Tag: Thomas B. Fomby

Dallas Morning News: Study: Mild winter, wet spring to blame for Dallas County’s deadly West Nile outbreak

Post author By Margaret Allen
Post date July 17, 2013

A plane flew over central Dallas as part of aerial spraying efforts last summer to combat mosquitoes carrying the West Nile virus. (Credit: Dallas Morning News)

The Dallas Morning News covered the research of SMU economist Thomas B. Fomby and SMU Dedman College Distinguished Alumnus Robert W. Haley, who co-authored a new study on West Nile Virus.

Fomby and Haley, along with other researchers, analyzed a decade of data related to West Nile Virus and, in particular, the 2012 West Nile epidemic in Dallas County. The analysis allowed them to identify important precursors of West Nile Virus outbreaks that allow for early and effective intervention.

Fomby, a data modeling expert, is a professor of Economics and director of the Richard B. Johnson Center for Economic Studies at SMU.

Haley is chief of Epidemiology and professor of Internal Medicine at UT Southwestern. Other authors of the study were physician Wendy Chung, chief epidemiologist, and her associates Christen Buseman, Sibeso Joyner and Sonya Hughes, all of Dallas County Health and Human Services; and James Luby, professor of internal medicine in the Division of Infectious Diseases at UT Southwestern.

They reported the findings in the July 17 issue of The Journal of the American Medical Association.

Their analysis of the West Nile data, along with weather and housing data, found that the epidemics begin early, after unusually warm winters; are often in similar geographical locations; and are predicted by an index based on an estimate of the average number of West Nile virus-infected mosquitoes collected per trap-night, called the Mosquito Vector Index.

As a result of their data analysis, the researchers recommend the use of a vector-index rating system to identify the best timing and location of early interventions.

Read the full story.

EXCERPT:
By Sherry Jacobson
Dallas Morning News

An in-depth study of last year’s West Nile epidemic in Dallas County blames a mild winter, wet spring and an abundance of mosquitoes for spreading the sometimes-fatal virus.

But local officials did not realize how quickly the mosquito-borne outbreak was unfolding. If they had recognized the signs earlier, 110 severe human infections might have been prevented and a dozen lives saved, the study said.

“It’s a very optimistic estimate and might not be totally realistic,” said Dr. Robert Haley, one of the authors of the study published Wednesday in the Journal of the American Medical Association.

His estimate was based on the possibility that officials could have resorted to aerial spraying of insecticides in early July, instead of a month later. It also supposed that spraying could have halted the West Nile outbreak.

The study suggested a deadly equation was at work: Five percent of the Culex mosquitoes were carrying the West Nile virus by late June. At that point, the disease was spreading quickly, but no one knew it.

While the conclusions are purely hindsight, the study could provide valuable information to help prevent future West Nile outbreaks, said Haley, chief epidemiologist at UT Southwestern Medical Center.

“This could be a breakthrough for how to track a West Nile outbreak,” he said. “For a small amount of data, this study is remarkably strong.”

The study grew out of the worst West Nile outbreak in Texas history. More than 400 Dallas County residents suffered mild to severe symptoms of the neuroinvasive disease and 20 died.

All were bitten by infected mosquitoes despite widespread warnings and ground spraying of insecticide. But no one could explain why it happened.

Dr. Wendy Chung, the study’s lead author, said researchers looked for answers in a massive amount of West Nile data collected last year by government agencies.

The study focused on infected mosquitoes and how quickly they passed the virus to humans. It also considered the locations where people were infected and if weather patterns might have accelerated the outbreak.

“Weather that predisposes us to have a bad West Nile season is considered one of the soft indicators” of an impending outbreak, said Chung, chief epidemiologist for Dallas County Health and Human Services. “You can have bad weather and not have a bad season.”

Read the full story.

