Thomas D. Kirsch, M.D., M.P.H., writes in the essay that the team of Johns Hopkins physicians that he lead in Haiti for two weeks soon after the earthquake had to quickly adjust standards of care that are common in the United States due to the sheer volume of patients, the wide range of injuries and complaints, and inadequate medical resources that had to be allocated to those most likely to benefit from them.

Kirsch and his six-member team worked at University Hospital in Port-au-Prince, where they saw on average 350 to 450 patients per day. In the JAMA essay, Kirsch dubs this daily march of the suffering "The Line."

This tide of battered humanity, which began forming some days at 5:30 a.m., Kirsch writes, was "unrelenting in numbers, in illness, in injury, and in heartbreak."

"The Line is a force that never stops its pressure. It is the pressure of the massive imbalance of needs and resources," writes Kirsch and his co-author and wife Margaret Moon, M.D., M.P.H.

As a result of these problems, the authors note, "The standards have to change … The standards get lower, must be lower than anything these clinicians have ever imagined before. We worry about the slippery slope toward inhumane medicine."

The intense experience in Haiti, Kirsch writes, raises many troubling and difficult ethical and moral questions, none of which have easy answers. Kirsch, deputy director of the Johns Hopkins Office of Critical Event Preparedness and Response, is now working with the Johns Hopkins Berman Institute of Bioethics, to host a symposium this fall to explore the ethics of triage and resource-allocation during mass disasters.

The Berman Institute is an independent, interdisciplinary center dedicated to the study of complex moral and medical issues.

Kirsch, a trained medical disaster expert who assisted with medical responses to Hurricane Katrina and the Sept. 11 terrorist attacks in New York, was among the first medical staff sent to Haiti by Johns Hopkins Medicine. He deployed to the country soon after the massive January 12 earthquake, which killed an estimated 230,000 people, as part of the Johns Hopkins Go Team. The multidisciplinary group of approximately of 185 is trained to respond to natural and manmade catastrophes. Moon, a Johns Hopkins pediatrician, did not deploy to Haiti.

Kirsch has been tapped by the nonprofit Earthquake Engineering Research Institute to help assess earthquake building damage in Chile. Kirsch will be looking into how building damage contributed to injuries, deaths and hospital closings in the February 27 earthquake.

New Haven, Conn. — Working memory loss can be reversed using a short-term drug regimen that produces long-lasting effects, a Yale study has found.

Results from this study led by Stacy Castner at Yale School of Medicine may ultimately lead to new treatment strategies for those who have lost working or short-term memory. The team’s past studies suggest that long-term treatment with antipsychotic medications for diseases such as schizophrenia, decrease the number of D1 receptors in cortical neurons. D1 receptors are one of five known dopamine receptors, which control memory function.

Published in the March 17 issue of Science, results from this new study show that long-term treatment with antipsychotic drugs produces memory impairments when the treatment lasts over several months.

“We also found that the memory deficits produced by anti-psychotic drugs can be reversed by stimulating D1 receptors with a D1 agonist-a drug that stimulates mainly D1 receptors,” said Castner, associate research scientist at Yale School of Medicine.

The D1 agonist used in the study was ABT-431, an experimental and not yet available drug which effectively reversed memory loss in six primates. The improvements have been sustained for more than a year.

The return of short-term memory, which is often lost due to age and diseases such as schizophrenia and Parkinson’s, is critical because short-term memory allows individuals to briefly hold information in mind while the knowledge is processed to determine an appropriate action.

It only took a relatively short treatment regimen of 25 days to get a positive effect, and it could be even shorter with the same effect, said Castner. The improvement in memory persisted for months and years after the last treatment, suggesting that the state of the circuitry involved in memory processing had been permanently or semi-permanently restored to a different level of sensitivity.

Castner’s team included Patricia Goldman-Rakic and Graham V. Williams in the section of neurobiology at Yale School of Medicine. The research was supported by Hoechst Marion Rousell (now Aventis Pharmaceuticals); the National Institute of Mental Health; and the National Institute on Drug Abuse.

In an attempt to provide a reliable and trustworthy source for reproductive health information for teenagers, one physician-researcher at Women & Infants Hospital of Rhode Island has launched the website Ask A Doc RI.

"My thought was to bring the information to where the teenagers are, which is on the internet," says Vinita Goyal, MD, MPH, of Women & Infants’ Center for Women’s Primary Care. "Ask A Doc RI contains a variety of information on contraception and local clinical resources where youth can seek health care."

