When scientists try to predict the spread of something across populations -- anything from a coronavirus to misinformation -- they use complex mathematical models to do so. Typically, they'll study the first few steps in which the subject spreads, and use that rate to project how far and wide the spread will go.
But what happens if a pathogen mutates, or information becomes modified, changing the speed at which it spreads? In a new study appearing in this week's issue of Proceedings of the National Academy of Sciences (PNAS), a team of Carnegie Mellon University researchers show for the first time how important these considerations are.
"These evolutionary changes have a huge impact," says CyLab faculty member Osman Yagan, an associate research professor in Electrical and Computer Engineering (ECE) and corresponding author of the study. "If you don't consider the potential changes over time, you will be wrong in predicting the number of people that will get sick or the number of people who are exposed to a piece of information."
Most people are familiar with epidemics of disease, but information itself -- nowadays traveling at lightning speeds over social media -- can experience its own kind of epidemic and "go viral." Whether a piece of information goes viral or not can depend on how the original message is tweaked.
"Some pieces of misinformation are intentional, but some may develop organically when many people sequentially make small changes like a game of 'telephone,'" says Yagan. "A seemingly boring piece of information can evolve into a viral Tweet, and we need to be able to predict how these things spread."
In their study, the researchers developed a mathematical theory that takes these evolutionary changes into consideration. They then tested their theory against thousands of computer-simulated epidemics in real-world networks, such as Twitter for the spread of information or a hospital for the spread of disease.
In the context of spreading of infectious disease, the team ran thousands of simulations using data from two real-world networks: a contact network among students, teachers, and staff at a US high school, and a contact network among staff and patients in a hospital in Lyon, France.
These simulations served as a test bed: the theory that matches what is observed in the simulations would prove to be the more accurate one.
"We showed that our theory works over real-world networks," says the study's first author, Rashad Eletreby, who was a Carnegie Mellon Ph.D. student when he wrote the paper. "Traditional models that don't consider evolutionary adaptations fail at predicting the probability of the emergence of an epidemic."
While the study isn't a silver bullet for predicting the spread of today's coronavirus or the spread of fake news in today's volatile political environment with 100% accuracy -- one would need real-time data tracking the evolution of the pathogen or information to do that -- the authors say it's a big step.
Read more at Science Daily
Showing posts with label Epedemic. Show all posts
Showing posts with label Epedemic. Show all posts
Mar 1, 2020
Lessons learned from addressing myths about Zika and yellow fever outbreaks in Brazil
When disease epidemics and outbreaks occur, conspiracy theories often emerge that compete with the information provided by public health officials. A Dartmouth-led study in Science Advances finds that information used to counter myths about Zika in Brazil not only failed to reduce misperceptions but also reduced the accuracy of people's other beliefs about the disease.
The results provide important context as countries launch public information campaigns about the new coronavirus (COVID-19), including how to protect oneself and prevent the spread of the disease.
"It is essential to evaluate public health messaging and information campaigns," said co-author Brendan Nyhan, a professor of government at Dartmouth. "Our results indicate that efforts to correct misperceptions about emerging diseases like Zika may not be as effective as we might hope."
The study was based on a nationally representative survey conducted in Brazil in 2017 and online survey experiments conducted there in 2017 (not long after the 2015-2016 Zika epidemic) and in 2018 (just after an unusually severe yellow fever outbreak). Using survey data, the team first demonstrated the prevalence of misperceptions among Brazilians about whether Zika can be transmitted through sexual contact (true) or casual contact (false).
The researchers then conducted three preregistered experiments testing the effectiveness of information provided by public health officials to dispel myths about Zika and yellow fever. These studies, which were conducted online among Brazilian adults, showed that corrective information about Zika not only failed to reduce misperceptions but also frequently reduced the accuracy of other beliefs people held about the disease (a finding that was replicated in both the 2017 and 2018 data).
The researchers found that corrective information about yellow fever was more effective than the material about Zika. However, exposure to this information did not increase support for public policies aimed at preventing the spread of either disease nor did it change people's intentions to engage in preventive behaviors.
From Science Daily
The results provide important context as countries launch public information campaigns about the new coronavirus (COVID-19), including how to protect oneself and prevent the spread of the disease.
"It is essential to evaluate public health messaging and information campaigns," said co-author Brendan Nyhan, a professor of government at Dartmouth. "Our results indicate that efforts to correct misperceptions about emerging diseases like Zika may not be as effective as we might hope."