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Tags Dedman College, Robert W. Haley, SMU Department of Economics, Thomas B. Fomby

Earth & Climate Economics & Statistics Health & Medicine Plants & Animals Researcher news

Mosquito indexing system identifies best time to act against potential West Nile Virus outbreaks

Post author By Margaret Allen
Post date July 16, 2013

Study examines characteristics, features of West Nile virus outbreaks from Dallas County housing, hospital and weather data

Larvae of Culex Mosquitoes make dense groups in standing water. (Credit: James Gathany, CDC)

Researchers who analyzed a decade of data related to West Nile Virus and, in particular, the 2012 West Nile epidemic in Dallas County, have identified important precursors of West Nile Virus outbreaks that allow for early and effective intervention.

An analysis of the West Nile data, along with weather and housing data, found that the epidemics begin early, after unusually warm winters; are often in similar geographical locations; and are predicted by an index based on an estimate of the average number of West Nile virus-infected mosquitoes collected per trap-night, called the Mosquito Vector Index.

As a result of their data analysis, the researchers recommend the use of a vector-index rating system to identify the best timing and location of early interventions.

The researchers, from Southern Methodist University, UT Southwestern Medical Center and Dallas County Health and Human Services, reported the findings in the July 17 issue of The Journal of the American Medical Association.

The analysis revealed a mosquito vector index rating of 0.5 in June or July as the best time to act to avoid an outbreak and stave off the resultant rise in human West Nile infections, which can cause long-term neurological damage and even death.

“In years when the vector index didn’t start up until late July or August, impending outbreaks just sputtered — in late summer mosquito abundance declines and mosquitoes become less active and stop biting as much. When the vector index goes above .5 early — June or July — right then large numbers of people are silently getting infected, and this should be the best time to intervene,” said senior author Robert W. Haley, Chief of Epidemiology and Professor of Internal Medicine at UT Southwestern.

“After the infecting mosquito bite, on average it takes a week for the first symptoms to develop, a week to see people turning up at hospitals, and a week for laboratory confirmation of the diagnosis and reporting to health officials,” Haley said. “That three weeks is critical. Acting early from the vector index rather than after human case reports and deaths mount up can nip an outbreak in the bud. However, if mosquito data are unavailable or consensus to intervene takes longer, later intervention may still be important to terminate the outbreak.”

The analysis found also that less of a hard freeze during winter months and unusually warm spring temperatures contributed to epidemic years for West Nile, a major concern as global temperatures continue to warm, Haley said.

A fourth critical finding in the paper related census track data to the 2012 outbreak, showing that areas of higher property values, higher housing density, and higher percentages of unoccupied homes were at higher risk. That’s likely due to fostering the types of environment and mosquitos most likely to transmit the disease, which is carried more by house mosquitoes than wooded mosquitoes. In Dallas County, the data showed year-after-year clustering in the Park Cities and North Dallas areas.

Study authors supply instruction manual for other counties
The analysis tools used in the study may be applicable elsewhere, but due to variations in weather, mosquito populations and other factors, each region or county will need to conduct its own analysis to identify the most appropriate vector index rating signaling when to act, Haley said. Along with the paper, the authors provide an instruction manual for other counties to calculate the vector index from their own mosquito infection surveillance data.

“Given the leading character of this index, epidemiologists and government officials can implement, in a more timely manner, preventative measures to reduce the impact of future West Nile Virus outbreaks,” said data modeling expert Thomas B. Fomby, Professor of Economics and the Director of the Richard B. Johnson Center for Economic Studies at SMU.

Fomby provided the time series expertise needed to analyze the leading nature of the vector index and determine that aerial spraying used during the epidemic did not have any significant adverse health effects on the general public.

“Time Series Count modeling and Event Analysis are statistical methods that are frequently used in economic research but not so often used in medical research,” Fomby said. “Time Series Count modeling was used to investigate the leading nature of the vector index while Event Analysis was used to examine the impacts of aerial spraying. This is a prime example of where interdisciplinary tools can be useful in conducting scientific research.”

Other authors of the study were physician Wendy Chung, Chief Epidemiologist, and her associates Christen Buseman, Sibeso Joyner and Sonya Hughes, all of Dallas County Health and Human Services; and James Luby, professor of internal medicine in the Division of Infectious Diseases at UT Southwestern.