In addition, the website, which includes links to Healthy Kids Rhode Island and Women & Infants, fields anonymous questions on sexual health from teenagers. The questions are answered by one of five participating Women & Infants physicians, and the answers are posted online within 72 hours.

"Our outreach will target teenagers living in Rhode Island communities with high teen pregnancy rates — Providence, Pawtucket, Central Falls and Woonsocket — to get this important information to them," Dr. Goyal explains, noting that information will be available in community health centers and through Healthy Kids Rhode Island coalition members working with underserved youth.

Ask A Doc RI will also serve as a research project for Dr. Goyal, who is Women & Infants’ current Women’s Reproductive Health Research scholar, a program sponsored by the Eunice Kennedy Shriver National Institute of Child Health & Human Development to protect research time for young doctors. There are limited studies specifically addressing the effectiveness of contraceptive education through the internet in promoting healthy behaviors. Confidential surveys will be given to teenagers asking questions on the site and the information will be collected as part of the research.

"Success of the project will be measured by the number of contraceptive queries obtained through the website," Dr. Goyal notes. "While it will be difficult to ascertain if contraceptive behavior is improved, it is expected that if the website serves as a useful educational tool for young women in Rhode Island, the number of queries posted will increase over time."

In addition to fielding questions on Ask A Doc RI, there are sections on the website containing general information on all available contraceptive options and frequently asked questions about contraception, as well as contact information on local health centers for teens interested in making an appointment or meeting face to face with a provider.

Unique to Ask A Doc RI will be a section with current contraceptive issues brought up by local and national media. Complete information will be supplied so teenagers can make the best decision for their sexual health.

"Many young women discontinue contraception over concerns about safety. Incomplete news reports about intrauterine devices, litigious commercials regarding the association of blood clots and oral contraceptive pill use, and other similar events have resulted in young women discontinuing effective methods of contraception without seeking alternative methods to prevent unplanned pregnancy," Dr. Goyal says.

Ask A Doc is sponsored by a grant from the Lalor Foundation, an organization that seeks to educate young women about human reproduction in order to broaden and enhance their options in life.

The new website can be found at www.askadocri.

Oncologists frequently use anthracyclines, including epirubicin and doxorubicin, to treat breast cancer patients. However, the drugs cause lasting heart problems in a substantial number of patients. To limit the problem, current treatment guidelines suggest that patients receive no more than 900 mg/m2 epirubicin over the course of their cancer care.

In the current study, Marianne Ryberg, M.D., of the University of Copenhagen and colleagues followed 1,097 patients with metastatic breast cancer who were treated in a single hospital near Copenhagen between 1983 and 2003. The researchers assessed patients’ risk factors for cardiotoxicity and corrected for the risk of death from all other competing causes of death, including cancer. (The studies that have previously concluded that the upper safe limit of epirubicin is 900 mg/m2 have not generally corrected for other causes of death.) Using these data, they calculated the maximum cumulative dose of epirubicin that is associated with a 5 percent risk of developing heart disease.

Ryberg and colleagues found that patient age, predisposition to heart disease, previous chest irradiation, and prior hormonal cancer therapy were associated with an individual’s risk of developing heart problems following epirubicin treatment. By contrast, the researchers found that treatment with less epirubicin, a higher tumor burden, prior chemotherapy, and older age of the patient were associated with an increased risk of death from other, non-cardiac, causes.

Based on these data, the researchers lowered the cumulative dose recommended for most patients, with maximum doses ranging from 300 mg/m2 to 900 mg/m2. "Treatment with a potentially cardiotoxic drug may often be inevitable to extend survival for a cancer patient. However, it is essential to be aware of the risk of cardiotoxicity, not only because cardiotoxicity can progress to a potentially fatal out¬come if not treated but also because it lowers the quality of patient life," the authors write.

In an accompanying editorial, Dawn Hershman, M.D., and Alfred I. Neugut, M.D., Ph.D., of Columbia University Medical Center in New York write that it has been difficult to predict which patients are most likely to develop cardiotoxicity following anthracycline therapy. Neither randomized clinical trials nor studies that rely on large administrative databases are adequate for addressing the issue. Therefore, Ryberg’s study is an important step to helping physicians personalize cancer care for their patients.

"If we can better predict who is at greatest risk for toxicity and who is not, we may be able to comfortably offer stan¬dard treatment to a larger percentage of the population," the editorialists write.

