Archive for the ‘epidemiology’ Category

US states stopped their pandemic social restrictions too soon

October 8th, 2020
A masked man and woman walks outside a plastic barrier.

Enlarge / If you can't socially distance, a face mask helps. (credit: Christopher Furlong / Getty Images)

Many countries that controlled their COVID-19 cases in the spring are now seeing rises in infections, raising the prospect that they'll face a second wave of cases, as many epidemiological models had predicted. But in the United States, the number of cases has never dropped to low levels. Instead, it varied between high levels of infection and very high peaks in cases. Why is everything so different in the states?

While there are plenty of possible reasons, a series of new studies essentially blame all the obvious ones: the United States ended social distancing rules too soon, never built up sufficient testing and contact-tracing capabilities, and hasn't adopted habits like mask use that might help substitute for its failures elsewhere. The fact that some of these studies used very different methods to arrive at similar conclusions suggests that those conclusions are likely to hold up as more studies come in.

Too soon

One of the studies, performed by a US-South African team, looked at the relaxation of social distancing rules in the US. Its authors created a list of restrictions for each state and the District of Columbia and tracked the number of COVID-19 deaths in each state for eight weeks prior to the rules being terminated. The number of deaths was used as a proxy for the total number of cases, as the erratic availability of tests made the true infection rate difficult to determine.

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Posted in Biology, COVID-19, epidemiology, medicine, pandemic, public health, SARS-CoV-2, science | Comments (0)

How the Warsaw Ghetto beat back typhus during World War II

September 13th, 2020
Painting by Israel Bernbaum depicting Jewish children in Warsaw Ghetto and in the death camps (1981).

Enlarge / Painting by Israel Bernbaum depicting Jewish children in Warsaw Ghetto and in the death camps (1981). (credit: Monclair State University collection)

During the Nazi occupation of Poland during World War II, Jewish residents in Warsaw were forcibly confined to a district known as the Warsaw Ghetto. The crowded, unsanitary conditions and meager food rations predictably led to a deadly outbreak of typhus fever in 1941. But the outbreak mysteriously halted before winter arrived, rather than becoming more virulent with the colder weather. According to a recent paper in the journal Science Advances, it was measures put into place by the ghetto doctors and Jewish council members that curbed the spread of typhus: specifically, social distancing, self-isolation, public lectures, and the establishment of an underground university to train medical students.

Typhus (aka "jail fever" or "gaol fever") has been around for centuries. These days, outbreaks are relatively rare, limited to regions with bad sanitary conditions and densely packed populations—prisons and ghettos, for instance—since the epidemic variety is spread by body lice. (Technically, typhus is a group of related infectious diseases.) But they do occur: there was an outbreak among the Los Angeles homeless population in 2018-2019.

Those who contract typhus experience a sudden fever and accompanying flu-like symptoms, followed five to nine days later by a rash that gradually spreads over the body. If left untreated with antibiotics, the patient begins to show signs of meningoencephalitis (infection of the brain)—sensitivity to light, seizures, and delirium, for instance—before slipping into a coma and, often, dying. There is no vaccine against typhus, even today. It's usually prevented by limiting human exposure to the disease vectors (lice) by improving the conditions in which outbreaks can flourish.

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Posted in bacteriology, epidemiology, Gaming & Culture, History, infectious diseases, mathematics, science, statistics, typhus, Warsaw Ghetto, World War II | Comments (0)

How does a Sturgis-sized crowd affect COVID-19? It’s complicated

September 12th, 2020
STURGIS, SD—People walk along Main Street during the 80th Annual Sturgis Motorcycle Rally in Sturgis, South Dakota on August 8, 2020.

Enlarge / STURGIS, SD—People walk along Main Street during the 80th Annual Sturgis Motorcycle Rally in Sturgis, South Dakota on August 8, 2020. (credit: Michael Ciaglo | Getty Images)

The coronavirus loves a crowd. Put enough warm, susceptible bodies together and it's sure to spread. Scientists have known that since nearly the start of the pandemic, from studying Covid-19 outbreaks aboard the Diamond Princess cruise ship, inside a megachurchin South Korea, at a Champions League soccer match in Italy. Countless other clusters have since been recorded, often seeded by a single contagious individual.

