5.1:
Infection
Pathogens enter and multiply, destroying cells and causing illness that may develop into disease.
The infection spreads in a cyclic chain.
Pathogens like bacteria, viruses, and parasites—start the chain.
These pathogens live, grow, and multiply in reservoirs, such as humans, animals, and the environment.
The reservoir determines the pathogen's portal of exit. Saliva, feces, and blood are human exits.
The mode of transmission can be direct or indirect.
Physical contacts like kissing, and sexual contact, and droplets like sneezing, coughing, and talking carry the virus directly.
However, mosquitoes or inanimate objects like door handles can spread the disease indirectly.
The pathogen enters a susceptible host through the portal of entry through the respiratory tract or fecal-oral route and multiplies in cells and tissues.
Finally, the host's susceptibility may depend on genetics, specific immunity, and other nonspecific factors that affect infection resistance and pathogenicity.
Notably, the cycle continues unless there is a break in the chain, for example, through infection control and contact tracing.
5.1:
Infection
When a pathogen enters the body and reproduces, it can cause an infection, damage body cells, and cause illness symptoms that eventually lead to disease. Therefore, its prevention requires breaking the chain of infection.
The chain begins with pathogens: bacteria, viruses, fungi, prions, or parasites such as protozoa helminths. These can be present on the skin as transient or resident flora, or they can be acquired from the environment. Identifying and treating the type of infection and applying antimicrobial medications are essential. It is also essential to limit the growth of pathogens in the environment. Outbreaks of infection occur because the pathogen is transmitted to a reservoir, such as a human or animal, either directly or indirectly.
Then through the portal of entry, the pathogen enters a susceptible host; this access allows the pathogen to multiply in tissues. Direct transmission occurs through skin-to-skin contact, kissing, sexual intercourse, and soil or vegetation containing infectious organisms. Indirect transmission occurs through air particles, inanimate objects such as vehicles, or animate environments such as vectors. Indirect transmission is often controlled by hand hygiene, use of personal protective equipment, personal hygiene, first aid, safe removal of catheters and tubes, safe surgical procedures and prevention, and proper sharps disposal.
Finally, the host's susceptibility depends on genetic or constitutional factors, specific immunity, and nonspecific factors that impact an individual's ability to resist infection or restrict pathogenicity. Immunizations, treatment of underlying disease, health insurance, patient education, adequate nutrition, and screening of healthcare staff can reduce the susceptibility.