| Throughout history man has faced the spread of | | | | transmission: contact, droplet, airborne, vehicle, and |
| infection, pondering its causes and how to treat it or | | | | vector. The same microbe can be transmitted by |
| prevent it. Infections have been known to affect | | | | more than one route. |
| major segments of the population, as did the plague | | | | Contact transmission |
| in the Middle Ages. Although important advances | | | | Contact transmission is the most frequent mode of |
| have been made in understanding and treating | | | | infection transmission. There are two types of |
| infection, the threat of infection looms as large as it | | | | contact transmission, direct transmission and indirect |
| ever has. Newer enemies in the battle of infection | | | | transmission. |
| emerge such as HIV and hepatitis C virus (HCV). | | | | Direct contact transmission involves direct, physical |
| Once-conquered enemies become resistant to | | | | transfer of a pathogenic microbe to a susceptible |
| treatment, as it the case of Mycobacterium | | | | host through close or intimate contact such as |
| tuberculosis and methicillin-resistant Staphylococcus | | | | touching or kissing. |
| aureus. Healthcare personnel typically encounter | | | | Indirect contact transmission involves personal |
| numerous patients on a daily basis, many of whom | | | | contact by a susceptible host with contaminated |
| may be harboring these or other agents of infection. | | | | inanimate objects such as patient bed linens, clothing, |
| Measures to prevent the spread of infection must be | | | | dressings, and eating utensils. It includes contact with |
| taken in the course of treating all patients. | | | | phlebotomy equipment such as gloves, needles, |
| Below we explain the infection process and describe | | | | specimen tubes, and phlebotomy carts and trays. It |
| infection control measures needed to protect | | | | also includes less obvious contaminated objects such |
| healthcare patients, staff, visitors, and those who do | | | | as doorknobs and faucet handles. The transfer of |
| business with healthcare facilities. | | | | infectious microbes from contaminated hands to a |
| What Is Infection? | | | | susceptible host is also considered indirect contact |
| Our environment is full of microorganisms | | | | transmission. |
| (microscopic organisms) referred to as microbes. | | | | Droplet transmission |
| Microbes include bacteria, fungi, protozoa, and viruses. | | | | Droplet transmission involves the transfer of the |
| The majority of microbes are nonpathogenic, | | | | infective microbe to the mucous membranes of the |
| meaning they do not cause disease under normal | | | | nose or mouth or the conjunctiva (mucous |
| conditions. Microbes that are capable of causing | | | | membranes) of the eyes of a susceptible individual |
| disease (ie., pathogenic) are called pathogens. If a | | | | through sneezing, coughing, or talking by an infected |
| pathogen invades the body and the conditions are | | | | per- son. Droplet transmission can also occur during |
| favorable for it to multiply and cause injurious effects | | | | procedures such as suctioning and throat swab |
| or disease, the resulting condition is called an infection. | | | | collection. It differs from airborne transmission in that |
| The pathogen responsible for causing the infection is | | | | droplets do not travel more than 3 feet, and do not |
| referred to as the infectious or causative agent. | | | | remain suspended in air. |
| Infection can be local (restricted to a small area of | | | | Airborne transmission |
| the, body) or systemic, in which the entire body is | | | | Airborne transmission involves dissemination of |
| affected. | | | | droplet nuclei. Droplet nuclei are the residue of |
| Communicable Infections | | | | evaporated droplets generated by sneezing, |
| Some pathogenic microbes cause infections that can | | | | coughing, or talking. Infectious microbes within droplet |
| be spread from person to person. These infections | | | | nuclei can remain viable even though suspended in |
| are called communicable infections and the diseases | | | | the air or in dust particles for long periods. Microbes |
| that result are called communicable diseases. A | | | | carried in this manner can become widely dispersed |
| division of the U.S. Public Health Service called the | | | | before being inhaled by or deposited on a susceptible |
| Centers for Disease Control and Prevention (CDC) is | | | | host. For this reason, special air handling and |
| charged with the investigation and control of various | | | | ventilation are required for rooms of patients having |
| diseases, especially those that are communicable and | | | | infections with airborne transmission. Persons entering |
| have epidemic potential. The CDC recommends | | | | the room must wear a snug-fitting mask with a |
| safety precautions to protect healthcare workers | | | | special filter. M. tuberculosis, rubeola virus, and varicella |
