Читать книгу Basic Virology - Martinez J. Hewlett - Страница 42

A significant number of human viruses leading to either mild or life‐threatening disease are maintained solely in human populations. The list runs the gamut from colds caused mainly by rhinoviruses, warts caused by papillomaviruses, to AIDS caused by HIV. The mode of passage of viruses between humans (i.e., the vector) is intimately linked to human behavior. This behavior can be modified by the disease symptoms themselves. Thus, a respiratory infection leads to irritation of the airways resulting in coughing and sneezing, which spreads an aerosol of droplets containing virus. Herpes simplex virus 1 (HSV‐1) is spread in saliva resulting in transfer of the virus to the recipient's oral epithelial cells; in contrast, the closely related varicella zoster virus (VZV, or chickenpox) is spread by inhalation of a virus‐loaded aerosol or dust containing dead skin flakes. Warts are spread by direct physical contact between the virus‐loaded source (another wart or dead skin from a wart) and layers of the skin below the keratinized epidermis exposed by small cuts or abrasions. Poliovirus and the related coxsackieviruses are spread by virus‐containing feces contaminating food, drinks, or fomites that are ingested; this is termed oral‐fecal spread. In the case of HIV, body fluids – including blood, breast milk, serum, vaginal secretions, and seminal fluid – are sources of infection. The virus can be spread by passive inoculation of, for example, a contaminated hypodermic syringe, or by transfusion, breastfeeding, or sexual activity.

Table 3.1 Some pathogenic viruses, their vectors or routes of spread, and their hosts.