West Nile virus first identified in Dallas County in 2002
“After declining over the prior 5 years, mosquito-borne West Nile virus infection resurged in 2012 throughout the United States, most substantially in Dallas County, Texas. Dallas has been a known focus of mosquito-borne encephalitis since 1966, when a large epidemic of St. Louis encephalitis (SLE) occurred there, necessitating aerial spraying of insecticide for control,” according to background information in the article.

“With the introduction of West Nile virus into New York City in 1999 and its subsequent spread across the country, West Nile virus appears to have displaced SLE virus,” the authors wrote. “Dallas recognized its initial cases of West Nile virus encephalitis in 2002 and its first sizeable outbreak in 2006, followed by 5 years of low West Nile virus activity. In the 2012 nationwide West Nile virus resurgence, Dallas County experienced the most West Nile virus infections of any U.S. urban area, requiring intensified ground and aerial spraying of insecticides.”

Study analyzed multitude of data, from infections to weather to geography
The study examined the features associated with the West Nile virus epidemics to identify surveillance and control measures for minimizing future outbreaks.

The researchers analyzed surveillance data from Dallas County (population, 2.4 million), which included the numbers of residents diagnosed with West Nile virus infection between May 30, 2012 and Dec. 3, 2012; mosquito trap results; weather data; and syndromic (pertaining to symptoms and syndromes) surveillance from area emergency departments.

From May 30 through Dec. 3, 2012, patients with any West Nile virus-positive test result were reported to the health department; 615 met laboratory case criteria, and 398 cases of West Nile virus illness with 19 deaths were confirmed by clinical review in residents of Dallas County.

The outbreak included 173 patients with West Nile neuroinvasive disease (WNND) and 225 with West Nile fever, and 17 West Nile virus-positive blood donors. Regarding patients with WNND, 96 percent were hospitalized; 35 percent required intensive care; 18 percent required assisted ventilation; and the case-fatality rate was 10 percent. The overall WNND incidence rate in Dallas County was 7.30 per 100,000 residents in 20l2, compared with 2.91 in 2006.

The first West Nile virus-positive mosquito pool of 2012 was detected in late May, earlier than in typical seasons. Symptoms of the first 19 cases of WNND in 2012 began in June, a month earlier than in most prior seasons; thereafter, the number of new cases escalated rapidly. Sequential increases in the weekly vector index early in the 2012 season significantly predicted the number of patients with onset of symptoms of WNND in the subsequent l to 2 weeks.

West Nile neuroinvasive disease clustered in neighborhoods with high housing density
The 2012 epidemic year was distinguished from the preceding 10 years by the mildest winter, as indicated by absence of hard winter freezes, the most degree-days above daily normal temperature during the winter and spring and other features. During the 11 years since West Nile virus was first identified in Dallas, the researchers found that the annual prevalence of WNND was inversely associated with the number of days with low temperatures below 28 degrees Fahrenheit in December through February.

“Although initially widely distributed, WNND cases soon clustered in neighborhoods with high housing density in the north central area of the county, reflecting higher vector indices and following geospatial patterns of West Nile virus in prior years,” the authors write.

Aerial insecticide spraying was not associated with increases in emergency department visits for respiratory symptoms or skin rash.

“This report identifies several distinguishing features of a large urban West Nile virus outbreak that may assist future prevention and control efforts for vector-borne infections,” the authors write. “Consideration of weather patterns and historical geographical hot spots and acting on the vector index may help prevent West Nile virus-associated illness.” — UT Southwestern, JAMA, SMU

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Tags Dedman College, Robert W. Haley, SMU Department of Economics, Thomas B. Fomby

Culture, Society & Family Economics & Statistics Researcher news

SMU-North Texas Food Bank study will analyze causes of hunger in Dallas and rural North Texas

Post author By Margaret Allen
Post date November 6, 2012

SMU with The Hunger Center of North Texas will look at the impact of social networks and social capital

Economics researchers at SMU will analyze the roles social networks and isolation play in fighting hunger in North Texas.

