STOPPING EBOLA: NSF FUNDS RESEARCH ON STOPPING EBOLA

FROM:  NATIONAL SCIENCE FOUNDATION 

Halting the spread of Ebola: Nigeria a model for quick action, scientists find

Rapid control measures critical to stopping the virus in its tracks

Ebola. The word brings fear of an unseen and potentially lethal enemy. But there are ways to stop its spread, say infectious disease scientists.

Quick intervention is needed, according to the researchers, who recently published their findings in the journal Eurosurveillance.

Analyzing Ebola cases in Nigeria, a country with success in containing the disease, the scientists estimated the rate of fatality, transmission progression, proportion of health care workers infected, and the effect of control interventions on the size of the epidemic.

Rapid response needed

"Rapid control is necessary, as is demonstrated by the Nigerian success story," says Arizona State University (ASU) scientist Gerardo Chowell, senior author of the paper.

"This is critically important for countries in the West Africa region that are not yet affected by the Ebola epidemic, as well as for countries in other regions of the world that risk importation of the disease."

The research is funded by the U.S. National Science Foundation (NSF)-National Institutes of Health (NIH)-Department of Agriculture (USDA) Ecology and Evolution of Infectious Diseases (EEID) Program.

"Controlling a deadly disease like Ebola requires understanding how it's likely to spread, and knowing the ways of managing that spread that are most likely to be effective," says Sam Scheiner, NSF EEID program director.

"Being able to respond quickly needs a foundation of knowledge acquired over many years. The work of these scientists is testimony to long-term funding by the EEID program."

Control measures in Nigeria

The largest Ebola outbreak to date is ongoing in West Africa, with more than 8,000 reported cases and 4,000 deaths. However, just 20 Ebola cases have been reported in Nigeria, with no new cases since early September.

All the cases in Nigeria stem from a single traveler returning from Liberia in July.

The study used epidemic modeling and computer simulations to project the size of the outbreak in Nigeria if control interventions had been implemented during various time periods after the initial case, and estimated how many cases had been prevented by the actual early interventions.

"This timely work demonstrates how computational simulations, informed by data from health care officials and the complex social web of contacts and activities, can be used to develop both preparedness plans and response scenarios," says Sylvia Spengler, program director in NSF's Directorate for Computer and Information Science and Engineering, which also supported the research.

Control measures implemented in Nigeria included holding all people showing Ebola symptoms in an isolation ward if they had had contact with the initial case. If Ebola was confirmed through testing, people diagnosed with the disease were moved to a treatment center.

Asymptomatic individuals were separated from those showing symptoms; those who tested negative without symptoms were discharged.

Those who tested negative but showed symptoms--fever, vomiting, sore throat and diarrhea--were observed and discharged after 21 days if they were then free of symptoms, while being kept apart from people who had tested positive.

Brief window of opportunity

Ebola transmission is dramatically influenced by how rapidly control measures are put into place.

"Actions taken by health authorities to contain the spread of disease sometimes can, perversely, spread it," says NSF-funded scientist Charles Perrings, also of ASU.

"In the Nigeria case, people who tested negative but had some of the symptoms were not put alongside others who tested positive," says Perrings. "So they had no incentive to flee, and their isolation did nothing to increase infection rates. Elsewhere in the region isolation policies have had a different effect."

The researchers found that the projected effect of control interventions in Nigeria ranged from 15-106 cases when interventions are put in place on day 3; 20-178 cases when implemented on day 10; 23-282 cases on day 20; 60-666 cases on day 30; 39-1,599 cases on day 40; and 93-2,771 on day 50.

The person who was initially infected generated 12 secondary cases in the first generation of the disease; five secondary cases were generated from those 12 in the second generation; and two secondary cases in the third generation.

That leads to a rough estimate of the reproduction number according to disease generation declining from 12 during the first generation, to approximately 0.4 during the second and third disease generations.

A reproductive number above 1.0 indicates that the disease has the potential to spread.

Recent estimates of the reproduction number for the ongoing Ebola epidemic in Sierra Leone and Liberia range between 1.5 and 2 (two new cases for each single case), indicating that the outbreak has yet to be brought under control.

The effectiveness of the Nigerian response, scientists say, is illustrated by a dramatic decrease in the number of secondary cases over time.

The success story for Nigeria, they maintain, sets a hopeful example for other countries, including the United States.

Co-authors of the Eurosurveillance paper are Gerardo Chowell, Arizona State University; Folorunso Oludayo Fasina, University of Pretoria, South Africa; Aminu Shittu, Usmanu Danfodiyo University, Nigeria; David Lazarus, National Veterinary Research Institute, Plateau State, Nigeria; Oyewale Tomori, Nigerian Academy of Science, University of Lagos, Lagos, Nigeria; Lone Simonsen, George Washington University, Washington, D. C.; and Cecile Viboud, National Institutes of Health, Bethesda, Md.

