Infectious Disease: Most Important of the Modern Plagues

The last few months in Canada have seemed almost biblical in character. We have had plagues, cattle disease, insect infestations, fire, darkness and, if we go back a few years, the Walkerton water disaster could substitute for blood in the Nile. I have put my eldest son on full alert!

For physicians, the most important of these modern "plagues" are those caused by infections. Not unexpectedly, new infectious diseases, like the older more established ones, often have their most devastating effects on older patients. We have known for years that the deaths attributed to influenza outbreaks are most common in older adults. The case fatality ratio for SARS increases quickly with advancing age, and the most serious consequences of last year's West Nile Virus outbreak in southern Ontario also were seen most frequently in older adults.

It is thus very timely that this issue of Geriatrics & Aging focuses on infections in the older adult. During the first wave of SARS in Toronto, a colleague in the U.S. contacted me. He is a specialist in emergency medicine who has developed a successful business providing medical coverage to cruise lines. He was desperately seeking information about SARS to inform the cruise lines about proper infection control procedures. It is perhaps not surprising that infection control is becoming a major issue for cruise lines, since cruises are essentially the confinement of a population the size of a small town to a relatively small area. I found out from my American colleague that Canadians in general, and Torontonians in particular, are high-frequency cruisers. Thus, I think the article "Prevention of Tropical Illness in Older Travellers: The Older Cruiser" is particularly relevant as we head into the first "post-SARS" cruise season.

Everybody agrees that asymptomatic bacteriuria in older adults should not be treated. The more difficult question, however, is how to know whether the patient is truly asymptomatic. One of the few people qualified to address this topic properly is Dr. Lindsay Nicolle, one of North America's leading infectious disease specialists with a long-standing interest in urinary tract infections in older adults. New treatments often come with new risks, and Dr. Richard Long discusses the new biologic therapies and the risk of tuberculosis in older patients. Dr. Shelly McNeil and colleagues focus on long-term care facilities in their review of methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, while Dr. Lona Mody examines the clinical manifestations and treatment options for skin and soft tissue infections. Dr. I.W. Fong discusses one of the most interesting and prevalent "infectious" diseases--atherosclerosis. Although not yet confirmed, evidence for the relationship between infection and atherosclerosis, reviewed here, continues to accumulate.

Finally, I am pleased to announce that three prominent Canadian physicians (and previous contributors to Geriatrics & Aging) have joined our Advisory Board. Dr. Serge Gauthier is an internationally renowned neurologist with a special interest in dementing disorders, Dr. Jagdish Butany is a leading expert in cardiovascular diseases and cardiovascular pathology, and Dr. Rory Fisher is probably the single most important person in the development of Geriatric Medicine as a specialty in Canada. The entire editorial staff at Geriatrics & Aging is pleased to have such distinguished members join our team.

Enjoy this issue.

Survivors of the Age of Tuberculosis, the Elderly are Still Subject to Reactivation of the Disease

Common Presentations, Diagnostic Strategies, and Principles of Treatment

Michael A. Gardam MSc, MD, CM, FRCPC
Medical Director,
Tuberculosis Clinic,
Associate Hospital Epidemiologist,
University Health Network,Toronto.

The elderly are one of four sub populations in Canada, which also include the foreign born, homeless persons, and Native Canadians, that are at high risk for developing active tuberculosis. There are several reasons why tuberculosis is common among the elderly: Firstly, today's elderly have a high possibility of being infected with M. tuberculosis. They are survivors of the earlier part of the twentieth century in which an estimated three-quarters or more of the population were infected with tuberculosis by the time they were 30 years of age. Secondly, the elderly often suffer from other conditions which predispose them to reactivation of tuberculosis, such as diabetes mellitus, chronic renal failure, malnutrition, and diseases requiring prolonged corticosteroid therapy. Finally, residents of nursing homes and long-term care facilities may become infected or reinfected through contact with other residents with active disease.

Symptoms
While the clinical symptoms of tuberculosis may be vague and non-specific in any age group, this is particularly true in elderly persons. Fever, malaise, weakness, and failure to thrive are the most consistent symptoms.

From Sanatorium to Sophisticated Tuberculosis Unit

Kimby N. Barton, MSc
Assistant Editor,
Geriatrics & Aging

I have to admit that I was feeling more nervous than I had expected as I placed the mask over my face. Until this point the reality of my being about to enter a unit with patients who have active tuberculosis (TB), and are capable of infecting me with the disease, had not really sunk in. Suddenly, it seemed vitally important for the mask to form a proper seal around my nose and under my chin to ensure that no bacteria could enter any gap left between the mask and my face. Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis. Infection may result from the inhalation of minute droplets of infected sputum; hence the need for a sealed mask to protect me from accidentally inhaling any bacteria. Having secured the mask, I was ready to enter the inpatient tuberculosis clinic at West Park Hospital.

Tuberculosis is a devastating disease. It is suspected that TB has plagued humankind for more than 2000 years, and in fact, several reports describe Egyptian mummies, almost 4000 years in age, showing signs of tubercular decay in their skeletons! It is estimated that almost one third of the global population is infected and that there are 7 to 8 million new cases per year. In Canada, approximately 2000 new cases of TB occur each year, almost one-quarter of these in Toronto. In almost 90% of these cases the patients are recent immigrants from areas where TB is still a common problem.