Recent studies have found that household economic resources are not the only factor contributing to food insecurity, according to SMU economist Thomas B. Fomby.

About 1 in 6 U.S. households are affected by food insecurity, meaning there’s not enough food at all times to sustain active, healthy lives for all family members, according to the U.S. Department of Agriculture.

Reidus hilli, John Graf, SMU, coelacanth, Dipluridae,

“This study will analyze the role of other factors causing food insecurity, such as urban or rural settings, access to nutrition assistance programs, access to inexpensive groceries, family support and social stigma,” Fomby said.

Fomby, professor of economics and director of the Richard B. Johnson Center for Economic Studies, and Daniel Millimet, SMU professor of economics, are conducting the study. A $120,000 grant from the North Texas Food Bank is funding the research. The study will be complete in March 2014.

Household income a powerful predictor, but social networks play role
Although household income is the single most powerful predictor of food security, poverty and hunger are not synonymous. According to Feeding America, 28 percent of food insecure residents in Dallas County are ineligible for most nutrition assistance programs because they have incomes above 185 percent of the federal poverty level; and the U. S. Department of Agriculture reports that 58.9 percent of U.S. households with incomes below the poverty level are food secure. The reasons for this are not well understood.

“With this research, we expect to better understand the causes of food insecurity in North Texas and improve the assessment of at-risk households,” Fomby said.

The SMU study is one of two major research projects launching The Hunger Center of North Texas, a new collaborative research initiative created by the North Texas Food Bank. The University of North Texas is also collaborating on a study.

The studies will focus on the impact that “social networks” and “social capital” have on household food security. The central questions are:

How do social relationships and community conditions make it easier (or harder) for low-income households to keep healthy food on the table?
How do these social and community influences differ in the City of Dallas and rural areas of North Texas?

Groundbreaking research may help leverage social forces to reduce food assistance
“We believe that this research will be groundbreaking,” said Richard Amory, director of research for the North Texas Food Bank. “Nutrition assistance programs tend to approach individuals and households in isolation. Understanding the role that communities play in food security may help us leverage social forces to develop more effective programs and, ultimately, reduce the need for food assistance.”

The studies will start to shed some light on issues related to hunger in the community, said Kimberly Aaron, vice president of Policy, Programs and Research for the North Texas Food Bank.

“In performing our due diligence on existing research, while forming The Hunger Center, it became clear that many factors related to food insecurity are not well understood,” Aaron said.

SMU and the North Texas Food Bank recently formed a partnership, “Stampede Against Hunger,” to build on SMU’s strong support for NTFB, connecting campus groups already working with the food bank, as well as encouraging new types of participation for the campus and alumni community.

SMU support for the food bank has ranged from traditional food drives and volunteer work in the NTFB distribution center, to research for the food bank conducted by students in the Cox School of Business and the Bobby B. Lyle School of Engineering. Faculty and students from the Annette Caldwell Simmons School of Education and Human Development volunteer regularly in NTFB nutrition courses and Fondren Library staff organize a “Food for Fines” drive each year, waiving library fines in exchange for donations of non-perishable food items.

Fomby and Millimet are in the SMU Department of Economics in Dedman College. — Nancy George, and the NTFB

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Tags Annette Caldwell Simmons School of Education and Human Development, Bobby B. Lyle School of Engineering, Cox School of Business, Daniel L. Millimet, Dedman College, Fondren Library, Richard B. Johnson Center for Economic Studies, SMU Department of Economics, Thomas B. Fomby

Economics & Statistics Health & Medicine

Study: Antibiotics, instead of emergency surgery, may better treat cases of nonperforating appendicitis

Post author By Margaret Allen
Post date April 26, 2011

Findings suggest that nonperforating appendicitis, when the appendix hasn’t burst, and nonperforating diverticulitis could be similar diseases that warrant similar treatments

Antibiotics rather than surgery may be the better treatment for cases of appendicitis in which the appendix hasn’t burst, according to a new study.