The study was based on a nationally representative survey conducted in Brazil in 2017 and online survey experiments conducted there in 2017 (not long after the 2015-2016 Zika epidemic) and in 2018 (just after an unusually severe yellow fever outbreak). Using survey data, the team first demonstrated the prevalence of misperceptions among Brazilians about whether Zika can be transmitted through sexual contact (true) or casual contact (false).
The researchers then conducted three preregistered experiments testing the effectiveness of information provided by public health officials to dispel myths about Zika and yellow fever. These studies, which were conducted online among Brazilian adults, showed that corrective information about Zika not only failed to reduce misperceptions but also frequently reduced the accuracy of other beliefs people held about the disease (a finding that was replicated in both the 2017 and 2018 data).
The researchers found that corrective information about yellow fever was more effective than the material about Zika. However, exposure to this information did not increase support for public policies aimed at preventing the spread of either disease nor did it change people's intentions to engage in preventive behaviors.
From Science Daily
Feb 11, 2020
To slow an epidemic, focus on handwashing
A new study estimates that improving the rates of handwashing by travelers passing through just 10 of the world's leading airports could significantly reduce the spread of many infectious diseases. And the greater the improvement in people's handwashing habits at airports, the more dramatic the effect on slowing the disease, the researchers found.
The findings, which deal with infectious diseases in general including the flu, were published in late December, just before the recent coronavirus outbreak in Wuhan, China, but the study's authors say that its results would apply to any such disease and are relevant to the current outbreak.
The study, which is based on epidemiological modeling and data-based simulations, appears in the journal Risk Analysis. The authors are Professor Christos Nicolaides PhD '14 of the University of Cyprus, who is also a fellow at the MIT Sloan School of Management; Professor Ruben Juanes of MIT's Department of Civil and Environmental Engineering; and three others.
People can be surprisingly casual about washing their hands, even in crowded locations like airports where people from many different locations are touching surfaces such as chair armrests, check-in kiosks, security checkpoint trays, and restroom doorknobs and faucets. Based on data from previous research by groups including the American Society for Microbiology, the team estimates that on average, only about 20 percent of people in airports have clean hands -- meaning that they have been washed with soap and water, for at least 15 seconds, within the last hour or so. The other 80 percent are potentially contaminating everything they touch with whatever germs they may be carrying, Nicolaides says.
"Seventy percent of the people who go to the toilet wash their hands afterwards," Nicolaides says, about findings from a previous ASM study. "The other 30 percent don't. And of those that do, only 50 percent do it right." Others just rinse briefly in some water, rather than using soap and water and spending the recommended 15 to 20 seconds washing, he says. That figure, combined with estimates of exposure to the many potentially contaminated surfaces that people come into contact with in an airport, leads to the team's estimate that about 20 percent of travelers in an airport have clean hands.
Improving handwashing at all of the world's airports to triple that rate, so that 60 percent of travelers to have clean hands at any given time, would have the greatest impact, potentially slowing global disease spread by almost 70 percent, the researchers found. Deploying such measures at so many airports and reaching such a high level of compliance may be impractical, but the new study suggests that a significant reduction in disease spread could still be achieved by just picking the 10 most significant airports based on the initial location of a viral outbreak. Focusing handwashing messaging in those 10 airports could potentially slow the disease spread by as much as 37 percent, the researchers estimate.
They arrived at these estimates using detailed epidemiological simulations that involved data on worldwide flights including duration, distance, and interconnections; estimates of wait times at airports; and studies on typical rates of interactions of people with various elements of their surroundings and with other people.
Even small improvements in hygiene could make a noticeable dent. Increasing the prevalence of clean hands in all airports worldwide by just 10 percent, which the researchers think could potentially be accomplished through education, posters, public announcements, and perhaps improved access to handwashing facilities, could slow the global rate of the spread of a disease by about 24 percent, they found. Numerous studies (such as this one) have shown that such measures can increase rates of proper handwashing, Nicolaides says.
"Eliciting an increase in hand-hygiene is a challenge," he says, "but new approaches in education, awareness, and social-media nudges have proven to be effective in hand-washing engagement."
The researchers used data from previous studies on the effectiveness of handwashing in controlling transmission of disease, so Juanes says these data would have to be calibrated in the field to obtain refined estimates of the slow-down in spreading of a specific outbreak.
