Identifying the Problem: Infectious Diseases and Consequences
Historically, prevention of infectious diseases provided one of the cornerstones of public health. Many of the approaches that the public health community uses to tackle ongoing problems stem from the policies used to deal with major infectious-disease challenges in the late 19th and early 20th century. These include careful epidemiology, interventions grounded in scientific understanding of causality, sound public policy, and strong public support based on clear messaging and a public understanding of the benefit of prevention.
It is important to note, however, that in spite of many significant advances, infectious diseases still account for about one quarter of annual deaths worldwide.1 (Table 10.1). The burden of these diseases varies greatly by geography, with the greatest impact being seen in low-income countries. Although the Western world, including the United States is much less affected by the infectious diseases of childhood (such as pneumonia, diarrhea, and malaria), it remains vulnerable to and affected by emerging infections and other infectious-disease problems, and these continue to present significant challenges to the developed world.
Table 10.1 Major Causes of Global Premature Death: 2010
Major Causes of Premature Death: 2010
Ischemic Heart Disease
Lower Respiratory Infections*
Preterm Birth Complications
Chronic Obstructive Pulmonary Disease (COPD)
* = infectious disease.
Adapted from: Lozano R, Naghavi M, Foreman K, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012;380:2095–2128.
In the United States, chronic viral infections, such as HIV2 and hepatitis B and C3, are readily transmitted and contribute to ongoing morbidity. Outbreaks of food-borne infections are extremely common with both health and economic consequences. Health-care associated infections have been identified as an important preventable cause of death in modern health care. Outbreaks of vaccine-preventable infections have increasingly been seen, reflecting public complacency, misinformation (sometimes deliberate), and, in some communities, distrust of government.
Increasing global connectivity is a reason why antimicrobial resistance has now become a global public health crisis, whose solution will require multinational, transdisciplinary, and policy approaches. The world as a whole is also vulnerable to changes in vector-borne and zoonotic infections, which often reflect changes in land use (whereby humans come into contact with previously un-encountered animal pathogens) and/or changes in climate (which facilitates survival of vectors of infection). In these cases, the increasing connectivity of the world with rapid and global transportation enhances the risk of localized infections becoming pandemic problems. The recent outbreak of Ebola virus infection in West Africa provides an object lesson in global vulnerability.4 Infection, caused by a filovirus, is a zoonosis where the primary host is probably a fruit bat. Incidental contact between humans and the mammalian host led to slow but progressive transmission among humans—with lethal effect. Spread of the epidemic was facilitated by the fact that the initial infection occurred in a part of the world where there has been significant breakdown of public governance (after many years of civil war) and where public health infrastructure was essentially nonexistent. Increasing urbanization in resource-poor countries also added to more rapid transmission of this virus than had been seen in many prior outbreak situations.
Prevention policy as it pertains to infectious diseases has a long history; one which has brought together the clinical, research, and public health communities to develop policies that have been implemented at local, state, and national levels. A prevention policy strategy can be planned for virtually every infectious disease, given that prevention usually means disrupting transmission from an affected individual or source to other vulnerable individuals (or communities). Appropriate and scientifically based prevention policy approaches for infectious disease must involve an understanding of pathogenesis and transmission dynamics and must be designed to address the multifactorial aspect inherent to this topic. Specifically, infectious disease prevention policy must include the following components: tracking methods, transmission and control protocols, prevention strategies, and treatment regimens.
Public policy is driven in part by public attitudes, which, in turn, affect policy makers’ readiness to take action. Public acceptance of approaches to prevent and control infectious diseases is generally high, in spite of the fact that the laws and regulations that underpin these approaches generally involve some invasion of privacy and personal rights. Control and prevention of infectious diseases can involve mandatory reporting of cases (with identification of individuals) to public authorities, tracing of contacts (with attendant loss of privacy and occasional embarrassment and/or public disclosure), compulsory quarantine, mandatory treatment, mandatory vaccination, and in some extreme cases even incarceration. Pets or other animals that are regarded as potential sources of human infection can be seized, quarantined, and even destroyed. Businesses, such as restaurants, can be closed. In all of these scenarios, there has been little or no public debate as to the appropriateness of the public health measures. This may reflect a general acceptance of the reasons for these measures; although in many cases it also may reflect the general fear (whether reasonable or groundless) that the public has regarding contagious diseases. It is perhaps striking to observe that the area in which we have had the greatest effect in controlling infection, (i.e., vaccination), has become an area in which there is now greater public skepticism and debate. In addition, there are newer areas of infectious disease, where new and different strategies may need to be adopted, which will offer new challenges and opportunities in terms of public health policy.