The study’s authors say the findings suggest that nonperforating appendicitis, as the disease is called when the appendix hasn’t burst, may be unrelated to perforating appendicitis, in which the appendix has burst.

Instead, the study found that nonperforating childhood appendicitis, which historically has been treated with emergency surgery, seems to be a disease similar to nonperforating adult diverticulitis, which is often treated with antibiotics.

“It is assumed, but has never been proved, that appendicitis always perforates unless appendectomy is performed early in its course,” said the authors. “There is a growing body of evidence to suggest that this is not the case.”

The study, “Epidemiological similarities between appendicitis and diverticulitis suggesting a common underlying pathogenesis,” was reported in the Archives of Surgery.

Hospital discharge records reveal correlation
Childhood appendicitis and adult diverticulitis share many similarities, including association with colon hygiene and a low intake of fiber in the diet.

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Those shared epidemiological features prompted researchers to examine whether the two might be similar, according to economist Thomas B. Fomby at Southern Methodist University in Dallas.

A statistical sampling of data from U.S. hospital discharge records revealed a correlation between nonperforating appendicitis and nonperforating diverticulitis.

“We used a technique called cointegration to investigate common movements in epidemiologic data series,” said Fomby, a professor in SMU’s Department of Economics, who led the statistical analysis with statistician Wayne A. Woodward, professor and department chair in SMU’s Department of Statistical Science.

Lead author on the study was Edward H. Livingston, M.D., in the division of Gastrointestinal and Endocrine Surgery at University of Texas Southwestern Medical School, Dallas; with the Department of Surgery, Veterans Affairs Medical Center Dallas; and in the Department of Bioengineering, University of Texas at Arlington. Also co-authoring was Robert W. Haley, M.D., in the Department of Internal Medicine-Epidemiology, UT Southwestern Medical School, and a past recipient of the SMU Distinguished Alumni Award.

Regional and national data move together over time
The study looked at 27 years of data from the National Hospital Discharge Survey, which is compiled annually by the Centers for Disease Control and Prevention. The analysis specifically compared national data and regional data for children with appendicitis and adults with diverticulitis who were admitted to U.S. hospitals between 1979 and 2006.

The statistical methodology called panel cointegration allowed the researchers to sift through eight different combinations of the two diseases, both by region and nationally, to see whether they vary together across time and to eliminate the possibility of coincidence or a chance correlation, Fomby said.

“We analyzed all the national data, and then found the same thing in every region also,” Fomby said. “That reinforced what we were finding at the national level.”

The authors’ analysis shows that although the annual incidence rates of adult nonperforating diverticulitis and child nonperforating appendicitis changed greatly during the past 25 years, their secular patterns — long-term trends — followed the same general patterns, overall as well as region by region, according to the authors.

“These secular changes were significantly cointegrated, meaning that the incidence rates changed in time together, suggesting that nonperforating appendicitis and nonperforating diverticulitis could be different manifestations of the same underlying process.”

Statisticians and economists have applied this kind of analysis to international finance, macroeconomics and other areas, but it’s not been used to any extent in medical epidemiology, Fomby said. Two economists, Clive Granger and Robert Engel, won the 2003 Nobel Prize in Economics for their invention of the technique.

Appendicitis, diverticulitis may be similar diseases
“Childhood appendicitis and adult diverticulitis seem to be similar diseases, suggesting a common underlying pathogenesis,” write the authors. Secular trends for the nonperforating and perforating forms are strikingly different, they said.

“At least for appendicitis, perforating disease may not be an inevitable outcome from delayed treatment of nonperforating disease. If appendicitis represents the same pathophysiologic process as diverticulitis, it may be amenable to antibiotic rather than surgical treatment.”

Appendicitis is a painful infection in the area of the lower right abdomen that typically affects younger people, age 10 to 30, according to the National Digestive Diseases Information Clearinghouse within the National Institutes of Health. It is the No. 1 cause of emergency abdominal surgeries, according to NDDIC.

