Are most chronic illnesses really infectious diseases?
By Deborah Gesensway
PHILADELPHIA—Imagine vaccinating patients against heart attacks or type 1 diabetes, or prescribing an antibiotic to get rid of kidney stones. Due to advances in molecular biology and imaging technology, these medical advances may not be as far-fetched as they sound.
Researchers are linking chronic illnesses no one ever suspected of being infectious—such as ulcers—to microorganisms, raising new questions about diagnosis and treatment. These developments prompted Bennett Lorber, FACP, to pose an intriguing question to attendees at an Annual Session course: "Are all diseases infectious?"
"The answer, of course, is 'No,' " said Dr. Lorber, chief of the infectious diseases section at Temple University School of Medicine. "Scurvy is not an infection ... but all the important diseases are!"
He may have offered that conclusion partly in jest, but medical science in the last decade has made such leaps in understanding microorganisms that his words may prove prophetic. Researchers have proven that infectious agents play a role in many chronic illnesses from cancer to kidney disease.
Experts now have a much greater understanding of how microorganisms may cause, trigger or increase the risk of getting a disease. Research into how infectious agents "stick" to a specific receptor—the step in which exposure to an infectious agent leads to disease—will help scientists understand how to combat these infections.
"I really believe that in our lifetime, we will treat many of these infections with 'antistick' agents rather than antimicrobial agents," he said. "We will also develop vaccines to block sticking sites and prevent disease."
During his Annual Session presentation, Dr. Lorber summarized the current thinking about several diseases that until recently no one suspected of being infectious.
Bell's palsy. Most Bell's palsy cases are caused by the herpes simplex virus. Dr. Lorber described one study in which Bell's palsy patients treated with steroids and acyclovir recovered faster and more completely than those treated with steroids alone.
Cancer. From human papillomavirus causing cervical cancer to human herpes virus-8 causing Kaposi's sarcoma in HIV/AIDS patients, numerous infections have been linked to different forms of cancer, Dr. Lorber explained. "With new microbiology techniques," he said, "I'm sure we will learn about many more."
Coronary artery disease. Numerous serological studies have linked heart attack risk to the presence of the common respiratory pathogen Chlamydia pneumoniae. "More than two dozen studies have shown that C. pneumoniae is frequently found in diseased coronary arteries," he said, "but not in normal coronary arteries."
Several ongoing studies are looking at using antibiotics for primary and secondary prevention of heart attacks, he added, but the findings have been disappointing.
Diabetes. There is evidence that enteroviruses play a role in the onset of type 1 diabetes. Pancreas biopsies from patients with newly diagnosed insulin-dependent diabetes contain these viruses, Dr. Lorber pointed out, and studies in mice have proven this infectious link.
Dr. Lorber also described a "perplexing" national study in the Oct. 17, 2000, Annals of Internal Medicine that described an association between hepatitis C and type 2 diabetes. "How they are associated is unclear," he said, "but it's intriguing."
Guillain-Barre syndrome. Scientists are learning that in most cases, people get Guillain-Barre syndrome after a gastrointestinal infection. These infections usually involve the Campylobacter jejeuni bacterium, the most common cause of bacterial diarrheal illness in the United States.
Mental illness. Antibody measures and molecular probes now link bornaviruses—a new class of virus scientists are only beginning to understand—to schizophrenia, bipolar disorder and major depression. "We will hear a lot more about these," Dr. Lorber predicted.
In addition, he said, researchers have begun to describe an infection in children who develop obsessive-compulsive behavior or Tourette's syndrome after having a group A streptococcal infection. They have labeled these disorders pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, or PANDAS.
Peptic ulcer disease. Although researchers realized nearly 25 years ago that most ulcers are caused by Helicobacter pylori, Dr. Lorber said the CDC recently found that nearly half of all primary care physicians and 30% of gastroenterologists still treat ulcers without looking for or treating H. pylori. "We still have a long way to go," he said.
Spongiform encephalopathies. Stanley B. Prusiner, MD, won the Nobel Prize for Medicine in 1997 for discovering tiny infectious agents called prions (proteinaceous infectious particles). These agents are responsible for some degenerative neurological diseases, such as Creutzfeldt-Jacob disease, once thought to be purely genetic. "Now we know they are transmissible," Dr. Lorber said.
Deborah Gesensway is a freelance writer in Glenside, Pa.
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