In the United States, at the beginning of the twentieth century, infectious diseases were the leading cause of death. By 2000 improvements in nutrition and sanitation, the discovery of antibiotics, and the development of vaccines had put an end to infectious disease epidemics like diphtheria and typhoid fever that once ravaged entire populations. In 1900 respiratory and diarrheal diseases were major killers. For example, TB led to over 11% of all deaths in the United States and was the second leading cause of death; by the early twenty-first century, only 0.02% of all deaths were attributed to this once frequently fatal disease (CDC, 2009a). As individuals live longer, chronic diseases—heart disease, cancer, and stroke—have replaced infectious diseases as the leading causes of death.

Infectious diseases, however, have by no means vanished, and they remain a continuing cause for concern. They persist as the third-leading cause of death in the United States and the second-leading cause worldwide, where they are responsible for killing an estimated 15 million people a year (Fauci, Touchette, and Folkers, 2005). In the United States, the downward trend in mortality from infectious diseases, seen since 1900—with the exception of the 1918 influenza pandemic—reversed itself in the 1980s, with the emergence of new entities such as HIV disease and the increasing development of antibiotic resistance. Respiratory diseases in the form of pneumonias and influenza remain among the 10 leading causes of death, and new strains such as novel influenza A H1N1 and avian influenza A H5N1 test our disease control abilities and consume resources. Previously unknown causal connections between infectious organisms and chronic diseases have been recognized, such as Helicobacter pylori and peptic ulcer disease, and human papillomaviruses (HPVs) and cervical cancer. Also, in the twenty-first century, infectious diseases have become a means of terrorism, as illustrated by the anthrax letters of 2001.

New killers emerge and old familiar diseases take on different, more virulent characteristics. Consider the following developments from the past 30 years. HIV disease reminds us of plagues from the past and challenges our ability to control and contain infection like no other disease in recent history. Because drugs have been developed to slow the progression but there is still neither vaccine nor cure, this initially infectious disease is now a chronic condition as well. Legionnaires’ disease and toxic shock syndrome, unknown at mid-twentieth century, have become part of common vocabulary. The identification of infectious agents causing Lyme disease and ehrlichiosis provided two new tickborne diseases to worry about. And, in the summer of 1993 in the southwestern United States, healthy young adults were stricken with a mysterious and unknown but often fatal respiratory disease that is now known as hantavirus pulmonary syndrome. The summer of 1994 brought public attention to a severe, invasive strain of Streptococcus pyogenes group A, referred to by the press as the “flesh-eating” bacteria.

In the 1990s the transmission of infectious disease through the food supply became a newsworthy concern when the consumption of improperly cooked hamburgers and unpasteurized apple juice contaminated with a highly toxic strain of E. coli (E. coli 0157:H7) caused illness and death in children across the country. In 1996 multiple states reported outbreaks of diarrheal disease traced to imported fresh berries; the implicated organism in these outbreaks, Cyclospora cayetanensis (a coccidian parasite), was only first diagnosed in humans in 1977. Also in 1996, the fear that “mad cow disease” (bovine spongiform encephalopathy [BSE]) could be transferred to humans through beef consumption led to the slaughter of thousands of British cattle and a ban on the international sale of British beef. Initially seen only in Europe and Japan as well as Great Britain, the first case of BSE was diagnosed in the United States in 2003. Variant Creutzfeldt-Jakob disease (vCJD), which attacks the brain with fatal results, is the human disease hypothesized but not yet proven to result from eating beef infected with the transmissible agent causing BSE; only three acquired cases of vCJD have been seen in the United States, but these individuals were born outside of and resided in the country for only a short period (CDC, 2009b).

In 1997 vancomycin-resistant Staphylococcus aureus (VRSA) was first reported; previously, vancomycin had been considered the only effective antibiotic against methicillin-resistant S. aureus (MRSA). Although MRSA is still largely a hospital-acquired infection, community-associated disease is becoming more common with outbreaks frequently associated with school athletic programs and prison populations. Also in 1997, the first reported outbreak of avian flu affecting humans occurred in Hong Kong. No subsequent reports suggested an isolated incident, but in 2004, avian influenza A H5N1 again emerged in Southeast Asia with resulting human cases. This virus has now infected avian populations in Asia, Europe, the Near East, and North Africa, and it continues to cause sporadic human cases, especially in Southeast Asia and Egypt. Human cases are determined to largely spread through direct contact with infected poultry or infected surfaces, with human to human transmission largely ineffective and only a few rare cases thought to have occurred. In 1999 the first western hemisphere activity of West Nile virus (WNV), a mosquito-transmitted illness that can affect livestock, birds, and humans, occurred in New York City. By 2002 WNV, thought to be carried by infected birds and possibly mosquitoes in cargo containers, had spread across the United States as far west as California and was reported in Canada and Central America as well.