Importance of Tracking Infectious Diseases
A critical need exists for communities at all levels to have the capacity to track infections and identify potential outbreaks. This requires appropriate epidemiologic infrastructure that collects data on important communicable diseases, has the ability to analyze such data to identify outbreaks or potential sources of new infection, and has the capacity to intervene where appropriate. Policies in which processes and resources for tracking are outlined are extremely important. Examples of infectious diseases where such data gathering is critical in prevention include sexually transmissible infections (e.g., HIV), hospital-associated infections, tuberculosis, and foodborne illnesses. Tracking and data gathering are also vital in understanding emerging infectious diseases that might have pandemic potential. (See Box 10.1.) In ideal circumstances, this infrastructure should have a local focus, but also should be linked into state and national public health structures so that emerging outbreaks that have epidemic or pandemic potential can be rapidly identified and effective prevention policy solutions determined.
The role of surveillance and identification of possible infections is so critical to public health that most states (and/or other jurisdictions) have a list of reportable infectious diseases, the incidence of which must be reported to the local or state public health department. Box 10.2 illustrates some of the infections that require mandatory reporting to the Missouri Department of Health and Senior Services. Full details of all the many reporting requirements can be found online8. Reporting requirements vary depending on the seriousness of the infection and the urgency with which a public health response must be deployed. The onus for such reporting falls on diagnostic laboratories, individual physicians, or others; and, the penalties for failing to report can be significant.
* This box represents a sample of diseases and conditions reportable in Missouri to local health agencies or to the Missouri Department of Health and Senior Services. A full list of reportable diseases and conditions can be found at http://health.mo.gov/living/healthcondiseases/communicable/communicabledisease/pdf/reportablediseaselist1.pdf
Preventing Transmission of Infectious Diseases
Having identified potential infectious diseases that threaten public health, prevention policies must then address control measures that interrupt transmission. The type of intervention needed will depend on the mode of transmission of the infection. For vector-borne disease, attempts to control vectors (i.e., use of insecticides and control of stagnant water) are important public-health measures, especially in resource-poor settings. However, vector control also remains important in the United States, as mosquito-borne infections have increased in importance over the last 15 years. This was first noted with the arrival of West Nile virus in the early part of the 21st century.9 Dengue fever10 and Chikungunya fever11 are moving into the southern United States from the Caribbean and Central America. Prevention of acquisition (by preventing insect bites in particular) is also an important public health strategy. These strategies include wide-scale provision of bed netting, as well as the use of medication to prevent parasites from establishing infection when individuals are bitten by the vector, such as malaria prophylaxis for travel to endemic areas. Prevention of tick bites is also important in parts of the United States, where tick-borne illnesses such as New England and Lyme disease are prevalent.12
For significant zoonotic infections, policy prevention approaches largely involve coordination with animal control regulations. For example, to prevent rabies in both domestic animals and incidental human transmission, most jurisdictions have developed laws or regulations to require rabies vaccination for dogs, with penalties for those who do not comply. For countries such as the United Kingdom or Ireland where rabies is not endemic in local animals, these regulations have been extended to require either evidence of immunity or quarantine for up to six months before dogs can be imported.
Prevention of food-borne infections is another area where prevention policies overlap with regulations governing other industries (i.e., agriculture and food). Most food-borne outbreaks are local, making local and state epidemiology critical in identifying such outbreaks. Epidemiologic investigation may identify a source, which would then necessitate involvement of other regulators (e.g., those involved in licensing restaurants) to determine whether breaches in existing laws and regulations have occurred. However, with the industrialization and centralization of food production and supply, multistate and multinational outbreaks have become more frequent. By necessity, investigation of such outbreaks involves agencies with broader remits, such as the U.S. Centers for Disease Control and Prevention (CDC), state health departments, the Food and Drug Administration (FDA), and the U.S. Department of Agriculture, along with equivalent regulators in Europe and elsewhere. This has led to stronger regulations in the United States, such as efforts by the FDA to regulate egg safety in order to better control Salmonella contamination, and efforts by the CDC to increase population-based surveillance of common food-borne pathogens.
