A woman suspected to be suffering from
cholera is transported in a wheelbarrow
to a treatment clinic in Harare,

Scientists Assess the Future of Infectious Diseases

January 04, 2009 08:01 AM
by Jen O'Neill
Environmental and climate changes thwart progress in the global war against infectious diseases.

Changes in Climate Boost Infectious Diseases

The return of “old world” diseases such as cholera and malaria, coupled with new emerging diseases, sheds light on the impact changes in environmental and climate conditions will have on the future of infectious diseases, scientists say.

“On average, the past three decades have seen the emergence of one new disease a year,” Dr. Julie Hall, communicable diseases expert with the World Health Organization, told ScienceAlert. “[B]ut the incidence of new events is rising.”

Factors including “climate change, along with increasing populations, overuse of antibiotics and global trade and travel, can affect both the likelihood of a new disease emerging and the opportunity for diseases to spread to new populations,” ScienceAlert reported in December.

However, scientists are focused on evaluating disease patterns and how they might manifest in the future. According to Dr. Stephen Prowse of the Australian Biosecurity CRC, “It is not a lack of data that is the problem. Rather, we have so much information to sift through that it is difficult to manage.”

In the meantime, scientists and researchers have only scratched the surface in their understanding of the complex nature of infectious diseases and how they rapidly reach epidemic proportions.

Background: How infectious diseases spread

Anthony S. Fauci, Director of the National Institute of Allergy and Infectious Diseases (NIAID), points out that there are “common determinants of disease emergence” such as poverty, international trade and climate changes.

To better understand and predict disease emergence, Dr. David Morens, also of NIAID, explains that research should be aimed at understanding infectious diseases and how microorganisms that cause disease travel from animals to humans.

NIAID research links urbanization, increased international travel, climate and the growth of drug-resistant microbes as factors that combine to produce new epidemics.

Opinion & Analysis: Infectious disease: a moving target

Climate change is considered a primary culprit in spreading pathogens, health experts from the Wildlife Conservation Society assert. Rainfall helps waterborne diseases, such as cholera, spread “into new regions as a result of climate change, with potential impacts to both human and wildlife health and global economies.”

A recent report called, “The Deadly Dozen: Wildlife Diseases in the Age of Climate Change,” demonstrates how diseases can spread as a result of changes in temperatures and precipitation levels.

According to the report’s authors, monitoring wildlife is an important factor in detecting how such diseases are transmitted.

“The health of wild animals is tightly linked to the ecosystems in which they live and influenced by the environment surrounding them, and even minor disturbances can have far reaching consequences on what diseases they might encounter and transmit as climate changes,” Dr. Steven Sanderson of the Wildlife Conservation Society was quoted as saying by Newswise Science News.

While monitoring efforts have focused on wildlife pathogens, there’s very little existing data on how climate change influences the spread of diseases.

“Monitoring efforts for these diseases need to be examined in tandem with meteorological data to uncover climate-related trends,” Innovations Report says.

Related Topic: Hidden infections

The onset of infectious disease outbreaks has left many researchers perplexed. For instance, it’s actually quite difficult to become gravely ill with cholera. According to a University of Michigan report, “it takes 100 billion bacteria to cause severe illness when ingested with water; 100 million when taken in with food.”

In places like Bengal, where the disease had been prevalent for years, cholera has infected thousands of people but they have not yet become ill.

Aaron King, assistant professor of ecology and evolutionary biology, studied cholera in Bengal and found that as the disease spreads, many people develop a short-lived immunity. However, once large numbers of people are immune, the epidemic lies dormant.

“But before the year is out, they’re susceptible again,” King said, and the cycle starts again. “In order to understand how to control this disease, we really need to understand what's going on in the bulk of cases, not just what's happening in the most severe,” he added.

Until recently, most cholera epidemic studies have focused on only those who are infected with severe cholera.

“The new model raises the possibility that current vaccines could be given at the beginning of cholera season to squelch an incipient epidemic,” University of Michigan News Service reports.

Reference: Health Web Guide


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