"Similar to a human skeleton, every cell has a cytoskeletal structure that supports the cell, gives it its shape, and provides a force that allows the cell to migrate. For the virus, this layer also presents a barrier," says  Yuntao Wu, assistant professor in George Mason University’s Department of Molecular and Microbiology. "We never understood how the virus overcomes this barrier to gain access to the center of the cell. Now we know that HIV triggers the mimicking of a cell process that activates cofilin, which cuts and modifies the cortical actin cytoskeleton and permits the virus to cross it."

Wu notes that the goal of his research was to attain a fundamental understanding of how the virus interacts with cells and the immune system in order to identify new ways to treat the disease. There is still much basic research left to be conducted before the findings from this study produce a clinical benefit. However, he believes that this discovery may later be used to develop a new treatment that could block viral interaction with, or viral alteration of, the cortical actin cytoskeleton.

Specifically, they show, binding of HIV to the receptor known as CXCR4 activates cofilin, a protein that disassembles actin microfilaments in the resting T cells. Those actin microfilaments are important building blocks of the cytoskeleton. That process is a required step for the virus to infect those resting cells, suggesting it may provide a useful new target for therapy, the researchers said.

" The ability of co-receptor engagement to alter intracellular biochemistry suggests that exposure of cells to HIV may in fact prime cells for HIV infection," said Wu and Jon Marsh of the National Institute of Mental Health. This first identification of the necessity of receptor signaling for infection also suggests "that HIV’s evolved selection of co-receptors is borne out of necessity."

In fact, the disassembly of actin microfilaments might actively assist HIV’s entry into the nucleus, Wu added. "When actin is cut, it grows back. That process may carry the virus from the cortical actin to inside the nucleus."

" It’s probably not just the breakdown of actin," Marsh agreed. Rather, he said, the rearrangement of actin may actively permit HIV’s transport to the nucleus. In support of that notion they found that complete actin breakdown hinders the virus’s ability to infect.

Earlier studies had shown that HIV relies on two CD4 coreceptors on the surface of T cells, CCR5 and CXCR4. CCR5 is expressed on activated, memory T cells where it plays a critical role in the susceptibility to HIV infection.

On the other hand, infection of resting T cells via CXCR4 seemed a more restricted process. Yet, in nearly one-half of the HIV-infected population, there is a conversion late in the disease to CXCR4 utilization, corresponding to an accelerated drop in T cell numbers, the researchers said.

Evidence had surfaced suggesting that the ability of HIV to establish itself in resting T cells, albeit slowly, is not purely passive, the researchers noted. Rather, studies had hinted that HIV may alter the cellular environment to facilitate infection and subsequent viral production. The new findings confirm that notion.

HIV’s newfound ability to rearrange the cytoskeleton of resting T cells with the help of cofilin may not be necessary in active memory T cells, Wu explained. That’s because cells that are actively cycling and migrating disassemble elements of the cytoskeleton themselves, leaving them naturally more susceptible to HIV’s entry.

" This is the first time we’ve been aware of cofilin’s activity in HIV infection of resting CD4 T cells," Wu said. Further study is required to identify exactly how the virus interacts to effect this change in cells and to further explore its potential as a target for treatment.

" This shows how much more we can learn," Marsh added. "HIV has evolved to utilize a great number of normal cellular processes. This is just another one."

The researchers include Alyson Yoder, George Mason University, Manassas, VA; Dongyang Yu, George Mason University, Manassas, VA; Li Dong, George Mason University, Manassas, VA Subashini R. Iyer, George Mason University, Manassas, VA Xuehua Xu, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD; Jeremy Kelly, George Mason University, Manassas, VA Juan Liu, George Mason University, Manassas, VA Weifeng Wang, George Mason University, Manassas, VA Paul J. Vorster, George Mason University, Manassas, VA Liane Agulto, George Mason University, Manassas, VA David A. Stephany, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD; James N. Cooper, George Mason University, Manassas, VA Jon W. Marsh, National Institute of Mental Health, Bethesda, MD; and Yuntao Wu, George Mason University, Manassas, VA, National Institute of Mental Health, Bethesda, MD.

Umbilical cord blood is rich in stem cells that can be used in a way similar to bone marrow to treat diseases such as childhood leukaemia. In future, it might also be used to repair damaged tissues in a range of diseases such as strokes, heart attacks, kidney failure, and diabetes.

Cord blood banks generally fall into two groups. Public banks collect cord blood which has been altruistically donated at birth and the blood is available to everyone. The value of public banks is now well established, but currently only a handful of UK hospitals collect cord blood for the public bank and coverage is insufficient to meet demand.

