This article is the first in a two-part series discussing and illustrating the application of statistical process control (SPC) to processes often examined by hospital epidemiologists. The basic philosophical and theoretical foundations of statistical quality control and their relation to epidemiology are emphasized in order to expand mutual understanding and cross-fertilization between these two disciplines. Part I provides an overview of quality engineering and SPC, illustrates common types of control charts, and provides references for further information or statistical formulae. Part II discusses statistical properties of control charts, issues of chart design and optimal control limit widths, alternate possible SPC approaches to infection control, some common misunderstandings, and more advanced issues. The focus of both articles is mostly non-mathematical, emphasizing important concepts and practical examples rather than academic theory and exhaustive calculations

Recent evidence demonstrating the efficacy of zidovudine, as well as experience with protease inhibitors, led to revision of recommendations for occupational exposures to human immunodeficiency virus-infected blood. At our hospital, this resulted in significant increases in rates of reported exposures and prophylaxis initiation. Among 10 healthcare workers given three-drug, protease-inhibitor-containing regimens, five completed 4 weeks, two completed 4 weeks of two drugs, and three stopped due to intolerance. Three workers missed work due to side effects

Streptococcus pneumoniae is most prominently a major cause of community-acquired infections of the respiratory tract, central nervous system, and bloodstream, but there is an increasing interest in its role in the epidemiology of hospital-acquired infections. Penicillin-resistant pneumococcal strains appeared 3 decades ago and now are present worldwide, often displaying multiple resistance due to antibiotic selective pressure. Horizontal spread can cause either sporadic cases or hospital outbreaks, primarily in younger children and elderly patients. Pneumococcal transmission from one patient to another can be documented by polymerase chain reaction or pulsed-field gel electrophoresis typing. Nosocomial acquisition of infection, along with pediatric age, previous hospitalization, and previous β-lactam therapy, are the main risk factors significantly associated with penicillin-resistant pneumococcal infections. Nosocomial acquisition also is associated with higher mortality from pneumo-coccal disease. The importance of penicillin resistance as a risk factor significantly associated with higher mortality from pneumococcal infection is found in some studies, but not in others. Mortality from pneumococcal pneumonia is approximately the same for human immunodeficiency virus (HIV)-infected patients without acquired immunodeficiency syndrome (AIDS) as for HIV-negative subjects, but it is significantly higher in AIDS patients. Penicillin-resistant strains are involved in the vast majority of hospital outbreaks, whether presenting as clinically manifest infection or a simple colonization. Pneumococcal vaccination is recommended universally in order to lower the incidence of invasive infection, although a number of problems can limit its effectiveness.

Waning pertussis immunity and spread of pertussis by asymptomatic adults contributes to increased pertussis exposures of vulnerable children. The Santa Clara Valley Medical Center had 49 pertussis exposures between July 1, 1989, and June 30, 1997, which originated in pediatric units or clinics and had an impact on the Employee Health Service (EHS) and Emergency Department (ED). We have developed a standardized protocol for management of employees and patients exposed to pertussis. The protocol includes a checklist for infection control staff; memoranda to exposed units conveying exposure information, instructions for employees to report to EHS or ED, and disease symptom information; written guidelines for physician management of patient exposures (prophylaxis and isolation) and EHS or ED management of employee exposures; and prophylaxis recommendations. We allow exposed employees to work while wearing a mask (worn until 5 days of prophylaxis are completed or for the entire potential contagious period if prophylaxis was refused). Employees who develop pertussis are restricted from work. Our protocol and standardized forms provide consistent management of pertussis exposures in both patients and employees.

OBJECTIVE: In June 1996, a resolution was introduced to the House of Delegates of the American Medical Association (AMA) asking the AMA to advocate that healthcare workers be given the informed option of receiving the varicella vaccine. The AMA Council on Scientific Affairs studied this issue and presented this report to the House of Delegates in June 1997.

METHODS:Information for the report was derived from published literature and from personal communications with medical and public health experts and the vaccine manufacturer.

FINDINGS: Nosocomial outbreaks of varicella-zoster virus (VZV) can result in serious morbidity and mortality. Sero-logical testing of healthcare workers and immunization of nonimmune individuals is recommended by infection control and infectious disease experts to prevent nosocomial transmission of VZV. While current data indicate that the vaccine is safe and poses minimal risks to both adults and children, ongoing research should address various concerns about the long-term safety, efficacy, and epidemiological impact of more widespread use of the vaccine.

CONCLUSION:Unless contraindicated, all susceptible healthcare workers should receive the varicella vaccine. Whereas individuals with a definite history of VZV infection can be considered immune, those with a negative or uncertain history should undergo serological testing and, if seronegative, should be immunized

We analyzed 333 isolates of Streptococcus pneumoniae from adult inpatients over a continuous 30-month period. Twenty-five percent of isolates were resistant to penicillin, and 18% of tested strains were not susceptible to ceftriaxone. For 29 (15%) of 199 evaluable patients, S pneumoniae was isolated from a culture first obtained >48 hours after admission, and chart review satisfied our case definition for nosocomial infection. S pneumoniae isolates were penicillin-resistant in 14 of 29 nosocomial and 34 of 170 community-acquired cases (odds ratio, 3.73; 95% confidence interval, 1.53-9.15; P =.01)

A detailed description is presented of the hemodialysis treatment for 6 weeks of a patient strongly positive for hepatitis B virus ([HBV], hepatitis B surface antigen, hepatitis B e antigen, HBV DNA), which was performed without any special precautions. All 59 patients potentially exposed to the HBV-positive patient, of whom 29 appeared fully unprotected by antibody, were followed for at least 9 months but remained negative. This illustrates the feasibility of following Universal Precautions instead of using exceptional procedures for one single agent

The following article, “Microbiological Hazards Related to Xenotransplantation of Porcine Organs in Man” inaugurates this section of the Journal, which will focus on the interface between the world of emerging infectious diseases and the delivery of healthcare. Emerging infectious diseases, that is, diseases of infectious origin whose incidence in humans has increased within the past 2 decades or threatens to increase in the near future, are of great importance to hospital epidemiologists and infection control practitioners. Many of the diseases in this category, eg, Clostridium difficile colitis, infections caused by methicillin-resistant Staphylococcus aureus or van-comycin-resistant enterococci, and legionellosis, are well-recognized causes of nosocomial infections. Others, such as hepatitis C virus, human immunodeficiency virus, and Ebola virus, are potential threats to healthcare workers in certain occupational settings. Still others, group B streptococcal infections in neonates, for example, may be prevented by implementation of strategies that infection control programs can promote.

Control charts are essential tools in the statistical process control armamentarium. Although designed for ease of use in highly structured production settings, they are in fact quite complex in nature; their proper use depends on numerous conditions that may not be clear to newer users. This article briefly contrasts the use of control charts in production and healthcare settings and highlights common sources of problems among novice users. These include misunderstandings of the type of data being charted, non-independence of samples, the influence of natural cycles, ignoring known special influences, overlooking clear signals that a process is out of control, and calculating control limits before adequate data are available.