The viral hemorrhagic fevers Ebola and Marburg, unknown to most people 30 years ago, have become the premise of movies and books. Although caused by different viruses within the Filoviridae family, these sporadically occurring but lethal killers have similar clinical presentations. The most recent large outbreaks of Ebola have been in 2007 in the Democratic Republic of the Congo (249 cases, 183 deaths) and in Uganda (149 cases, 37 deaths). Marburg virus had only been reported five times since its recognition in 1967 before a major outbreak in Angola occurred during 2004 and 2005, affecting more than 350 people with a fatality rate of close to 90%. Since then, a much smaller outbreak occurred in Uganda in 2007 among gold miners. The source for both of these viruses is still undetermined, but there is an association with non-human primates, and evidence is also beginning to point toward a bat reservoir (Heymann, 2008).

Severe acute respiratory syndrome (SARS) was first recognized in China in February 2003. And as if in a bestselling thriller, this newly emerging infectious disease quickly achieved pandemic proportions. By the summer of 2003, major outbreaks had occurred in Hong Kong, Taiwan, Vietnam, Singapore, and Canada. Three months after the first official news of SARS, over 8000 cases with more than 700 deaths had been reported to the World Health Organization (WHO) from 28 countries. Played out on television in pictures of people wearing face masks for protection, the rapid spread of a previously unknown disease with an initially unknown cause and no definitive treatment contributed to the creation of a perception of risk of infection far greater than actually existed. Frightened Americans canceled trips to China and Hong Kong and avoided people who had recently returned from Asia. Then, as suddenly as it began, the pandemic subsided. SARS was eventually determined to be caused by a new strain of Coronavirus, but since 2003, only a few cases, largely associated with laboratory workers, have been reported. A large number of individuals infected by SARS could be traced back to unrecognized cases in hospitals, suggesting that prompt identification and isolation of symptomatic people is the key to interrupting transmission. Global efforts continue to clarify the epidemiology of this disease as well as develop a reliable diagnostic test and vaccine. Additional information on SARS can be obtained at the WHO Global Alert and Response website (http://www.who.int/csr/sars/).

In the first decade of the twenty-first century, foodborne infections again have made headlines as E. coli–infected spinach sickened and killed individuals across the United States. In 2008, tomatoes were blamed for a nation-wide outbreak of salmonellosis but were ruled innocent when the green chilies that accompanied them in salsa were found to be the actual culprit. Salmonella again made the news as contaminated peanut butter forced recalls across the United States, sickened hundreds, and resulted in several deaths. Even chocolate chip cookie dough was not safe; a national recall in 2009 followed the discovery that people had been sickened after eating raw dough contaminated by E. coli. Perhaps the most publicized infectious disease event of 2009 was the advent of a new strain of flu, novel influenza A H1N1. First reported from Mexico and rapidly acquired by travelers to that country, H1N1 spread quickly across the world, causing the WHO to declare a pandemic and stimulate the race for a vaccine.

Worldwide, infectious diseases are the leading killer of children and young adults and are responsible for almost half of all deaths in developing countries. Of these infectious disease deaths, 90% result from six causes: acute respiratory infections, diarrheal diseases, malaria and measles among children; and TB and HIV infection among adults. Malaria alone is estimated to kill 1.2 million people a year and TB another 1.7 million (or over 4600 people per day) (Heymann, 2008). The CDC in its Ounce of Prevention campaign notes that in the United States as many as 160,000 people die per year with infectious diseases as an underlying cause. The economic burden of infectious diseases is staggering. In the United States, the USDA Economic Research Service estimated the cost of foodborne illnesses caused by just two organisms—salmonella and E. coli 0157:H7—at over $3 billion in 2008 dollars (USDA, 2009). The Produce Safety Project at Georgetown University in 2010 suggested that the total cost from foodborne illness could be more than $152 billion (Pew Charitable Trusts, 2010). CDC researchers determined that in the United States in 2000, nine million cases of sexually transmitted infections occurred among young people 15 to 24 years of age with a total estimated cost of $6.5 billion, with HIV disease and HPV accounting for 90% of the total burden (Chesson et al, 2004). Hospital-acquired infections are estimated to have killed 48,000 people and cost $8.1 billion to treat in 2006 (Eber et al, 2010).

Because of the morbidity, mortality, and associated cost of infectious diseases, the national health promotion and disease prevention goals outlined in Healthy People 2020 list a number of objectives for reducing the incidence of these illnesses in the section on Immunization & Infectious Disease (see the Healthy People 2020 box). Objectives for reducing salmonellosis and other foodborne infections are found in the section on Food Safety and an objective for reducing malaria cases reported in the United States may be seen under Global Health. Although infectious diseases are not currently the leading causes of death in the United States, they continue to present varied, multiple and complex challenges to all health care providers. Nurses must know about these diseases to effectively participate in diagnosis, treatment, prevention, and control.