In contrast, commercial (private) banks offer parents the chance to store their child’s cord blood as biological insurance, in case it is needed to treat some future disease in the child or close family member. Customers typically pay £1500 for a 20-25 year service, but the chances of the blood being used are very small and these banks have been opposed by numerous medical bodies.

Private banks also raise serious resource issues for the NHS and are at risk of corporate failure.

Virgin recently introduced the concept of dual public-private banking. Virgin Health Bank stores 20% of the sample for private use and 80% for public use and uses some of the proceeds to support stem cell research.

In this way, Virgin has addressed the impasse between parents’ desire to store their baby’s cord blood and the unmet need for public banks, say the authors. Nevertheless, Virgin’s service still has many of the core disadvantages of private banking.

To succeed, Virgin will need to get the support of midwives and obstetricians who collect the blood and advise prospective customers, they write. The logistics of collection must also be streamlined to minimise burden on staff.

The charitable intent and public provision may help overturn entrenched professional opposition to commercial banking, say the authors, but fears about risks of private sector involvement in cord blood banking remain high.

These need allaying through greater transparency, strict regulation of financial practices, and greater accountability to public sector bodies through an appropriate regulatory framework, they conclude.

Many are also given cows’ milk, which has higher levels of salt than breast or formula milk, as their main drink despite recommendations that it should not be used in this way until babies are at least one year old. High levels of salt can damage developing kidneys, give children a taste for salty foods and establish poor eating practices that continue into adulthood and can result in health problems later in life.

These are the latest findings from researchers at the University of Bristol based on almost 1,200 participants in the Children of the 90s study and just published online by the European Journal of Clinical Nutrition.

The researchers found that the majority of infants were first introduced to solids around 3-4 months, with the mean salt intake for the highest group at 8 months more than double the maximum recommendation for that age group (400mg sodium per day up to 12 months). Infants in this top group often consumed cows’ milk as a main drink, which has a higher sodium content at 55mg per 100g than breast (15mg per 100g) or formula (15-30mg per 100ml) milk. They also ate three times the amount of bread compared to the lowest group, and were given salty flavourings such as yeast extract and gravy.

In the UK, the majority of salt consumed by individuals is added to food during manufacturing, with a relatively small proportion added during cooking or at the table and current intakes in both children and adults are far higher than NICE (National Institute for Health and Clinical Excellence) guidelines.

Speaking about the findings, Dr Pauline Emmett and Vicky Cribb, the nutritionists who conducted the research, said:

‘These findings show that salt intakes need to be substantially reduced in children of this age group. Infants need foods specifically prepared for them without added salt, so it is important to adapt the family diet.

‘This research suggests that clear advice is needed for parents about what foods are suitable for infants. This should be given to all parents and carers and should include the important advice not to use cows’ milk as a main drink before 12 months of age.’

They added that: ‘Given that three-quarters of salt in the diet comes from processed adult foods, successful salt-reduction strategies can only be achieved with the co-operation of the food industry. Manufacturers have a responsibility to reduce the salt content of food products. This process has already started in UK but much more needs to be done. If this study were repeated today it is likely that there would be some improvement but not enough to safeguard the health of all babies. ‘

The researchers studied three-day dietary records (completed by the mothers) of 1,178 8-month-old infants born in 1991/92 and involved in the Children of the 90s study at the University of Bristol. Infants were categorised into four groups of increasing salt intake.

Recent studies indicate that changes in diet may help prevent stroke, according to background information in the article. Hypertension, or high blood pressure, is a risk factor for stroke; therefore, dietary measures that reduce blood pressure may in turn affect stroke risk. Consuming more magnesium, calcium and potassium has been associated with lower blood pressure in previous studies, while sodium has been positively associated with hypertension.

Susanna C. Larsson, Ph.D., of the Karolinska Institutet, Stockholm, Sweden, and colleagues analyzed the diets of 26,556 Finnish male smokers age 50 to 69 years who had not previously had strokes. In addition to the types of food they ate, the men reported other characteristics including medical, smoking and physical activity histories. Their height, weight and blood pressure were recorded, and a blood sample was taken.

During an average of 13.6 years of follow-up, 2,702 of the men had cerebral infarctions; 383 had intracerebral hemorrhages, which involve bleeding into the brain tissue; 196 had subarachnoid hemorrhages, or bleeding between the brain and the thin tissues that cover it; and 84 had unspecified types of strokes.