The findings are consistent with recommendations made by both the U.S. Centers for Disease Control and the World Health Organization. Both have indicated that hand hygiene is the most efficient and cost-effective way to control disease propagation. While both organizations say that other measures can also play a useful role in limiting disease spread, such as use of surgical face masks, airport closures, and travel restrictions, hand hygiene is still the first line of defense -- and an easy one for individuals to implement.
While the potential of better hand hygiene in controlling transmission of diseases between individuals has been extensively studied and proven, this study is one of the first to quantitatively assess the effectiveness of such measures as a way to mitigate the risk of a global epidemic or pandemic, the authors say.
The researchers identified 120 airports that are the most influential in spreading disease, and found that these are not necessarily the ones with the most overall traffic. For example, they cite the airports in Tokyo and Honolulu as having an outsized influence because of their locations. While they respectively rank 46th and 117th in terms of overall traffic, they can contribute significantly to the spread of disease because they have direct connections to some of the world's biggest airport hubs, they have long-range direct international flights, and they sit squarely between the global East and West.
For any given disease outbreak, identifying the 10 airports from this list that are the closest to the location of the outbreak, and focusing handwashing education at those 10 turned out to be the most effective way of limiting the disease spread, they found.
Read more at Science Daily
The findings, which deal with infectious diseases in general including the flu, were published in late December, just before the recent coronavirus outbreak in Wuhan, China, but the study's authors say that its results would apply to any such disease and are relevant to the current outbreak.
The study, which is based on epidemiological modeling and data-based simulations, appears in the journal Risk Analysis. The authors are Professor Christos Nicolaides PhD '14 of the University of Cyprus, who is also a fellow at the MIT Sloan School of Management; Professor Ruben Juanes of MIT's Department of Civil and Environmental Engineering; and three others.
People can be surprisingly casual about washing their hands, even in crowded locations like airports where people from many different locations are touching surfaces such as chair armrests, check-in kiosks, security checkpoint trays, and restroom doorknobs and faucets. Based on data from previous research by groups including the American Society for Microbiology, the team estimates that on average, only about 20 percent of people in airports have clean hands -- meaning that they have been washed with soap and water, for at least 15 seconds, within the last hour or so. The other 80 percent are potentially contaminating everything they touch with whatever germs they may be carrying, Nicolaides says.
"Seventy percent of the people who go to the toilet wash their hands afterwards," Nicolaides says, about findings from a previous ASM study. "The other 30 percent don't. And of those that do, only 50 percent do it right." Others just rinse briefly in some water, rather than using soap and water and spending the recommended 15 to 20 seconds washing, he says. That figure, combined with estimates of exposure to the many potentially contaminated surfaces that people come into contact with in an airport, leads to the team's estimate that about 20 percent of travelers in an airport have clean hands.
Improving handwashing at all of the world's airports to triple that rate, so that 60 percent of travelers to have clean hands at any given time, would have the greatest impact, potentially slowing global disease spread by almost 70 percent, the researchers found. Deploying such measures at so many airports and reaching such a high level of compliance may be impractical, but the new study suggests that a significant reduction in disease spread could still be achieved by just picking the 10 most significant airports based on the initial location of a viral outbreak. Focusing handwashing messaging in those 10 airports could potentially slow the disease spread by as much as 37 percent, the researchers estimate.
They arrived at these estimates using detailed epidemiological simulations that involved data on worldwide flights including duration, distance, and interconnections; estimates of wait times at airports; and studies on typical rates of interactions of people with various elements of their surroundings and with other people.
Even small improvements in hygiene could make a noticeable dent. Increasing the prevalence of clean hands in all airports worldwide by just 10 percent, which the researchers think could potentially be accomplished through education, posters, public announcements, and perhaps improved access to handwashing facilities, could slow the global rate of the spread of a disease by about 24 percent, they found. Numerous studies (such as this one) have shown that such measures can increase rates of proper handwashing, Nicolaides says.
"Eliciting an increase in hand-hygiene is a challenge," he says, "but new approaches in education, awareness, and social-media nudges have proven to be effective in hand-washing engagement."
The researchers used data from previous studies on the effectiveness of handwashing in controlling transmission of disease, so Juanes says these data would have to be calibrated in the field to obtain refined estimates of the slow-down in spreading of a specific outbreak.
