Infectious Disease Prevention

Infectious Disease :

Much of the decline in the incidence and fatality rates of infectious diseases is attributable to public health measures—especially immunization, improved sanitation, and better nutrition.
Immunization remains the best means of preventing many infectious diseases. In the United States, childhood immunization has resulted in near elimination of measles, mumps, rubella, poliomyelitis, diphtheria, pertussis, and tetanus. Haemophilus influenzae type b invasive disease has been reduced by more than 9500 since the introduction of the first conjugate vaccines.
However, substantial vaccine-preventable morbidity and mortality continue to occur among adults from vac-cine-preventable diseases, such as hepatitis A, hepatitis B, influenza, and pneumococcal infections. For example, in adults in the United States, there are an estimated 50,000– 70,000 deaths annually from influenza, hepatitis B, and nVasiVe pneumococcal disease. Influenza vaccination is recommended for adults age 50 and older, and it has been documented that annual influenza immunization with Inactivated vaccine (administered intramuscularly) pre¬vents cardiovascular morbidity and all-cause mortality in persons with coronary and other atherosclerotic vascular disease. Rates of influenza vaccination have increased. Self- reported rates of influenza vaccine coverage in adults older than 65 years increased from 300o in 1989 to 70% in 2004. However, vaccination rates were higher for non-Hispanic whites compared with other ethnic minority groups.
The American College of Physicians recommends that clinicians should review each adult's immunization status at age 50; assess risk factors that would indicate a need for pneumococcal vaccination and annual influenza immuni-zations; reimmunize at age 65 those who received an immunization against pneumococcus more than 6 years before; ensure that all adults have completed a primary diphtheria-tetanus immunization series, and administer a single booster at age 50; and assess the postvaccination serologic response to hepatitis B vaccination in all recipi¬ents who have ongoing risks of exposure to blood or body fluids (eg, sharp in)uries, blood splashes).
Strategies have also been proposed to improve influenza, pneumococcal polysaccharide, and hepatitis B vaccination. Strategies to enhance vaccinations in general include increasing community demand for vaccinations; enhancing access to vaccination services; and provider- or system based interventions, such as reminder systems. Increasing reports of pertussis among US adolescents, adults, and their infant contacts have stimulated vaccine development for older age groups. A safe and effective tetanus-diphthena 5- component acellular pertussis vaccine (Tdap) is available for use in adolescents and in adUltS younger than age 65. The Advisory Committee on Immunization Practices (AC.11') I e, int mends routine use 01 a single dose of Tdap for adults aged 19-64 years to replace the next booster dose of tetanus and diphtheria tmoids vaccine (Td). Further research is needed to elucidate the role of vaccination in persons older than 65 years and to determine whether future booster doses of Tdap are needed.
A new recombinant protein hepatitis E vaccine has been developed that has proven safe and efficacious in preventing hepatitis E among high risk populations (such as those in Nepal). Both hepatitis A vaccine and immune globulin provide protection against hepatitis A; however, administration of immune globulin may provide a modest benefit over vaccination in some settings.
Recommended immunization schedules for children and adolescents and adults are set forth in Tables 30-12 and 30-13. Thimerosal-free hepatitis B vaccination is available for newborns and infants, and despite the dis¬proved relationship between vaccines and autism, thime¬rosal-free vaccines are available for pregnant women.
Human papillomavirus (HPV) virus-like particle (VLP) vaccines have demonstrated effectiveness in preventing per¬sistent HPV infections, and thus may impact the rate of cervical intraepithelial neoplasia (CIN) 11-11I. The Ameri¬can Cancer Society and the American Academy of Pediat¬rics (AAP) recommends routine HPV vaccination for girls aged 11-12 years. The AAP also recommends that all unvaccinated girls and women ages 13-26 years receive the HPV vaccine. Trials demonstrate efficacy of bivalent HPV (16/18) or quadrivalent HPV (6/11/16/18)L1 virus-like par-ticle vaccines in preventing new HPV infection and cervical lesions but not in women with preexisting infection. It is estimated that routine use of HPV vaccination of females at 11 to 12 years of age and catch-up vaccination of females at age 13-16 (with vaccination of girls age 9 and 10 at the discretion of the physician) could prevent 95% to 100% of CIN and adenocarcinoma in situ, 99% of genital warts and approximately 70% of cervical cancer cases worldwide; thus, the role of HPV testing will need redefinition. Despite the effectiveness of the vaccine, rates of immunization are low. Interventions addressing personal beliefs and system barriers to vaccinations may help address the slow adoption of this vaccine.
Persons traveling to countries where infections are endemic should take precautions described in Chapter 30. Immunization registries—confidential, population-based, computerized information systems that collect vaccination data about all residents of a geographic area—can be used to increase and sustain high vaccination coverage.