| and others from infection. | | | | virus are the most common microorganisms |
| Nosocomial Infections | | | | transmitted by the airborne route. |
| Approximately 5 % of patients in the United States | | | | Vector transmission |
| are exposed to and contract some sort of infection | | | | Vector transmission involves the transfer of the |
| after admission to a hospital or other healthcare | | | | microbe by an insect, arthropod, or animal. An |
| facility. These hospital or healthcare facility-acquired | | | | example of vector transmission is the transmission of |
| infections are called nosocomial infections. Nosocomial | | | | malaria by a mosquito or the plague by rodent fleas. |
| infections can result from contact with infected | | | | Vehicle transmission |
| personnel, other patients, and visitors, or | | | | Vehicle transmission involves the transmission of the |
| contaminated equipment. The most common | | | | infective microbe through contaminated food, water, |
| nosocomial infection in the United States is urinary | | | | or drugs. Examples of vehicle transmission are |
| tract infection. The Hospital Infection Control Practice | | | | salmonella infection from handling contaminated |
| Advisory Committee (HICPAC), established in 1991, | | | | chicken and shigella infection from drinking |
| advises the CDC on updating guidelines regarding | | | | contaminated water. The transmission of hepatitis |
| prevention of nosocomial infection. | | | | and HIV through blood transfusion is also considered |
| Source Of Infection | | | | vehicle transmission. |
| The source is the origin of infectious microorganisms, | | | | Susceptible Host |
| also called the reservoir. Sources of infectious | | | | A susceptible host is someone who has decreased |
| microbes include infected humans or anima1s and | | | | ability to resist infection. Susceptibility is affected by |
| contaminated articles and equipment. In a healthcare | | | | age, health, and the immune status of the individual. |
| setting, human sources of infectious microbes can be | | | | For example, newborns whose immune systems are |
| patients, personnel, or visitors, and can include those | | | | not yet developed and old people whose immune |
| with active disease, those whose disease is in the | | | | systems are no longer functioning properly are more |
| incubation period, and those who are chronic carriers | | | | susceptible to infections. In addition, disease, antibiotic |
| of a dis- ease. Another potential source of infectious | | | | treatment, and immunosuppressive drugs may |
| microbes is a person's own normal flora | | | | compromise a person's resistance to infection. |
| (microorganisms that normally live on the skin and | | | | Procedures such as surgery, anesthesia, and insertion |
| other areas of the human body). | | | | of catheters can also leave a patient more |
| Inanimate objects such as contaminated equipment | | | | susceptible to infection. Recovery from a particular |
| can be a major source of infection in a healthcare | | | | virus or vaccination against a virus also affects |
| setting. Whether or not an inanimate source is | | | | susceptibility. A healthy person who has received a |
| capable of transmitting infection depends upon the | | | | vaccination against a disease-causing virus, or who |
| amount of contamination, the viability or ability of the | | | | has recovered from infection with a particular virus, |
| organism to survive on the source, the virulence or | | | | has developed antibodies against that virus and is |
| degree to which an organism is capable of causing | | | | considered to be immune, or unlikely to develop the |
| disease, and the amount of time elapsed between | | | | disease. |
| when the source was contaminated and when it was | | | | Breaking The Chain Of Infection |
| contacted. | | | | Breaking the chain of infection means stopping |
| For example, the virus that causes hepatitis B is | | | | infections at the source, eliminating means of |
| much more virulent, or capable of causing disease | | | | transmission, and reducing or eliminating the |
| from a small amount of infective material, than HIV, | | | | susceptibility of potential hosts. Ways to prevent |
| the virus that causes AIDS. It is also more viable, | | | | transmission of infectious microbes are proper hand |
| meaning it is capable of surviving longer on surfaces | | | | washing; use of gloves, gowns, masks, and other |
| than is HIV. However, if a long enough time elapses | | | | protective equipment when indicated; proper waste |
| from the time of contamination until contact by a | | | | disposal; isolation procedures; insect and rodent |
| susceptible host, the microbe is no longer alive and is | | | | control; and decontamination of surfaces and |
| not capable of transmitting disease. | | | | instruments. Susceptibility of potential hosts can be |
| Modes Of Transmission | | | | reduced through proper nutrition, reduction of stress, |
| There are five basic modes or routes of infection | | | | and immunization against common pathogens. |