-- Cheryl Dybas, NSF (
-- Julie Newberg, ASU
Related Programs
Ecology and Evolution of Infectious Disease

THE BOBCAT AND HUMAN INFECTIOUS DISEASE CONNECTION

Credit:  Wikimedia/NSF

FROM: NATIONAL SCIENCE FOUNDATION
Cool Cat in a Hot Zone

November 5, 2012
What do Ventura County, Calif., and the Front Range of Colorado's Rocky Mountains have in common?

Ventura, which encompasses the city of Los Angeles, has a Mediterranean climate and habitat; the Front Range surrounding Denver is cooler, drier and is lined with tall conifers instead of low, dense shrubs.

Both, however, have people. Lots of them.

But it's what else they have in common that tells the real tale of these urban areas.

Alley cat of the wild
It's on the move from three hours before sunset until midnight, and again before dawn ‘til three hours after sunrise. Each night it roams two to seven miles, mostly along the same route.

Like humans, it visits known locales along the way. In this case, though, those places are a hollow log or two, a brush pile or thicket and the underside of a rock ledge.

It also shares something far more personal with the people it quietly lives alongside: gastrointestinal diseases.

It's a bobcat, and we gave it our afflictions rather than the other way around, say scientists Sue VandeWoude, Kevin Crooks, Mike Lappin and Andrea Scorza of Colorado State University at Fort Collins; Scott Carver of the University of Tasmania; Sarah Bevins of the U.S. Department of Agriculture and Seth Riley of the U.S. National Park Service.

The researchers published results of their study of the parasites bobcats and humans share in a recent issue of the Journal of Clinical Microbiology.

Their work is funded by the joint National Science Foundation (NSF) and National Institutes of Health (NIH) Ecology and Evolution of Infectious Diseases (EEID) Program.

"The growing interaction of humans and wildlife means that we now share our diseases with each other at an ever-increasing rate," says Sam Scheiner, EEID program officer at NSF.

NSF's EEID program is funded by the agency's Division of Environmental Biology and Division of Ocean Sciences.

"This study demonstrates that we and our wild animal neighbors," says Scheiner, "are closely interconnected in ways that affect the health of us all."

The spillover effect
Pathogen spillover, as it's known, is a major source of disease in humans and in wildlife.

Indeed, bobcats are more likely to pick up parasites such as Giardia when the cats are closer to urban areas, VandeWoude and colleagues found.

They collected bobcat fecal samples in Ventura County and on the Front Range and tested them for Toxoplasma gondii, Giardia duodenalis and Cryptosporidium spp. All are disease-causing parasites found in wildlife and in people. Contact with the latter two results in diarrhea and other gastrointestinal upsets.

The scientists compared samples from bobcats in the two urban areas with those from rural areas of Colorado.

The findings show that city bobcats are more likely than country bobcats to carry parasites.

"Bobcats are exposed to and shed more zoonotic [i.e., may be transmitted between species] parasites near human-occupied landscapes," says Crooks.

But how did the cats, which are smaller relatives of threatened Canadian lynx, acquire the parasites?

"They were probably exposed to the water supply around cities," says VandeWoude. Parasites all-too-often lurk there.

Cryptosporidium parvum and Giardia duodenalis account for the majority of waterborne disease outbreaks in humans, with hundreds of thousands of cases in the United States alone every year.

Studies have long suggested that wild cats such as bobcats might contribute to a spillover of pathogens to humans, and vice-versa. But with the cats' secretive natures, few researchers have been able to draw conclusions about wild cats' "shedding" of disease-causing microbes. This study is the first.

A disease continuum
Bobcats are widespread in North America. They traverse a continuum of natural to urbanized habitats, often living side-by-side with humans, domestic animals and other urban-adapted wildlife species.

"Along these boundaries," says VandeWoude, "close living quarters make it easy for one species to transmit diseases to another."

In a city or suburb, pathogens travel from human to bobcat, and bobcat to human, the scientists found, almost as fast as a virus that infects one human family member runs through an entire household.

Whether that household lives in a two-story A-frame or a two-story log pile, there's not much difference, it turns out, in the spread of diseases.

It must be something in the water
It's when everyone heads for the water that things really begin to ramp up.

One group of bobcats in Ventura County, says Carver, the paper's lead author, left its calling card in the Malibu Creek watershed: Cryptosporidium and Giardia. Malibu Creek's environs are heavily populated by bobcats--and humans.

"Our results suggest that humans transmitted these pathogens to bobcats," says Carver, "likely through contaminated water or other environmental sources."

At the time of the study, there was no evidence that bobcats carrying the parasites were ill. But for these cool cats that roam along our streets and through our backyards, life in the ‘burbs can be a chancy existence. Simply crossing an urban stream may be walking through a hot zone.

For bobcats. And for humans.

Cheryl Dybas, NSF