Appendicitis is caused by blockage in the appendix, a fingerlike pouch jutting from the large intestine, according to NDDIC. Among the various causes of the blockage can be feces, abdominal trauma or inflammatory bowel disease, the agency says.

Diverticulitis, which is more common among people older than 60, occurs when pouches that have developed in the lining of the gastrointestinal tract become inflamed and sometimes infected, according to NDDIC. It is often treated with antibiotics, the authors say.

Perforating appendicitis not a progression of nonperforating appendicitis?
“These findings seem incompatible with the long-held view that perforating appendicitis is merely the progression of nonperforating disease where surgical intervention was delayed too long,” write the authors. “If perforating appendicitis was simply a manifestation of nonperforating appendicitis not treated in a timely manner, the secular trends should have been statistically similar, which they were not.”

Both diseases have increased in incidence as cleanliness in the Western world has improved, in populations with higher socioeconomic status, and where grain-processing technologies have lowered dietary fiber content, the authors say.

In a previous study, the researchers demonstrated changes in the annual incidence rates of appendicitis. The new study demonstrated changes for nonperforating diverticulitis as well. — Margaret Allen

SMU is a private university in Dallas where nearly 11,000 students benefit from the national opportunities and international reach of SMU’s seven degree-granting schools. For more information see www.smu.edu.

Tags Dedman College, SMU Department of Economics, SMU Department of Statistical Science, Thomas B. Fomby, Wayne A. Woodward

Economics & Statistics Health & Medicine Researcher news SMU In The News

Appendicitis linked to flu-like virus outbreaks

Post author By Margaret Allen
Post date January 20, 2010

The research of SMU faculty Thomas B. Fomby and Wayne A. Woodward has been published in the January issue of the journal Archives of Surgery. Fomby is a professor and chairman of the Department of Economics and Woodward is a professor in the Department of Statistical Science.

The research described in the article “Association of Viral Infection and Appendicitis” looks at the relationship between appendicitis and seasonal viral infections. The scientists reviewed 36 years of hospital discharge data and concluded there is a relationship to a flu-like virus.

Fomby and Woodward collaborated with researchers from UT Southwestern Medical Center in Dallas and the VA Medical Center in Gainesville, Florida.

Articles about the results of the research have been widely published on many science and research news sites, including Daily Mail Online, USA Today, Business Week, Science Daily, Physorg.com, Health News Digest, BioScience Technology, Newswise and many others.

EXCERPT:

Appendicitis may be triggered by a viral infection

By JENNY HOPE
Daily Mail Online
A viral infection could explain why appendicitis appears more common in certain years and during the summer.

A flu-like virus could be the hidden cause of appendicitis, scientists claim.

Although one in ten of us will experience the condition — in which the appendix becomes dangerously inflamed — doctors have always been baffled by what triggers it.

A viral cause would fit in with another of the researchers’ findings — that appendicitis appears to be more common in certain years and during the summer.

The illness occurs when the appendix, a worm-like cul-de-sac connected to the colon on the right side of the body, becomes inflamed.

A perforated appendix that has swollen and burst is life-threatening because the abdomen is filled with infected material. In fact, appendicitis is the most common reason for emergency surgery.

In the latest study, researchers examined American hospital admissions for appendicitis, influenza and gastric viral infections over 36 years.

Their analysis showed appendicitis peaked in the years 1977, 1981, 1984, 1987, 1994 and 1998.

That clustering pattern suggested outbreaks were typical of viral infections.

Seasonal trends were also uncovered, showing a slight increase in the number of appendicitis cases over the summer months.

Read the full story.

Tags Dedman College, SMU Department of Economics, SMU Department of Statistical Science, Thomas B. Fomby, Wayne A. Woodward

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Study examines characteristics, features of West Nile virus outbreaks from Dallas County housing, hospital and weather data

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Findings suggest that nonperforating appendicitis, when the appendix hasn’t burst, and nonperforating diverticulitis could be similar diseases that warrant similar treatments

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Appendicitis may be triggered by a viral infection