Emergence and Control of Viral Respiratory Diseases (2005)

and Control of Viral Respiratory a symposium

Les Pensieres, Veyrier du Lac, France 

November 30–December 3, 2004

Pandemic influenza is imminent and severe acute respiratory syndrome (SARS) may reappear. In addition, well-characterized diseases may reemerge through accidental or deliberate release of biologic agents. New diseases are likely to emerge at an accelerated frequency because precipitating factors already exist. Increased surveillance and preparedness are keys for prevention and control. These were the predominant conclusions of delegates from Europe, America, and Asia who met at the symposium on Emergence and Control of Viral Respiratory Diseases, organized by the Merieux Foundation with the support of Sanofi Pasteur, November 30–December 3, 2004, at Les Pensieres, Veyrier du Lac, near Annecy, France (in the French Alps). Participants assessed the role of ecologic, viral, and host factors, as well as strategies for prevention and control through surveillance, vaccination, and treatment.

Many factors contribute to the ability of viruses to cross and their dissemination in humans. Fifty percent of known human pathogens and nearly 75% of all emerging infectious diseases are zoonotic in origin. Many of these pathogens have spilled over from natural wildlife reservoirs into human populations, either directly or through contact with domestic or peridomestic animals. Viruses evolve quickly, and many disease-causing agents already exist in nature. Pathogens jump often, in spite of species barriers, which vary from pathogen to pathogen. For viruses, the barrier may include receptor specificity, the need for coreceptors, different favorable temperature conditions, host-specific transcription factors, or innate immunity. However, modern conditions provide ever greater opportunities for viruses to cross species. An increase in world population is driving a need to develop new territories and to find new sources of food and water. More are being raised or hunted for food, thus contributing to a juxtaposition of animal and human populations (Steven S. Morse, Columbia University, New York, NY, USA, and Jonathan Epstein, Consortium for Conservation Medicine, Palisades, NY, USA).

Respiratory pathogens can be transmitted through air and water. Fungal spores can be transported globally in clouds of desert dust. Human wastewater is affecting coastal water quality on a global scale. Globally, ≈90% of sewage generated in coastal environments is released untreated, and the wastewater contains high numbers of fecal-oral pathogens, particularly viruses, which can survive for extended periods. The wastewater-associated viruses can cause a variety of illnesses, including gastroenteritis, ocular infections, hepatitis, myocarditis, and respiratory diseases. (Dale Griffin, U.S. Geological Survey, St. Petersburg, FL, USA). In zoonotic infections, although many interspecies transfers are dead ends, sometimes viruses evolve through mutation, recombination, or reassortment and acquire the potential to spread from human to human. RNA viruses, which lack proof mechanisms to ensure fidelity of the genome, accumulate mutations during replication and are the most able to adapt to new hosts. However, RNA viruses have diverse evolutionary histories. The evolutionary trajectories of measles, caused by a morbillivirus that emerged 2,000–5,000 years ago, and AIDS, caused by a retrovirus (HIV-1) that originated in the 20th century, have been quite different. The pandemic form of HIV-1, group M, originated around 1930 and has diversified through rapid mutation and recombination, whereas measles viruses evolve ≈10 times more slowly (Paul Sharp, University of Nottingham, Nottingham, UK).

Human activities, including migration and travel, may disseminate a localized outbreak. During the 1990s, >5,000 airports had regularly scheduled international flights, and ≈2 million persons crossed international borders daily. The World Tourism Organization anticipates 1.6 billion international tourists by 2020 (Mary Wilson, Harvard School of Public Health, Boston, MA, USA).