CHAPTER ONE
                                                          INTRODUCTION
This chapter  reviews in brief, Health Care Associated Infections (HAI), elements required for transmission of infectious agent within a health care setting (chain of infection, sources of infection, susceptible host, mode of transmission, portal of entry and portal of exit), HAI among health-care workers, Universal Precautions (UP), Body Substances Isolation (BSI) and Standard Precautions (SP).
1.1 HEALTH CARE- ASSOCIATED INFECTIONS (HAI):
Health-care associated infection (HAI), also referred to as nosocomial infection and hospital acquired infection, is defined by Center of Disease Control and Prevention (CDC) as an “infection caused by a wide variety of common and unusual bacteria, fungi, and viruses during the course of receiving medical care”(CDC, 2012). It either occurs while patients receive care or may develop after discharge. It also involves occupation infection among staff. HAI can also be defined as an “infection occurring in patients during the process of care in a hospital or health care facility which was not present or incubating at the time of admission. This includes infection acquired in the hospital, but appearing after discharge and also occupational infections among staff or facility” (WHO, 2012).HAI is considered an important public health problem (WHO, 2012). Globally, hundreds of millions of patients are infected by HAI every year in both developed and developing countries. According to WHO, its prevalence in developed countries varied between 3.5% and 12%, while in developing countries it varied between 5.7% and 19.1% (WHO, 2012). The highest occurrence of HAI were in acute surgical, orthopedic wards and Intensive Care Unit (WHO, 2002). The prevalence rate of ICU-acquired infection in high-income countries was 30%, while in middle and low-income countries, it was at least 2-3 times higher than that in high -income countries(WHO, 2009; WHO, 2012).
The consequences of HAI at patients’ level imply more suffering, more complications, more treatments, and increase in hospitalization periods. For example, in Europe duration of hospitalization increased to nearly 16 million extra days (WHO, 2012).This is in itself considered a risk factor for acquiring HAI, and it means an increase in costs (WHO, 2012). In addition, it increases economic burden on the health care systems of countries. For example, in England, the annual financial costs topped 1.3 billion euro’s, while in the United States of America, the costs amounted to approximately 3.5 billion euro’s and 7 billion euro’s in Europe (WHO, 2012; WHO, 2012; Agozzino et al., 2012).
1.2 HEALTH-ASSOCIATED INFECTIONS AMONG HEALTH CARE WORKERS NURSES:
HAI  can  affect  both  patients  and  health-care  workers. It   involves  Occupational  infections among nurses. Due to  the  nature  of  their occupations, the major occupational hazard is the transmission of blood-borne disease such as hepatitis B and AIDS by being exposed to injuries caused by contaminated sharp objects such as scalpels and broken glass and needle stick (CDC, 2012). Nurses can be infected by HAIs while dealing with patients or providing them with health treatment. They can play a role in the widespread of infections. For example, the nurses played an important role in the amplification of the outbreak of Marburg viral hemorrhage fever in Angola (WHO, 2015). The mode of transmission depends on many factors such as immunity of HCW and amount of blood transferred during injuries (CDC, 2012). According to WHO, nearly three million HCW are exposed to percutaneous blood borne pathogens each year worldwide; 2 million of those were exposed to HBV ,0.9 million to HCV and 170, 000 to HIV. These sharp injuries resulted in 15,000 HCV, 70,000 HBV and 500 HIV infections. About 90% of these events happened in the developing countries (WHO, 2014). The infectious agent is transmitted to nurses mainly via droplet: direct contact or contact with inanimate contaminated objects by infectious material. The risk of transmission of infectious agents would increase if infection control practice and standard precautions were not applied (WHO, 2013).