Serious infections that involve human-to-human transmission require prevention policies based on the risk and timing of acquisition of infection by vulnerable hosts. A very important public health strategy, which often requires the law to enforce it, is quarantine. Although quarantine is often raised as an emotive public response to new or emerging infections (especially those with lethal consequences), it is only an effective public health strategy when individuals with infection can be identified before they become contagious, and, therefore, have the ability to infect others. The recent outbreak of Ebola virus infection provided an object lesson in the effectiveness of quarantine. Individuals with Ebola virus infection are only infectious after they become symptomatic, and indeed, the likelihood of transmission increases with the duration of symptoms and severity of illness.4 Thus, quarantining symptomatic individuals is a very effective way of interrupting transmission and halting an epidemic. It is notable that (with the occasional exception of healthcare workers) there have been no secondary cases among the imported cases of Ebola virus in the recent epidemic. In contrast, quarantine is a less effective strategy to adopt in cases where individuals are highly infectious before they become symptomatic, such as influenza13 or measles.14 However, a form of quarantine, namely, selective isolation of symptomatic individuals until they are no longer infectious, is often used for these viral illnesses. As an example, policies within healthcare organizations require that healthcare workers who develop influenza do not return to work until symptoms resolve.
Another important public health strategy to deal with infections transmitted from one human to another involves identifying contacts of infected individuals and providing them with either treatment or prophylaxis. Contact tracing (identification and diagnosis of persons who may have come into contact with an infected individual) is an important element of public health prevention strategies for sexually transmitted diseases and tuberculosis (TB). TB is a bacterial disease transmitted through the air, and although rare in developed countries, is most often associated with infection in immigrants.15 The public health approach to prevention of TB starts with identifying infected individuals. In the case of persons with active infection, contacts are identified and screened to determine if they have infection (latent disease) or active disease from TB. Such cases are then offered either treatment (for active disease) or chemoprophylaxis (for latent infection).
Policies exist to allow public health authorities to use an extreme form of control (albeit one that is rarely exercised) to curb the spread of TB. Patients with active TB are quite contagious, but the risk to others is eliminated with effective therapy. In some cases, individuals with infectious TB refuse treatment. In such cases, public health departments have the ability to forcibly incarcerate individuals and mandate treatment. Such draconian laws stem from an earlier era when effective control measures were often not available; however, these laws are still valid in many jurisdictions and have rarely been successfully challenged. In such cases, the courts have accepted that protection of the public outweighs the rights of an individual.
Vaccination as a Prevention Strategy
The public health measure that has had the greatest success in controlling infectious diseases has been the development of vaccination. Indeed, many would regard vaccination as the greatest advance in human medicine ever. Many lethal infections (especially viral infections of childhood) are now merely memories in the developed world, and an effective worldwide vaccination campaign has led to the eradication of smallpox, one of the great killers in human history.16 In the United States, for example, it is estimated that for each birth cohort, childhood immunization prevents 40,000 deaths and as many as 20 million infections.17 Vaccinations involve the administration of an antigen (a living attenuated pathogen, a killed pathogen, or a reactive component of a pathogen), which then stimulates an immune response in the human host. If the host is then exposed to the pathogen, the immune response generated by the vaccine usually prevents infection from being established. In some circumstances, vaccines do not prevent infection but do prevent disease. Vaccinations usually are administered starting in early childhood but can continue throughout life. Enforcement of the use of vaccinations as a public health strategy usually involves demonstrating immune status at various points in an individual’s life. U.S. public health policy now recommends early childhood vaccination against polio, measles, mumps, rubella, pertussis, rotavirus, hemophilus influenza pneumococcus, and varicella.18 Most school districts require evidence of immunity to common childhood infections prior to school admission. Thus, while early childhood vaccination may remain voluntary, the requirement for school admission has been a very important component of public uptake of vaccines.19 Vaccination against hepatitis B and human papilloma virus is also recommended during childhood. Interestingly, these vaccines also prevent cancer because of the role of viral infection in the development of hepatic cancer and cancer of the cervix, respectively. It is recommended that college students and military recruits be vaccinated against meningococcal infection because of the higher risk of exposure associated with these jobs and settings.20
Certain occupations require additional vaccinations as mandatory employment stipulations. Most healthcare workers are required to demonstrate evidence of immunity to hepatitis B (which usually means prior vaccination), and healthcare facilities increasingly are mandating that employees with patient contact undergo annual influenza vaccination. Many jurisdictions require food handlers to present evidence of immunity to hepatitis A (which again usually mandates vaccination) because of evidence that most outbreaks of hepatitis A are a result of fecal contamination from infected hosts. There are also recommendations for other population subgroups. For example, a vaccine against herpes zoster virus is recommended for older adults to boost preexisting immunity and prevent shingles.