Skin testing for tuberculosis and treating selected patients reduce the risk of reactivation tuberculosis . Two blood tests, which are not confounded by prior BCG (bacille Calmette-Guerin) vaccination, have been developed to detect tuberculosis infection by measur¬ing in vitro T-cell interferon-gamma release in response to two antigens (the enzyme-linked immunospot [ELISPOT], [T-SPOT.TB] and the other, a quatitative ELISA [Quantiferon- TBGlod] test ) . These T-Cell-based assays have an excellent specificity that is higher than tuberculin skin testing in BCG-vaccinated populations. The rate of tuberculosis in thc United States has been declining since 1992, although this decline has slowed in recent years. In 2007 the tuberculosis rate was the lowest recorded since national reporting began in 1953. The Advisory Council for rhe Elimination of Tuberculosis has called for a renewed corn. rnitment to eliminating tuberculosis in the United States, and the Institute of Medicine has published a detailed plan for achieving that goal. Patients with HIV infection are at an especially high risk for tuberculosis, and tuberculosis preventive therapy in the era of HIV will require further work to overcome implementation barriers and to identify optimal duration of preventive therapy and treatment approach for individuals receiving highly active antiretro¬viral therapy (HAART).
Treatment of tuberculosis poses a risk of hepatotoxicity and thus requires close monitoring of liver transaminases. Alanine aminotransferase (ALT) monitoring during the treatment of latent tuberculosis infection is recommended for certain individuals (preexisting liver disease, pregnancy, chronic alcohol consumption). ALT should be monitored in HIV-infected patients during treatment of tuberculosis disease and should be considered in patients over the age of 35. Symptomatic patients with an ALT elevation three times the upper limit of normal (ULN) or asymptomatic patients with an elevation five times the ULN should be treated with a modified or alternative regimen.
HIV infection is now the major infectious disease prob-lem in the world, and it affects 850,000-950,000 persons in the United States. Since sexual contact is a common mode of transmission, primary prevention relies on eliminating unsafe sexual behavior by promoting abstinence, later onset of first sexual activity, decreased number of partners, and use of latex condoms. Appropriately used, condoms can reduce the rate of HIV transmission by nearly 700/0. In one study, couples with one infected partner who used condoms incon¬sistently had a considerable risk of infection: the rate of seroconversion was estimated to be IPA, after 24 months. No seroconversions were noted with consistent condom use Unfortunately, as many as one-third of HIV-positive per¬sons continue unprotected sexual practices after learning that they are HIV-infected. Tailored group educational intervention focused on practicing "safer sex" can red.' their transmission-risk behaviors with partners who are not HIV-positive. Other approaches to prevent HIV infection include treatment of sexually transmitted diseases, develop¬ment of vaginal microbicides, and vaccine developriT. Increasingly, cases of HIV infection are transmitted by 111/e0" tion drug use. HIV prevention activities should include provision of sterile injection equipment for these individuals.

