<P> Another effective way to decrease the transmission rate of infectious diseases is to recognize the effects of small - world networks . In epidemics, there are often extensive interactions within hubs or groups of infected individuals and other interactions within discrete hubs of susceptible individuals . Despite the low interaction between discrete hubs, the disease can jump to and spread in a susceptible hub via a single or few interactions with an infected hub . Thus, infection rates in small - world networks can be reduced somewhat if interactions between individuals within infected hubs are eliminated (Figure 1). However, infection rates can be drastically reduced if the main focus is on the prevention of transmission jumps between hubs . The use of needle exchange programs in areas with a high density of drug users with HIV is an example of the successful implementation of this treatment method . Another example is the use of ring culling or vaccination of potentially susceptible livestock in adjacent farms to prevent the spread of the foot - and - mouth virus in 2001 . </P> <P> A general method to prevent transmission of vector - borne pathogens is pest control . </P> <P> Infection with most pathogens does not result in death of the host and the offending organism is ultimately cleared after the symptoms of the disease have waned . This process requires immune mechanisms to kill or inactivate the inoculum of the pathogen . Specific acquired immunity against infectious diseases may be mediated by antibodies and / or T lymphocytes . Immunity mediated by these two factors may be manifested by: </P> <Ul> <Li> a direct effect upon a pathogen, such as antibody - initiated complement - dependent bacteriolysis, opsonoization, phagocytosis and killing, as occurs for some bacteria, </Li> <Li> neutralization of viruses so that these organisms cannot enter cells, </Li> <Li> or by T lymphocytes, which will kill a cell parasitized by a microorganism . </Li> </Ul>

Describe the process of infection by a viral pathogen