There has been tremendous progress in the development of new vaccines over the last 20 years, through both improved vaccines for previously controlled diseases as well as new vaccines for emerging pathogens. This progress has been paralleled, however, by an increasing loss of public confidence for vaccines in general. It is critically important that public health professionals understand and effectively address this public reaction to ensure that vaccination remains a vital part of infectious-disease prevention policy.
The public’s increasing skepticism regarding the effectiveness and use of vaccinations is complex. An individual’s acceptance or rejection of vaccination for herself, or more importantly for her children, may be based on many factors. One of the critical issues with vaccines is that the public health benefit is derived when a large number of healthy individuals are vaccinated. Thus, unlike many other health interventions, vaccination is given to a healthy person and the immediate benefit to that individual may not be apparent. For some infections, there must be widespread immunization of the population to create “herd immunity”—that is, immunity at a population level, and the actual major benefit is not to the vaccinated individual but to unvaccinated members of the community (usually infants too young to be vaccinated themselves). When devastating infections such as polio, measles, and diphtheria were part of “normal” childhood development, parents and families rushed to vaccinate their children to protect them from the fatal or chronically debilitating effects of such infections. In the developed world, however, several generations separate the era when these infections were common from the present day. Today, parents (and even grandparents) have no personal recollection of the potentially catastrophic effects of early childhood infections. This can lead to complacency, which is often coupled with a misplaced confidence that modern medicine can deal with an infection if it does occur. More importantly, the very fact that these vaccines have been so effective means that possible risks of the vaccines (and/or the schedules by which the vaccines are given) have gained greater prominence than they might have gained in an era when the diseases were more common and greatly feared.
A number of interlinking factors have resulted in this false sense of security. Some people are skeptical of the vaccine industry and question the financial motives of large corporations; others are skeptical of science in general and concerned that scientists might minimize risk because of conflicts of interest. A lack of understanding of the scientific process can lead to doubts about science in general. Recommendations are based on emerging data, yet changing vaccination recommendations can be perceived by the public as scientific uncertainty. As scientifically based guidelines and advice changes, confidence in the science can paradoxically decrease. Adverse events may occur by coincidence but are often attributed by individual parents to vaccination because the adverse event coincided with a vaccination. This particular phenomenon has been exacerbated by scientific fraud (as in the case of a putative, but false, link between autism and the measles vaccine22) and by celebrity endorsement.23 Indeed, the entire antivaccination movement has been greatly enhanced by the Internet and social media, which allow for the rapid exchange of information, along with misinformation, and can fuel a self-perpetuating community of doubters.
One additional and disturbing element of decreased vaccination rates among children reflects a form of social elitism, more often seen in affluent and, presumably, more informed communities. In this situation, nonvaccination of children is a conscious decision based on the notion that such parents do not need to vaccinate their children if enough other people are continuing to vaccinate to maintain a community herd immunity.24
Another factor that has added to public concern is the addition of more vaccines to what was already perceived as a robust immunization schedule for children. Some of these are novel vaccines against illnesses for which there was not previously an available preventive strategy. Many others are variations of vaccines that have been available for years, with technical improvements and changes that add to complexity. Furthermore, as new vaccines are introduced, the schedule by which children receive them changes. This increasing complexity of products and scheduling has undoubtedly led to more public questioning of vaccine choices. Furthermore, individual countries have recommended different schedules for childhood vaccination, again raising legitimate questions among the public as to the rationale behind the policy recommendation.25 Public confidence also is challenged when various authorities take different stances on vaccination. This is particularly true in the current Internet and social media era, wherein a government’s decision in one jurisdiction is rapidly disseminated globally. For example, the Japanese government decided in 2011 to temporarily suspend use of the pneumococcal conjugate vaccine and the hemophilus influenzae vaccine while investigating possible adverse events. Although the suspension was short-lived, the event was rapidly disseminated worldwide through social media, leading to widespread disquiet in many communities.
