Conservation medicine is a new field, devoted to the study of the connections between human health, animal health and ecosystem health.

Traditionally, scientists have tended to specialize - that is, to narrow their focus to become experts on a certain plant or animal species. Sub specialties are increasingly common: there are physicians who only see patients with one specific type of kidney disease; plant biologists may study just one species of mushroom. I know a "canine cardiologist" - a veterinarian who exclusively treats dogs with heart problems.

In this world of specialization, it's uncommon for scientists to work with others outside their fields. However, it is becoming increasingly important to view the world with a wide lens in order to see the interconnectedness of life.

As emerging diseases such as West Nile virus, SARS and Ebola have been making headlines, scientists from many fields have started working together to understand how these diseases affect humans and animals, and how environmental factors play a role in the spread of disease.

Conservation medicine - also called conservation health, medical geology or ecological medicine - recognizes many factors affect human and animal health and disease, such as:

• Global climate change

• Loss of biodiversity; extinctions of plant and animal species

• Human population growth

• The growth of human development into previously unpopulated areas

• Poverty and crowded living conditions

• Overuse of antibiotics

• Deforestation, especially of tropical rainforests, and other habitat destruction

• International trade and travel

• Air pollution, especially from the burning of fossil fuels

• Water pollution and the scarcity of clean drinking water.

Although some scientists have always acknowledged the connections between the environment and health, the term "conservation medicine"did not come into use until about 1996. Since then, veterinarians, physicians, wildlife biologists, ecologists and other scientists at Tufts, Harvard and Johns Hopkins universities, the Wildlife Trust (a nonprofit conservation organization) and the U.S. Geological Survey National Wildlife Health Center have joined together to create the Consortium for Conservation Medicine.

A deadly infectious disease called hantavirus illustrates how climate change, wildlife populations and human health intersect, and how important it is for scientists from different fields to work together to understand and halt the spread of new diseases.

Hantavirus pulmonary syndrome emerged in the southwestern United States in 1993; there have been 387 reported cases since then. Humans can be infected with the hantavirus by exposure to the saliva, urine or feces of infected rodents, especially the deer mouse. About 35 percent of humans infected with hantavirus will die of respiratory failure.

Why did hantavirus emerge so suddenly? A six-year drought had killed off many predators - coyotes, foxes, owls and snakes - that usually kept the deer mouse population in check. In the two years of heavy rainfall that followed, the population of deer mice exploded, and contact between the mice and humans increased accordingly.

A large percentage of newly emerging diseases are passed to humans from animals. Some examples:

• West Nile virus is carried by mosquitoes, which infect humans, horses, more than 130 species of birds and possibly other species.

• Avian influenza (bird flu) is a virus carried by birds, including as chickens, ducks and turkeys, which can infect humans who have contact with their saliva, nasal secretions or feces.

• Monkeypox virus is carried by African rodents, who can infect American rodents including rats, mice, rabbits and prairie dogs. It can be transmitted to humans by contact with blood or bodily fluids of an infected animal, by direct contact, or by a bite.

The most important aspect of conservation medicine is the increasing recognition that all species are interconnected. Human health is dependent on the health of all creatures, great and small, plants and animals alike.

Kathryn B. Brown is a family nurse practitioner with a master's degree in nursing from OHSU. Is there a health topic you would like to read about? Send ideas to you can find more local health news and information in the Health section at