The findings are consistent with recommendations made by both the U.S. Centers for Disease Control and the World Health Organization. Both have indicated that hand hygiene is the most efficient and cost-effective way to control disease propagation. While both organizations say that other measures can also play a useful role in limiting disease spread, such as use of surgical face masks, airport closures, and travel restrictions, hand hygiene is still the first line of defense -- and an easy one for individuals to implement.
While the potential of better hand hygiene in controlling transmission of diseases between individuals has been extensively studied and proven, this study is one of the first to quantitatively assess the effectiveness of such measures as a way to mitigate the risk of a global epidemic or pandemic, the authors say.
The researchers identified 120 airports that are the most influential in spreading disease, and found that these are not necessarily the ones with the most overall traffic. For example, they cite the airports in Tokyo and Honolulu as having an outsized influence because of their locations. While they respectively rank 46th and 117th in terms of overall traffic, they can contribute significantly to the spread of disease because they have direct connections to some of the world's biggest airport hubs, they have long-range direct international flights, and they sit squarely between the global East and West.
For any given disease outbreak, identifying the 10 airports from this list that are the closest to the location of the outbreak, and focusing handwashing education at those 10 turned out to be the most effective way of limiting the disease spread, they found.
Read more at Science Daily
Feb 1, 2020
Modeling study estimates spread of 2019 novel coronavirus
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| Coronavirus diagnosis concept |
Senior author Professor Gabriel Leung from the University of Hong Kong highlights: "Not everyone who is infected with 2019-nCoV would require or seek medical attention. During the urgent demands of a rapidly expanding epidemic of a completely new virus, especially when system capacity is getting overwhelmed, some of those infected may be undercounted in the official register."
He explains: "The apparent discrepancy between our modelled estimates of 2019-nCoV infections and the actual number of confirmed cases in Wuhan could also be due to several other factors. These include that there is a time lag between infection and symptom onset, delays in infected persons coming to medical attention, and time taken to confirm cases by laboratory testing, which could all affect overall recording and reporting."
The new estimates also suggest that multiple major Chinese cities might have already imported dozens of cases of 2019-nCoV infection from Wuhan, in numbers sufficient to initiate local epidemics.
The early estimates underscore that it will likely take rapid and immediate scale-up of substantial public health control measures to prevent large epidemics in areas outside Wuhan. Further analyses suggest that if transmissibility of 2019-nCoV could be reduced, both the growth rate and size of local epidemics in all cities across China could be reduced.
"If the transmissibility of 2019-nCoV is similar nationally and over time, it is possible that epidemics could be already growing in multiple major Chinese cities, with a time lag of one to two weeks behind the Wuhan outbreak," says lead author Professor Joseph Wu from the University of Hong Kong. "Large cities overseas with close transport links to China could potentially also become outbreak epicentres because of substantial spread of pre-symptomatic cases unless substantial public health interventions at both the population and personal levels are implemented immediately."
According to Professor Gabriel Leung: "Based on our estimates, we would strongly urge authorities worldwide that preparedness plans and mitigation interventions should be readied for quick deployment, including securing supplies of test reagents, drugs, personal protective equipment, hospital supplies, and above all human resources, especially in cities with close ties with Wuhan and other major Chinese cities."
In the study, researchers used mathematical modelling to estimate the size of the epidemic based on officially reported 2019-nCoV case data and domestic and international travel (i.e., train, air, road) data. They assumed that the serial interval estimate (the time it takes for infected individuals to infect other people) for 2019-nCoV was the same as for severe acute respiratory syndrome (SARS: table 1). The researchers also modelled potential future spread of 2019-nCoV in China and internationally, accounting for the potential impact of various public health interventions that were implemented in January 2020 including use of face masks and increased personal hygiene, and the quarantine measures introduced in Wuhan on January 23.
The researchers estimate that in the early stages of the Wuhan outbreak (from December 1, 2019 to January 25, 2020) each person infected with 2019-nCoV could have infected up to 2-3 other individuals on average, and that the epidemic doubled in size every 6.4 days. During this period, up to 75,815 individuals could have been infected in Wuhan.
Additionally, estimates suggest that cases of 2019-nCoV infection may have spread from Wuhan to multiple other major Chinese cities as of January 25, including Guangzhou (111 cases), Beijing (113), Shanghai (98), and Shenzhen (80; figure 3). Together these cities account for over half of all outbound international air travel from China.