Increased reluctance to vaccinate children has resulted in the re-emergence of dangerous childhood infections. The United States continues to see outbreaks of vaccine-preventable infections that are often linked to initial cases in individuals coming from countries where the diseases are endemic. After initial contact with the infected individual, the outbreak spreads among unvaccinated U.S. residents. About 50–100 cases of measles occur annually in the United States.26 In 2015, a significant multistate outbreak of measles occurred following an index case in a visitor to Disneyland in California.27 (See Box 10.3.) Although most of the cases of measles have been uncomplicated and self-limited, there have been fatalities and complications. Furthermore, ongoing transmission provides substantial risk to the small population of children (e.g., those too young to receive vaccination or with abnormal immune systems) who cannot be immunized and who have a higher risk of dying with infection. In addition to the health consequences of such outbreaks, there are also financial costs to the public health system. For example, two outbreaks of measles in Utah in 2011 involved only 13 cases but were estimated to cost the public health system over $300,000 in additional resources.28 Outbreaks of mumps29 and a steady rise in the cases of pertussis30 (whooping cough) also have been documented in the United States over the last 10 years. It should be emphasized, however, that in both of these diseases, factors other than failure to vaccinate might be playing a role. For example, infections that may be caused by strains not well covered by vaccination, and a lack of complete protection in every recipient, are additional issues that may contribute to these outbreaks.
There is substantial variation among different populations or communities in terms of belief in vaccine efficacy or risk and in terms of trust in government and authority. Success in safeguarding vaccination as a trusted and effective strategy in the prevention of infectious diseases requires an understanding of local factors such as religious beliefs, political will, historical context, and sociodemographics. Understanding these factors can aid in the development of effective strategies to address the issue. For example, the outbreak of measles in California in 2015 has brought much attention to the rights and responsibilities of parents with regard to vaccination. Policies have been seen as a potential solution to address the issue of “rights.” Schools in some areas have considered policies allowing refusal of attendance for unvaccinated children. In 2015, several states introduced legislation to limit or abolish religious exemptions to mandatory vaccination.
Case Study: Policies Related to Health Care-associated Infections
In the United States, it is estimated that 100,000 people die of health care associated infections (HCAIs) in hospitals each year.31 This estimate does not include mortality in nonhospital settings (e.g., outpatient clinics, long-term care facilities, or dialysis centers) that are increasingly a standard part of American health care. These infections are estimated to add at least $30 billion in additional direct medical costs and probably have an even greater economic consequence.32 In spite of these astounding numbers, it is only recently that HCAIs have come to be regarded as a public health problem, and as an issue where policy approaches factor into the solution.33
Traditional public health approaches to control infectious diseases in the community are also applicable in the healthcare setting. Surveillance for sentinel infection rates (e.g., line-associated blood stream infection, postoperative wound infection, and catheter-associated urinary tract infection) has allowed infection control professionals and epidemiologists to identify important preventable risk factors for such infections and to investigate interventions that can decrease rates. Investigation of outbreaks also adds to identification of risk behaviors or practices that can be ameliorated or prevented, quite often via policy. Isolation of patients (a form of quarantine) has decreased transmission of antimicrobial resistant infection. Behavior changes among healthcare professionals, particularly better adherence to hand-washing requirements, are also critical components of infection prevention in the healthcare setting. Increasingly, it has been recognized that a series of policies and practices, bundled together, can significantly decrease, if not eliminate, some of these infections.