Protecting the Elderly Against Influenza: When and How is Vaccination Made Most Effective?

D'Arcy L. Little, MD, CCFP
Director of Medical Education
York Community Services, Toronto, ON

Introduction
Influenza, an acute respiratory illness, causes more adults to seek medical attention than any other respiratory infection. In Canada, influenza is a seasonal disease, causing annual epidemics that affect 10-20 percent of the population and result in approximately 4,000 deaths, 70,000 hospitalizations, and 1.5 million days of lost work.¹ The elderly (people aged 65 years and older), and those with chronic cardiopulmonary disorders, diabetes and other metabolic diseases, have an increased risk of developing influenza complications. Hospitalization rates among elderly patients increase markedly during major influenza epidemics, and 90% of the deaths attributed to influenza and pneumonia are observed in this population.²

Vaccination remains the most reliable means of preventing an influenza infection and the resultant morbidity and mortality. Despite the significance of influenza, efforts to vaccinate the elderly remain suboptimal. A large study conducted in the Netherlands revealed that healthy elderly people avoid influenza vaccination because they fear the side effects, and because they believe that their general health is good and that the benefits of vaccination are, therefore, minimal.

Chasing Away the Flu Bug

An 'Achilles Heel' in Viral Replication Helps Researchers Develop a Universal Cure for Influenza

Nadège Chéry, PhD

When influenza attacks, it may infect anyone, regardless of his or her age. But when influenza kills, it usually takes the lives of individuals, like the elderly, who are less able to fight back.² In Canada, 6000 deaths are attributable to influenza every year³ with the highest rate of mortality occurring among people over 65 years of age.² Thus, when it comes to older individuals, both early diagnosis, and prevention are imperative. Because the influenza virus continuously changes, strategies for the prevention of flu outbreaks, although thoughtfully planned, have had limited success. Recently, however, scientists have found a "weakness" in influenza's ability to escape traditional flu therapies. This discovery has set the stage for the design of new antiviral drugs which, potentially, may constitute a cure for the flu.

What is Influenza?
Influenza is a member of the Orthomyxoviridae family,1 and causes disease by infecting the epithelial cells that compose the lining of the respiratory tract. Influenza produces symptoms similar to other viruses which infect the respiratory tract. Flu outbreaks are common among elderly persons, particularly in nursing homes.⁴ Since the immune systems of elderly people in a nursing home may be compromised,⁵ their ability to fight an influenza infection can be severely undermined.

The Mantoux Test for TB--When to Administer, How to Interpret

Michael A. Gardam MSc, MD, CM, FRCPC
Medical Director, Tuberculosis Clinic
Associate Hospital Epidemiologist
University Health Network

What is a Skin Test and How is it Administered?
Tuberculin skin testing is the most established method of diagnosing tuberculosis infection, that is both active disease and asymptomatic latent infection. Different skin testing techniques have been developed over the past 70 years. The Mantoux test, however, is the standard procedure in North America. The Mantoux test involves the intradermal injection of 0.1 ml of purified protein derivative (PPD--a precipitate prepared from filtered heat-sterilized cultures of Mycobacterium tuberculosis). The only absolute contraindication to administering the test is a history of anaphylaxis induced by any of the components. Those with a history of BCG vaccination may be skin tested.

The test is usually administered in an area that is free of blood vessels, hair or edema, on the flexor surface of the forearm, but it may also be administered on the upper chest or back. The needle should be inserted just under the skin with the bevel facing up until the bevel is fully inserted. A bleb should be raised when the PPD is injected. If this is not accomplished, or the PPD leaks out onto the skin, the test should be readministered in a different site. The test must be read at 48 to 72 hours by a trained healthcare professional.

Why Shingles Occurs Mostly in Seniors

Gradual Immunologic Decline Explains Frequency of Herpes Zoster Among the Elderly

John M Conly, MD,CCFP, FRCPC, FACP
Consultant, Infectious Diseases
Director, Infection Prevention and Control
University Health Network (Toronto General,
Toronto Western and Princess Margaret Hospitals)
Professor of Medicine, University of Toronto

Introduction
Although it is now understood that varicella-zoster virus (VZV) is the etiologic agent for both varicella and herpes zoster, it is of historical interest to note that in the early medical literature, the clinical illnesses of varicella and herpes zoster were considered separate entities. Just six decades ago it was still taught at Harvard University that these viruses were unrelated.¹ In 1943, a pediatrician named Garland suggested that zoster may be due to the reactivation of a latent varicella virus,2 but it was not until 1958 that VZV was definitively recognized as the etiologic agent for both varicella and zoster.^3,4 The VZ virus is a DNA virus and is a member of the Herpesviridae family bearing many distinct similarities to other members of this group of viruses. The virus is spread by direct contact, by droplet and airborne routes from vesicular fluid of skin lesions, or from secretions from the respiratory tract.⁵ Transplacental transmission has also been documented.