With regard to secondary prevention, many HIV- infected persons in the United States receive the diagnosis advanced stages of immunosuppression, and almost all will progress to AIDS if untreated. On the other hand. HAAR' substantially reduces the risk of clinical progression or death in patients with advanced immtmosuppression. SreenthrT tests for HIV are extremely (> 99%)  Accurate.While the benifits of HIV screening appear to outweigh its harms,current screening is generally based on individual pattient risk factors. Such screening can identify persons at risk  for AIDS but misses a substantial proportion of those infected.

Nonetheless, the yield from screening higher prevalence populations is substantially greater than that from screening the general population, and more widespread screening of the population remains controversial.
In immunocompromised patients, live vaccines are con¬traindicated but many killed or component vaccines are safe and recommended. Asymptomatic HIV infectedpatients have not shown adverse consequences when given live MMR and influenza vaccinations as well as tetanus, hepatitis B, H influenzae type b, and pneumococcal vaccinations—all should be given. However, if poliomyelitis immunization is required, the inactivated poliomyelitis vaccine is indicated. In symptomatic HIV-infected patients, live virus vaccines such as MMR should generally be avoided, but annual influenza vaccination is safe.
Whenever possible, immunizations should be com-pleted before procedures that require or induce immuno¬suppression (organ transplantation or chemotherapy), or that reduce immunogenic responses (splenectomy). How¬ever, if this is not possible, the patient may mount only a partial immune response, yet even this partial response can be beneficial. Patients who undergo allogeneic bone mar¬row transplantation lose preexisting immunities and should be revaccinated. In many situations, family mem¬bers should also be vaccinated to protect the immunocom¬promised patient, although oral live polio vaccine should be avoided because of the risk of infecting the patient.
New cases of poliomyelitis have been reported in the United States, Haiti, and the Dominican Republic recently, slowing its eradication in the Western Hemisphere. Worldwide eradication of poliovirus, including endemic areas such as India, remains challenging.
The current epidemic of highly pathogenic H5N1 avian influenza within duck and poultry populations in Southeast Asia raises serious concerns that genetic reassortment will result in a human influenza pandemic. In 2003 through 2005, there were 138 confirmed cases of human infection with H5N1 avian influenza in Vietnam, Thailand, Indonesia, China, and Cambodia, with a mortality rate of > 50./o. To Prevent and prepare for an increase in human cases, public health officials are working to improve detection methods and to stockpile effective antivirals, such as oseltamivir. The development of an H5N1 vaccine is underway. Two trials have demonstrated development of neutralizing antibodies using a vaccine with varying doses of hemagglutinin antigen.
Herpes zoster, caused by reactivation from previous varicella zoster virus (VZV) infection, affects many older adults and people with immune system dysfunction. Whites are at higher risk than other ethnic groups and the incidence in adults age 65 and older may be higher than previously described. It can cause postherpetic neuralgia, a potentially debilitating chronic pain syndrome. A varicella vaccine is available for the prevention of herpes zoster. Several clinical trials have shown that this vaccine (Zostavax) is safe, elevates VZV-specific cell-mediated immunity, and significantly reduces the incidence of herpes zoster and postherpetic neuralgia in persons older than 60 years. In one randomized, double-blind, placebo-controlled trial among more than 38,000 older adults, the vaccine reduced the incidence of N.herpetic neuralgia by 66% and the incidence of herpes zoster by 51%. The vaccine is administered as a one-time subcutaneous dose (0.65 mL) and is approved for adults 60 years of age and older. However, durability of vaccine response and whether any booster vaccination is needed are still uncertain. The cost effectiveness of the vaccine varies substantially, and the patient's age should be considered in vaccine recommendations. One study reported a cost-effec¬tiveness exceeding $100,000 per quality-adjusted life year saved.
In 2008, the United States Preventive Services Task Force (USPSTF) reviewed evidence to reaffirm its recom-mendation on screening for asymptomatic bacteriuria in adults. New evidence was reviewed, which continues to support routine screening in pregnant women but not in other groups of adults.