From a policy perspective, the most important advance has been the development of federal and state measures to enforce the necessary behavioral responses. All 50 states in the United States have HCAI prevention plans.34 Many states have developed mandatory reporting of certain HCAIs to increase accountability and transparency in hospital settings. From the federal perspective, the Centers for Medicare and Medicaid Services (CMS) have introduced financial incentives to increase adherence to the CDC’s infection control guidance. The CDC has developed a national tracking system, the National Healthcare Safety Network (NHSN), which tracks data on rates of infection with antimicrobial resistant organisms, use of antimicrobials, adherence rates to certain infection control measures, and vaccination rates among healthcare workers.35 The NHSN includes over 12,000 facilities (hospital and other facilities) in all states and has been able to demonstrate encouraging trends toward a decreasing burden of HCAIs in the country. But complacency is not warranted. Certain infections, such as Clostridium difficile infection and multi-drug resistant gram-negative infections have not decreased, and in the case of the latter may be increasing in prevalence.36 In late 2014, legislation was introduced to address the threat of antimicrobial resistant organisms and additional policy changes are being considered. For example, it is likely that the CMS will require all hospitals to implement antibiotic stewardship programs intended to restrict the use of certain drugs so that resistance to them is less likely to emerge and their effectiveness can be maintained for more serious infections and appropriate indications.
Case Study: Policies Relating to Human Immunodeficiency Virus (HIV) Infection
Infection with HIV has been one of the greatest global public health challenges of the last 30 years. Since 1981, there have been over 20 million deaths from HIV infection, and even now, nearly 20 years after the development of effective treatment for HIV, there are 2.5 million new cases of HIV each year across the world and at least 1.5 million people die annually from HIV disease.37 Prevention of HIV infection is without doubt one of the most critical public health challenges of the 21st century.
Transmission of HIV infection is well understood. The major route of infection is sexual and most infection occurs in the setting where neither party is aware of their HIV status. The likelihood of infection occurring during sexual transmission is most strongly correlated with the amount of HIV in the blood of an infected person (viral load). This is highest during acute infection and, therefore, transmission during acute infection is a major driver of epidemic HIV. Transmission also occurs from mother to child during pregnancy (especially in the third trimester), during childbirth, and with breastfeeding. Transmission occurs when individuals have direct inoculation with blood or blood products, as has occurred with blood transfusions and continues to occur with intravenous drug users sharing needles or syringes.
As with other viral infections, the ideal prevention strategy would be an effective vaccine. However, in spite of over 25 years of concerted and well-financed research, a vaccine for HIV has proven elusive. Unlike some other viral infections, live attenuated virus is never likely to be felt a safe proposition for HIV immunization. Current challenges include uncertainty as to what would constitute protective immunity, the genetic diversity of the virus, and great difficulty in finding antigens that can provoke sustained immune responses that might be effective. Therefore, prevention strategies other than an HIV vaccine should be considered.
As indicated previously in this chapter, knowledge of the transmission characteristics can guide effective public health prevention strategies. One of the success stories in HIV prevention has been in the prevention of mother-to-child transmission of the virus. Early clinical trials demonstrated that treating mothers during pregnancy and labor, and treating infants for a short period after birth, could greatly reduce the rate of childhood infection. These studies rapidly led to public health policies of screening all mothers for HIV during pregnancy and offering treatment to infected pregnant women. Initially, all mothers were asked to give consent for HIV testing. Screening policies were further refined to an opt-out approach whereby mothers were assumed to consent unless they formally declined. This policy approach has led to a situation where neonatal and pediatric HIV infection is extraordinarily rare in the developed world, and usually occurs in situations where mothers have had little or no prenatal care. Not surprisingly, the situation is different in the developing world, where availability of effective antiretroviral therapy is much more variable and where antenatal care is less organized. One important policy difference between developed and developing countries concerns breastfeeding. In the Western world, it is recommended that HIV-infected women not breastfeed. However, in the developing world, formula feeding is associated with higher mortality and not breastfeeding may stigmatize the HIV-infected mother. Consequently, prevention policies in the developing world have had to be refined to reflect this reality, and where it is available, current guidelines recommend that the mother continue to receive antiretroviral therapy throughout the period of breastfeeding. This approach is based on evidence that such a policy has the best outcomes for both mother and child.38,39
Prevention of HIV infection by transfusion was rapidly achieved after the development of diagnostic tests for HIV and screening of donors and blood products. Because there remained a small window whereby an infected donor could transmit HIV without testing positive, screening of donors was accompanied by a policy of a lifetime ban on blood donation by individuals, particularly homosexual men, who engaged in high-risk sexual practices. (See Chapter 13 case study for more information on transfusion policy.) As testing technology improved and knowledge of transmission risk increased, this approach made less scientific sense. Nonetheless, it was not until late 2014 that the FDA changed its policy to one that banned individuals who had engaged in high-risk sexual practices during the previous 12 months. Relevant scientific groups, such as the Infectious Diseases Society of America, continue to advocate for a more scientifically based policy that would reduce the window to high-risk behavior in the previous 6 months.
