Infection via the skin:
- Intact skin has a tough outer layer of cornified cells. This barrier protects the body from most virus, but it is frequently breached by an insect bite. Some viruses can enter via hair follicles, sweat glands, cuts as well as bruises.
Infection via the mucuous membranes:
- Respiratory tract is by far the most common route of viral infection. viruses may initiate infection if they attach to celss of respiratoty tract, they are also transferred by contact with contaminated fingers. It will eventually cause colds and pneumonia.
- In the stomach, although it is potentially exposed to a great number and variety of viruses, the tough condition has protect it from many viruses. For example, viruses that have a lipid-containing envelope are usually inactivated by the acid, bile salt and enzymes that occur in the stomach.
- Viruses can infect human through sexually tansmission, the most common virus is HIV (Human Imunodeficiency Virus).
- A few viruses are shed in the urine of humans which may cause human disease as a result of the inhalation of dust containing virus particles.
- Viruses of several families occasionally infect the conjunctiva directly through the bloodstream.
Infection via placenta:
- Viruses can cross placenta and infect the foetus as it is the only route which the mother connect to the baby. This infection may cause the results such as spontaneous abortion, birth defect and premature birth.
Infection via parenteral route:
- Viruses are deposited via punctures, they contacts pathways to enter the body though bites, cuts, stab wounds or surgery to the blood and periheral nerves. The most common route of systemic spread of virus involves the circulation.
- Viruses can enter the body through the neves as well, but is less common than bloodstream dissemination.
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