After adjusting for age and cardiovascular risk factors, such as diabetes and cholesterol level, men who consumed the most magnesium (an average of 589 milligrams per day) had a 15 percent lower risk for cerebral infarction than those who consumed the least (an average of 373 milligrams per day). The association was stronger in men younger than 60 years. Magnesium intake was not associated with a lower risk of intracerebral or subarachnoid hemorrhage, and calcium, potassium and sodium intake were not associated with risk for any type of stroke.

"An inverse association between magnesium intake and cerebral infarction is biologically plausible," the authors write. In addition to lowering blood pressure, magnesium may influence cholesterol concentrations or the body’s use of insulin to turn glucose into energy. Either of these mechanisms would affect the risk for cerebral infarction but not hemorrhage.

The results "suggest that a high consumption of magnesium-rich foods, such as whole-grain cereals, may play a role in the prevention of cerebral infarction," they write. "Whether magnesium supplementation lowers the risk of cerebral infarction needs to be assessed in large, long-term randomized trials."

Journal reference: Arch Intern Med. 2008;168[5]:459-465.

The ATBC Study was supported by Public Health Service contracts from the National Cancer Institute. Dr. Larsson’s postdoctoral research at the National Public Health Institute was supported by a grant from the Swedish Council for Working Life and Social Research.

The study, published in the Dec. 13 Nature, was led by Katherine Whitcome, a postdoctoral researcher in the Department of Anthropology in Harvard’s Faculty of Arts and Sciences, with Daniel Lieberman, professor of anthropology at Harvard, and Liza Shapiro, associate professor of anthropology of the University of Texas at Austin.

"Pregnancy presents an enormous challenge for the female body," says Whitcome. "The body must change in dramatic ways to accommodate the baby, and these changes affect a woman’s stability and posture. It turns out that enhanced curvature and reinforcement of the lower spine are key to maintaining normal activities during pregnancy."

It has long been appreciated that giving birth to large-brained infants has influenced human pelvic shape, but there has been little attention paid to the major challenge that pregnant bipedal mothers endure when holding up an enormous fetus and placenta well in front of the hip joints. The study is the first of its kind to examine the evolutionary mechanisms that allow women to carry a baby to term, and the way that women’s bodies compensate for increased weight in the abdomen during pregnancy.

Walking on two feet, which happened early in human evolution, presents a unique challenge during pregnancy because the center of gravity shifts far in front of the hips, destabilizing the upper body and impairing locomotion. This is not the case for animals that walk predominantly on four legs such as chimpanzees, or even other bipeds.

To accommodate this shifted center of gravity, women’s spines have evolved to help offset the additional weight in the abdomen during pregnancy, so that the back muscles are not taxed in counter-balancing the destabilizing effects of the baby’s weight.

In both women and men the curvature of the spine in the lower back, called the lordosis, stabilizes the upper body above the lower body. The researchers studied 19 pregnant women between the ages of 20 and 40, and found that when naturally standing, the women lean back, increasing their lordosis by as much as 60 percent by the end of their term. In doing so, pregnant women maintain a stable center of gravity above the hips.

The research also demonstrates, for the first time, that human lumbar vertebrae differ between males and females in ways that decrease the shearing forces that the lumbar extension of pregnancy places on the lower back in pregnant mothers.

"In females, the lordosis is subtly different than that of males, because the curvature extends across three vertebrae, while the male lordosis curves across only two vertebrae," says Whitcome. "Loading across three vertebrae allows an expectant mother to increase her lordosis, realigning her center of gravity above her hips and offsetting the destabilizing weight of the baby."

In addition to the difference in the number of vertebrae across which the lordosis spans, the female joints are relatively larger and flare out further down the spine than those of males improving the spine’s strength. All of this contributes to an increased ability to extend the spine, so that the woman can lean back, realign the body’s center of gravity, and safely maintain a more stable position. These differences in the lower back may even reinforce her capability to support and carry her baby in her arms after the baby has been born.

When human ancestors first became bipedal, they set the human lineage off on a different evolutionary path from other apes, but in so doing created special challenges for pregnant mothers. One exciting discovery is that the ability of human females to better carry a baby to term while standing on two feet appears to have evolved at least two million years ago. The researchers studied two hominin fossils that were approximately two million years old, one of which – presumably a female – displayed three lordosis vertebrae and one of which – presumably a male – displayed fewer.