Both behavioral and biomedical approaches have their place in preventing sexual transmission of HIV. Condom use has been known to be effective in reducing HIV risk for many years. However, advocacy of condom use as public policy and education approaches to increase both use and acceptability of condoms have often been hampered by political considerations that ignored scientific evidence. For example, between 2001 and 2008, the CDC was unable to fully advocate for condom use as a strategy in HIV prevention. Instead, public policy focused on abstinence as a strategy, in spite of minimal evidence that such an approach was effective. This is an area where public policy (driven by political and/or religious considerations rather than science) can actually have detrimental effects. Discrimination against male homosexuals is likely to keep such activity hidden, and an abstinence-based approach to prevention actually increases the risk of heterosexual transmission of HIV, as gay men conceal their sexuality.
One of the most critical scientific advances in prevention of HIV infection has been the demonstration that treatment of infected individuals can significantly decrease (and possibly completely eliminate) their risk of infecting uninfected sexual partners.40 There are lower transmission rates in the community when there is a higher proportion of treated HIV-positive individuals in that community. This has given rise to the concept of community viral load. For example, if more HIV-infected people in a community are being treated, there will be less HIV available to infect new patients. Given that most current infections occur via individuals who do not know they are HIV positive, the public policy approach that is now being tested around the world is known as “test and treat.” This would imply developing strategies to increase HIV testing and then increase access to treatment for infected persons. The current CDC recommendations for HIV testing suggest that all patients in healthcare settings should be tested for HIV.
Parallel to the clinical studies that show that treating HIV-infected persons decreases their infectivity, are studies that indicate that giving uninfected high-risk individuals (especially men who have sex with men) antiretroviral drugs can protect them from acquiring HIV infection in spite of continued high-risk behavior.41 This approach is known as pre-exposure prophylaxis or PrEP and is being increasingly used. Opponents to this strategy believe that it will increase the possibility of generating treatment-resistant HIV strains and that it also will increase high-risk behavior, because recipients of PrEP may minimize other protective strategies, such as condom use. Nevertheless, in 2014, the U.S. Public Health Service issued guidelines suggesting that PrEP be considered as an option for individuals at substantial risk for HIV acquisition.
It is important to emphasize that in spite of all the program and policy strategies being implemented, HIV infection remains an important public health challenge. In the United States, the CDC estimates that 50,000 new cases of HIV are acquired each year and that this number has not changed in over 10 years.42 So clearly, better public health approaches, especially ones targeting the communities at greatest risk are needed.
Prevention of infectious diseases has been one of the great public health success stories of the last 150 years. Policies based on sound scientific principles, including understanding of pathogenesis and transmission of infection have been developed and implemented. Most jurisdictions have a public health infrastructure that monitors important infections and has policies to control and/or to prevent many of the important risks to the population. Vaccination policies have led to the virtual elimination of many important infections (especially those of early childhood) in the developed world. However, the risk of infection has not been eliminated. There has been a decrease in funding for public health over the last 30 years, with consequent inadequate responses to emerging or new infections. Trends in globalization and travel have increased the risk of many infections, including vector-borne, food-borne, and zoonotic infections. Antimicrobial resistance and hospital-associated infections are now global problems that will require a multinational and multidisciplinary response.
The policy implications for prevention of infectious diseases are many. Currently, public health professionals at state and local levels have many powers to prevent infectious diseases, as the balance between individual rights and community health needs has played out historically. For certain infections, public health authorities have the right to mandate testing of individuals or communities for communicable illnesses. They can enforce mandatory quarantine or isolation. They can mandate treatment and provide legal sanction against those who refuse therapy. In extreme cases, they can even force individuals to be treated for infectious diseases without their consent.
Development of scientific knowledge may offer novel possibilities for prevention and control with subsequent new or evolved policy implications. However, as we become more precise in determining risk from an infected individual to others in the community, the tension between the rights of individuals and the rights of the general public are likely to become heightened, leading to even more debate about policies appropriate for adoption.
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