Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Higher temperatures helped new strain of West Nile virus spread

30.06.2008
Findings help explain spread of virus strain responsible for largest US epidemics

Higher temperatures helped a new strain of West Nile virus invade and spread across North America, according to a study published in the June 27 issue of the journal PLoS Pathogens.

"The study shows that the warmer the temperature, the greater the advantage of the new strain. It also indicates that increases in temperatures due to global climate change would have major effects on transmission of the virus," said A. Marm Kilpatrick, first author of the paper and a senior research scientist for the Consortium for Conservation Medicine.

Kilpatrick, now an assistant professor of ecology and evolutionary biology at the University of California, Santa Cruz, joined with Laura Kramer and others at the New York State Department of Health's Wadsworth Center to conduct the study, which examined the effects of different temperatures on the transmission of two strains of West Nile virus.

The first occurrence of West Nile virus in North America was in New York City in 1999, when it caused a die-off of crows and other birds and 62 reported cases of human infections, including 7 deaths. In the two years after the introduction of the virus, the rate of transmission was relatively low. As it spread along the Atlantic seaboard, there were only 21 reported human cases in 2000 and 66 in 2001.

In 2002, however, a new strain of the virus emerged and rapidly spread throughout North America, completely displacing the old strain by 2005. Coincident with the spread of this new strain were two of the largest epidemics of West Nile virus recorded to date in North America, with 4,582 cases reported in 2002, 11,356 cases in 2003, and more than 270 deaths in both years. Since then, the number of reported cases per year has ranged from 2,500 to nearly 6,000, with more than 100 deaths each year.

Kilpatrick and Kramer set out to determine how the new strain of West Nile virus had displaced the first strain, and what effect temperature had on transmission by mosquitoes. They used laboratory tests to determine how soon mosquitoes are capable of transmitting the virus after feeding on infected blood. The results showed that the new strain is more efficiently transmitted than the older strain, and the advantage of the new strain increases with higher temperatures.

For both strains, increases in temperature greatly accelerated transmission by increasing the efficiency of viral replication in the mosquitoes. As a result, temperature increases of just a few degrees due to global warming could sharply accelerate transmission of the virus and possibly lead to more severe epidemics of West Nile virus in some cooler regions, Kilpatrick said. The researchers used the results to develop a model to predict the impact of increasing temperatures on West Nile virus transmission by mosquitoes.

"A previous study in our lab demonstrated that the new strain of the virus was more efficient at replicating in mosquitoes, which may have increased the intensity of epidemics in the field," Kramer said. "We wanted to examine whether temperature might have played a role in the invasion of the new strain, and whether its success may have been related to increasing temperatures."

Kramer's lab performed a series of studies that involved infecting one group of mosquitoes with the introduced 1999 strain of West Nile virus and siblings with the recently evolved strain. After holding the mosquitoes at different temperatures and for different lengths of time, researchers determined what fraction could transmit the virus. They found that the new strain was more efficient than the introduced strain at nearly all temperatures and time points after infection.

Kilpatrick, who analyzed the data and developed models to predict the impact of temperature on transmission, said the results provide a striking example of how climate and evolution can interact to increase the transmission of this virus. "These results also suggest that relatively small increases in temperature can have large impacts, due to the nonlinear acceleration of transmission with temperature," he said.

"This study shows how direct the impacts of climate change could be for us all," said Peter Daszak, executive director of the Consortium for Conservation Medicine, based at Wildlife Trust in New York. "It isn't just about a rise in sea level or the melting of a glacier in Alaska--it's about our health and our welfare."

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu
http://www.conservationmedicine.org

More articles from Ecology, The Environment and Conservation:

nachricht Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

IHP presents the fastest silicon-based transistor in the world

05.12.2016 | Power and Electrical Engineering

InLight study: insights into chemical processes using light

05.12.2016 | Materials Sciences

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>