MDNews - Minnesota

unexpected consequences of ecosys- tem degradation. Kris Murray, PhD, senior research scientist at EcoHealth Alliance — an international scientific organization focused on biodiversity and conser vation — notes that the magnitude of the impact of human- i n d u c e d e n v i r on m e nt a l c h a n g e s is unpredictable. "We've seen a bunch of new diseases in humans over the last few centu- ries," Murray explains. "Most of these diseases come from animals, and spe- cifically from wildlife. Some of these have changed the course of human history, like plague and influenza. With land-use change and environmental alteration, we are creating new avenues and opportunities for novel pathogens to get into the human population. We have to be prepared for the fact that some of these could again shape our futures." On June 5, 1981, the emergence of what would become the defining health crisis of subsequent decades was described in the CDC's Morbidity and Mortality Weekly Report. At the end of the year, 121 people had died from complications due to severe immune deficiency. The following year, the CDC defined Acquired Immune Deficiency Syndrome (AIDS) for the first time, and 618 deaths were reported. By the end of the decade, more than 120,000 people had died from AIDS, and 15 years later, it was the leading cause of death among American men between the ages of 25 and 44. Upwards of 35 mil- lion people currently live with human immunodeficiency virus (HIV) or AIDS. Researchers believe HIV — a blood- borne pathogen — was first transmitted to humans from infected chimpanzees in western Africa. "The prevailing view of its emergence is that it jumped to people after hunters were exposed while butchering or eating infected animals," Murray explains. "But if humans have been involved in these practices for millennia, then why did HIV only emerge so recently? Some have arg ued that the answer to this question lies in land-use and environmental changes that began to occur in some areas of Africa during the 20th century." He adds that as humans constructed roads traversing previously remote areas, contact with animals increased, "almost certainly [facilitating] the initial spread of HIV." Murray currently researches Nipah virus (NiV), an emerging zoonotic dis- ease initially identified in 1998, after an outbreak in Malaysia. To date, NiV has infected several hundred people and carries a mortality rate of approximately 75 percent, according to Murray. Land-use changes contributed to the initial Malaysian outbreak, as humans encroached on the habitat of fruit bats. Unlike the HIV emergence hypothesis, NiV didn't jump directly to humans from the bats. In this case, bats were brought into close contact with pigs raised on mixed-crop farms. Researchers traced the disease's path from bats to pigs to humans. S u b s e q u e nt N i V o u t b r e a k s i n Bangladesh and India followed different transmission patterns. In 2004, some Bangladeshis became infected after ingesting date palm sap contaminated by infected fruit bats. In India, there are documented cases of human-to-human transmission in hospitals, according to the World Health Organization (WHO). Changing Vectors Vec tor-bor ne d isea ses — wh ich i n c l u d e m a l a r i a , d e n g u e f e v e r, lei sh m a n i a si s, Ly me d i s e a s e a nd schistosomiasis — result from infec- tions transmitted via blood-feeding organisms, such as f leas, mosquitos and ticks. Rising global temperatures can impact zones these arthropods inhabit, Dr. Myers notes. "In East Africa, we're seeing malaria move higher in a ltitude — into the mounta ins — as globa l mea n tem- peratures have been wa rming a s a consequence of climate change …," he says. "We know mosquitos are sensitive to temperatures. Not only does [tem- perature] create a boundary condition within which [mosquitos] exist, it also changes their reproductive rates, biting rates and the rates of reproduction of the parasites inside them. The malaria parasites can all change if tempera- tures are warm. They're sensitive to precipitation and ground moisture, so precipitation patterns will alter the abundance of vectors." Malaria is the most deadly vector- b or ne d isea se, k i l l i ng more t h a n 1.2 million people annually, accord- ing to the W HO, and encountering t he disea se at higher elevations is only one effect of land-use change on its prevalence. M A K I N G CO N N EC TI O N S WHILE CONCERNS ABOUT emerging diseases and food scarcity are often consigned to poor or remote parts of the world, developed countries should take note. Steven Soderbergh's 2011 film Contagion, depicted a pandemic fueled by global connectivity. However, the potential for transoceanic travel and other forms of international contact to facilitate devastating transmission of emerging diseases is not merely the stuff of fiction. Kris Murray, PhD, senior research scientist at EcoHealth Alliance, explains that West Nile virus exemplifies the connectivity of cosmopolitan areas, such as New York City. "If a disease does manage to spill over into the human population and start to circulate, there's actually a really good chance that it will make it to New York City. Even for diseases that are not necessarily spread by people, this may be true, due to the enormous volume and diversity of traded goods that come through. In some cases, the first case of an exotic disease may even be noticed in New York before anywhere else. West Nile virus is an example." M D N E W S . CO M ■ MD NEWS Minnesota | 2 5

• Cover