During the first half of the twentieth century, the weekly publication of national morbidity statistics by the U.S. Surgeon General’s Office was accompanied by the statement, “No health department, state or local, can effectively prevent or control disease without knowledge of when, where, and under what conditions cases are occurring” (CDC, 1996a, p 531). Surveillance gathers the “who, when, where, and what”; these elements are then used to answer “why.” A good surveillance system systematically collects, organizes, and analyzes current, accurate, and complete data for a defined disease condition. The resulting information is promptly released to those who need it for effective planning, implementation, and evaluation of disease prevention and control programs.

Communicable disease can be prevented and controlled. The goal of prevention and control programs is to reduce the prevalence of a disease to a level at which it no longer poses a major public health problem. In some cases, diseases may even be eliminated or eradicated. The goal of elimination is to remove a disease from a large geographic area such as a country or region of the world. Eradication is removing a disease worldwide by ending all transmission of infection through the complete extermination of the infectious agent. WHO officially declared the global eradication of smallpox on May 8, 1980 (Evans, 1985). After the successful eradication of smallpox, the eradication of other communicable diseases became a realistic challenge, and in 1987 WHO adopted resolutions for eradication of paralytic poliomyelitis and dracunculiasis (guinea worm infection) from the world by the year 2000.

These eradication goals were not reached in 2000, but substantial progress has been made. When the resolution was made in 1987 for the eradication of Guinea worm disease, there were an estimated 3.5 million cases a year in 20 countries in Asia and Africa and 120 million people were at risk for the disease. By the end of 2007 the disease was endemic only in five countries in Africa and less than 10,000 cases were reported. Of the cases occurring during the first half of 2008, 98% were reported from Sudan, Ghana, and Mali. Sporadic violence appears to be the challenge to successful eradication of endemic dracunculiasis in this region of Africa (CDC, 2008a).

By 2010 the number of polio-endemic countries had decreased from 125 to 4 (Afghanistan, India, Nigeria, and Pakistan); 1256 cases of non–vaccine-derived or wild-type polio virus were reported from these four polio-endemic countries in 2009, compared with 350,000 cases reported from those 125 countries in 1988; another 350 imported cases from 10 non-endemic countries were also reported. Importation of cases resulting from the ease of worldwide travel or breakdowns in coverage in a neighboring country has led to outbreaks in non-endemic countries several times in the last 10 years, the largest being spillover into adjacent countries from Nigeria beginning in 2003 and cases in far-flung countries originating from exposure during the Muslim religious pilgrimage to Mecca. Such outbreaks point to the necessity of maintaining mass vaccination campaigns in polio-free countries to protect against cases imported from endemic areas. Challenges to eradication include political instability and sporadic violence, cultural beliefs about immunization, religious fears, and distrust of immunization (CDC, 2009d).

The Americas were certified polio free in 1994 (an outbreak in Haiti and the Dominican Republic in 2000 was vaccine derived), with the western Pacific certified in 2000 and Europe in 2002 (WHO, 2002). April 2005 marked the fiftieth anniversary of the polio vaccine. In 2004 WHO released an updated Global Polio Eradication Initiative Strategic Plan, outlining activities required to: (1) interrupt global polio transmission, (2) achieve global polio eradication certification, and (3) prepare for global cessation of childhood vaccination with the oral poliovirus vaccine (CDC, 2004). With the Global Polio Eradication Initiative, WHO partnered with national governments, Rotary International, the CDC and UNICEF in what has been called the largest public health initiative the world has ever known. Since 1988, over 2 billion children around the world have been immunized against polio through the cooperation of more than 200 countries and 20 million volunteers, supported by an international investment of over $3 billion. At the end of 2008, WHO reviewed the progress of the initiative with two independent outside agencies and concluded that the remaining technical and operational challenges to eradication could be overcome in each of the polio-endemic countries by ensuring the political commitment of all polio-affected countries to attain the highest possible coverage and enhancing routine vaccination and surveillance (CDC, 2009d). (Read more about global polio eradication efforts at http://www.polioeradication.org/.)

Primary, Secondary, and Tertiary Prevention

There are three levels of prevention in public health: primary, secondary, and tertiary. In prevention and control of infectious disease, primary prevention seeks to reduce the incidence of disease by preventing occurrence, and this effort is often assisted by the government. Many interventions at the primary level, such as federally supplied vaccines and “no shots, no school” immunization laws, are population based because of public health mandate. Nurses deliver childhood immunizations in public and community health settings, check immunization records in daycare facilities, and monitor immunization records in schools.

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Refusal of preventive health care to undocumented residents may prove a threat to the public’s health.

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