Cultural effects on the development of chronic diseases need to be addressed by all who share in the responsibility to diminish the impact of those diseases on our society.
The possibility that infectious agents may cause chronic medical illnesses has been hinted at for centuries. The technical advances of past decades have enhanced our capabilities in microbial detection and enabled us to show that infectious pathogens are at least part of the reason for the progression of several chronic diseases and cancers.
In 2005, two Australian scientists were awarded the Nobel Prize in physiology or medicine in part for their discovery that a common pathogen, Heliobacter pyloris, can cause gastric ulcers and gastric adenocarcinoma. However, they also received the prize for fundamentally changing our perceptions of the link between transmissible agents and certain disorders and conditions that traditionally were perceived as noninfectious, noncommunicable maladies.
There are several pathological and physiological factors that determine the development of chronic ailments.1 The kind of pathogen involved, the time of infection, the duration of the infectious assault and the affected tissue or organ system all will influence the nature of a chronic disease and its outcome. Furthermore, it has been speculated that the resulting disease entity is influenced by a particular mode of the pathogenic insult.
For example, the development of a chronic illness may be due to direct damage by the acute infection or direct damage through a persistent infection. It may result from genomic integration or harmful effects of the body’s immune response. The commonality among all these interactions is the initial infection by a pathogen that could be of bacterial, fungal or viral origin, or even a prion.
The realization that infectious agents may be associated with chronic diseases has spawned the development of specific preventive measures. One of the most important—and most controversial—is immunization against cancers. The first effective vaccine against cancer was aimed at the hepatitis B virus, which together with the hepatitis C virus is linked to primary hepatocellular carcinoma.
More recently, the U.S. Food and Drug Administration approved a vaccine against human papilloma virus, a pathogen associated with cervical cancer. No vaccines are available for other cancers connected to infectious pathogens, such as bladder cancer, Burkitt’s lymphoma, acute T-cell leukemia and lymphoma, or Kaposi’s sarcoma. Still, the path to prevention and treatment has been sighted.
It is not known whether all infectious agents have the potential to induce chronic conditions when circumstances allow. In developing countries, infectious pathogens are more commonly associated with acute conditions and are main contributors to high rates of morbidity and mortality. The scenario is different in developed countries, where most infectious diseases can be treated more effectively. In developed nations, the highest rates of morbidity and mortality are associated with chronic conditions—cardiovascular disease, cancer and diabetes mellitus.
While these three conditions have been linked to infectious agents, they also share common risk or "lifestyle" factors such as tobacco and alcohol use and obesity. Associations among different risk factors in different environments suggest that socioeconomic and cultural aspects may influence the development of chronic conditions.
The idea that cultural traits could be "transmitted" among people was first introduced by evolutionary biologist Richard Dawkins 30 years ago.2 He looked at different behavioral traits that permeate our society and coined the term "meme" to mean a measurable unit of cultural transmission. It might be useful to apply this concept as a way to further our understanding of how risk behavior affects the development of chronic diseases.
It is not known whether all infectious agents have the potential to induce chronic conditions when circumstances allow.
Our understanding of the role of traditional and emerging risk factors in the etiology of chronic diseases is evolving rapidly. In the oral health care arena, this is most evident in the often-discussed associations between oral infectious agents and coronary heart disease, diabetes, adverse pregnancy outcomes and other medical conditions.
Forty years ago the prevailing thought was that infectious diseases had been conquered. Today, we need to revise this notion and acknowledge that infectious agents are among us and are a major cause of numerous chronic diseases and cancers—and may even affect the health of our offspring.
Researchers who bring us this scientific information also need to recognize that infectious agents may be only a part of a more complex etiology. Management of infectious chronic diseases is the basis for oral health care prevention and treatment. However, this is not the case in medicine, in which infectious diseases are mostly approached as episodic, acute or self-limiting events.
Maybe the oral health disease management approach, which has proved highly successful, is a workable model that should be used for chronic medical diseases. Nevertheless, cultural effects on the development of chronic diseases—Richard Dawkins’ memes—need to be acknowledged. They need to be addressed, not only by providers, but also by policy-makers and professional organizations, all of whom share in the responsibility to diminish the impact of chronic diseases on our society.