While the estimates suggest that the quarantine in Wuhan may not have the intended effect of completely halting the epidemic, further analyses suggest that if transmissibility of 2019-nCoV could be reduced by 25% in all cities nationally with expanded control efforts, both the growth rate and size of local epidemics could be substantially reduced. Moreover, a 50% reduction in transmissibility could shift the current 2019-nCoV epidemic from one that is expanding rapidly, to one that is slowly growing (figure 4).
"It might be possible to reduce local transmissibility and contain local epidemics if substantial, even draconian, measures that limit population mobility in all affected areas are immediately considered. Precisely what and how much should be done is highly contextually specific and there is no one-size-fits-all set of prescriptive interventions that would be appropriate across all settings," says co-author Dr Kathy Leung from the University of Hong Kong. "On top of that, strategies to drastically reduce within-population contact by cancelling mass gatherings, school closures, and introducing work-from-home arrangements could contain the spread of infection so that the first imported cases, or even early local transmission, does not result in large epidemics outside Wuhan."
Read more at Science Daily
Jan 16, 2018
Possible cause of early colonial-era Mexican epidemic identified
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| Excavated structure at the northern edge of the Grand Plaza at Teposcolula-Yucundaa. Architectural investigations of the Grand Plaza resulted in the unexpected discovery of a large epidemic cemetery associated with the 1545-1550 cocoliztli epidemic. The cemetery was found to contain numerous mass burials, attesting to the catastrophic nature of the epidemic. |
After European contact, dozens of epidemics swept through the Americas, devastating New World populations. Although many first-hand accounts of these epidemics were recorded, in most cases it has been difficult, if not impossible, for researchers to definitively identify their causes based on historical descriptions of their symptoms alone. In some cases, for example, the symptoms caused by infection of different bacteria or viruses might be very similar, or the symptoms presented by certain diseases may have changed over the past 500 years. Consequently, researchers have hoped that advancements in ancient DNA analysis and other such approaches might provide a breakthrough in identifying the unknown causes of past epidemics.
The first direct evidence for one of the potential causes of the 1545-1550 cocoliztli epidemic
Of all the colonial New World epidemics, the unidentified 1545-1550 "cocoliztli" epidemic was among the most devastating, affecting large parts of Mexico and Guatemala, including the Mixtec town of Teposcolula-Yucundaa, located in Oaxaca, Mexico. Archaeological excavations at the site have unearthed the only known cemetery linked to this particular outbreak to date. "Given the historical and archaeological context of Teposcolula-Yucundaa, it provided us with a unique opportunity to address the question regarding the unknown microbial causes responsible for this epidemic," explains Åshild J. Vågene of the MPI-SHH, co-first author of the study. After the epidemic, the city of Teposcolula-Yucundaa was relocated from the top of a mountain to the neighboring valley, leaving the epidemic cemetery essentially untouched prior to recent archaeological excavations. These circumstances made Teposcolula-Yucundaa an ideal site to test a new method to search for direct evidence of the cause of the disease.
The scientists analyzed ancient DNA extracted from 29 skeletons excavated at the site, and used a new computational program to characterize the ancient bacterial DNA. This technique allowed the scientists to search for all bacterial DNA present in their samples, without having to specify a particular target beforehand. This screening method revealed promising evidence of S. enterica DNA traces in 10 of their samples. Subsequent to this initial finding, a DNA enrichment method specifically designed for this study was applied. With this, the scientists were able to reconstruct full S. enterica genomes, and 10 of the individuals were found to contain a subspecies of S. enterica that causes enteric fever. This is the first time scientists have recovered molecular evidence of a microbial infection from this bacterium using ancient material from the New World. Enteric fever, of which typhoid fever is the best known variety today, causes high fevers, dehydration, and gastro-intestinal complications. Today, the disease is considered a major health threat around the world, having caused an estimated 27 million illnesses in the year 2000 alone. However, little is known about its past severity or worldwide prevalence.
A new tool in discovering past diseases
"A key result of this study is that we were successful in recovering information about a microbial infection that was circulating in this population, and we did not need to specify a particular target in advance," explains Alexander Herbig, also of the MPI-SHH and co-first author of the study. In the past, scientists usually targeted a particular pathogen or a small set of pathogens, for which they had prior indication.
Read more at Science Daily
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