact.http://wiki.answers.com/What_is_the_most_common_route_of_entry_for_hazardous_materials#ixzz1tCem38SH
The circulatory system.
Actually it's too cold for most pathogens to survive down there.
There many common pathogens. They all are disease causing. Path- means disease + -ogen meaning causing. The list is very long but here you will find many http://www.dnafrequencies.com/dp/human.shtml
The most common source of pathogens that cause surgical site infections is the patient.
the most common method of entry into being a veterinarian is having eight years of college and Advanced degrees pursued by many vets are in the basic sciences, such as anatomy, microbiology, and physiology.
Most commonly, acute bronchitis is caused by viruses. Bacterial causes are numerous, although difficult to prove because many people are colonized with bacterial pathogens in the mouth or oropharynx.The most common suspected bacterial pathogens include Mycoplasma pneumoniae, Chlamydia pneumoniae, Haemophilus influenzae, and Streptococcus pneumonia.
Usually disease can be contracted through air or fluids. Through human to human it is more often airborne than fluid borne.