"Early human women lived very strenuous, active lives, and pregnant females were forced to cope with the discomfort of childbearing while foraging for food and escaping from predators," Lieberman says. "This evolution of the lower back helped early woman to remain more mobile during pregnancy, which would have been essential to survival, and appears to have been favored by natural selection."

The research was funded by the National Science Foundation, the L.S.B. Leakey Foundation, and the American School of Prehistoric Research.

Researchers from Oregon State University and the University of Florida have identified how those factors mesh to create heightened risk of the West Nile Virus in southern Florida, and they hope to expand their studies to the rest of the nation.

Results of the research have been published by the Centers for Disease Control.

Many early hydrologic models predicting the transmission of West Nile Virus and other mosquito-borne diseases may have been a bit too simplistic, relying on factors such as total rainfall to estimate disease risk, said Jeffrey Shaman, an assistant professor of atmospheric sciences at Oregon State University. The situation, he adds, is much more complex.

"In some cases, rain can actually help control mosquitoes by flushing away larval habitats," Shaman said. "And simply having more mosquitoes doesn’t necessarily mean that we’ll experience a greater incidence of West Nile Virus. The mosquitoes themselves must first be infected with the virus. Researchers call the process through which more mosquitoes become infected ‘amplification,’ and there are a number of factors that lead to that stage.

"By identifying these factors in the wild, it will enhance our ability to create control strategies."

In their studies, Shaman and colleague Jonathan F. Day from the University of Florida found that spring drought followed by continual summer rainfall is critical for the amplification and transmission of West Nile Virus and a similar disease, St. Louis Encephalitis Virus, in southern Florida. When drought occurs early in the year, the limited water resources confine mosquito populations to selected habitats — specifically isolated, densely vegetated hammocks where conditions remain humid.

These moist hammocks also happen to be the spring nesting and roosting sites of many species of wild birds, which act as hosts and carriers for the diseases. While confined in the hammocks, the mosquitoes feed almost exclusively on the nesting birds and as a result, each bird is bitten by numerous mosquitoes. A single infected bird can thus infect many more mosquitoes than if conditions were wet and the mosquitoes were more broadly dispersed, Shaman said.

"This phenomenon, called ‘drought-induced amplification,’ is a key to transmission," he said.

When summer rainfall increases, surface humidity levels rise and the mosquitoes are able to disperse and initiate secondary transmission away from the original amplification sites, the researchers pointed out. With this dispersal, the mosquitoes are more likely to come into contact with humans — elevating the risk of human incidence of the diseases.

"Drought-induced amplification may be somewhat unique to southern Florida, where drought tends to occur in the spring and coincides with the birds’ nesting season," Shaman said. "The mosquito situation itself also is somewhat unusual. In most areas of the country, one species of mosquito infects the birds and another species then passes the disease along to humans.

"Florida has one species of mosquito that routinely bites both," he added.

Not all of the world’s more than 3,600 species of mosquitoes transmit diseases to humans. The mosquito must be sufficiently competent to act as a carrier, thus some species can act as hosts for certain diseases, while others are more "refractive," — not carrying enough of the disease to transmit it.

West Nile Virus transmission requires mosquito species that prefer feeding on birds, but like mosquitoes, not all birds are good carriers. Some are ineffective hosts, Shaman said, while others — like crows — are very susceptible and may die from the virus. Birds that are effective hosts may carry the virus and infect biting mosquitoes for 4-5 days before recovering from the illness.

"It is this coming together of factors that leads to the spread of the disease," Shaman said. "But because the amplification is concentrated — in time and space — it does make it easier to devise control strategies. Chemical application is the most likely scenario, but because it could be applied in selected areas, it would be more cost-effective and potentially less environmentally threatening."

The spread of West Nile Virus through the U.S. has been sporadic, the researchers say, with hotspots arising one year in Colorado, and other regions during other years. The key to understanding the spread of the disease is to investigate the local conditions that may lead to amplification.

"It is a localized phenomenon," Shaman said. "We have to understand what goes on at the local level, at the appropriate scale, before we can reach the same conclusions that we found in southern Florida. But in almost all cases, the amplification of West Nile Virus will start with mosquitoes that carry the disease mingling with birds that are good carriers.

"How fast and far it spreads from there depends on weather, terrain, vegetation, humidity, the types of birds that live in the region and even the number of housing developments in a given area," he added. "These are the variables that need to be studied across the country."

Shaman and Day hope to expand their studies to analyze different regions of the country and create models similar to that of southern Florida, where certain weather patterns set off the chain of events that leads to amplification.