It’s the danger of crowds that led the governments of other countries to enact national lockdowns. In the United States, it was more of a patchwork of state and local stay-at-home orders, school closures, and bans on mass gatherings. As scientists have learned more about the specific conditions that can lead to such superspreading events—unmasked people talking, singing, or exercising inside poorly ventilated indoor spaces—that’s made it possible, in theory, to fine-tune these disease containment strategies, and to ease up on the most dramatic restrictions and focus on the policies that do the most to stem the spread of the virus.

But people also love a crowd. And over the late spring and summer, a number of mass gatherings—often anxiously watched by the media, health care professionals, and worried neighbors—became real-life experiments in what happens when you put people together in the Covid-19 era. The events ranged from the apolitical (spring break, summer camp, back-to-school) to the politically supercharged (President Trump’s Tulsa rally, “reopen” protests, anti-police brutality protests, and ongoing demonstrations in Portland against the use of federal agents). Each one tested different variables—masks versus no masks, indoors versus outdoors—but all elicited an opportunity to study the same questions: How many people would get sick as a result, how many would die, and who would bear the cost of the health care bill?

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Posted in COVID-19, covid19, epidemiology, science, Sturgis | Comments (0)

New study models ways of emerging from a pandemic lockdown

August 7th, 2020
Testing and contact tracing may be essential for exiting pandemic lockdowns.

Enlarge / Testing and contact tracing may be essential for exiting pandemic lockdowns. (credit: Sean Gallup / Getty Images)

As the scale and threat of the COVID-19 pandemic became clear, researchers who trace the spread of diseases were pretty unanimous: to buy us time to develop a therapy or vaccine, countries needed to implement heavy-handed restrictions to limit the opportunities for the virus to spread. Experts painted frightening pictures of huge peaks of infections that would overwhelm local hospital systems if lockdowns weren't put in place, leading to many unnecessary deaths. For countries like Italy and Spain, which were already in the throes of an uncontrolled spread, reality bore these predictions out. Peaks rose sharply in advance of restrictions but fell nearly as sharply once they were put in place.

But those same models also predicted that ending the restrictions would put countries at risk of a return of the virus a few months later, forcing governments to again decide between strict restrictions or an out-of-control pandemic in the next step of a cycle that would repeat until a vaccine or therapy became available. Those countries now have a somewhat different question: are there ways of controlling the virus without resorting to a cycle of on-and-off lockdowns? For countries like the US, which implemented restrictions briefly, erratically, and half heartedly, such that peaks haven't been separated by much of a trough, the same question will become relevant if we ever get the virus under control.

A new study by a large international team uses epidemiological models to explore ways of keeping things in check while allowing most of the population to resume a semi-normal life. It finds that there are ways of handling restriction easing, but they require a combination of an effective contact tracing system, extensive testing, and a willingness of households to quarantine together.

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Posted in Biology, contact tracing, COVID-19, epidemiology, lockdowns, medicine, pandemic, SARS-CoV-2, science | Comments (0)

Slow relaxation of COVID-19 rules helps push recurrence back

June 24th, 2020
Masked chefs work in a professional kitchen.

Enlarge / Spanish chef Jordi Roca prepares dishes at the "El Celler de Can Roca" restaurant in Girona on June 23, 2020, on the day it reopens after a national lockdown to stop the spread of the novel coronavirus. (credit: JOSEP LAGO / Getty Images)

Countries like the United States have never really gotten the pandemic under control, while others, like Brazil, haven't even slowed the pace of infections. But elsewhere, many countries that took dramatic action to limit the spread of COVID-19 have seen the rate of infections plunge, leaving them with the issue of how to successfully emerge from the restrictions they put in place.

One of those countries is Spain, where infections have dropped from a peak of over 9,000 a day in late March to only about 300 a day at present. Two researchers based in Barcelona (Leonardo López and Xavier Rodó) decided to look at different ways Spain could have exited its restrictions while protecting future public health. After building their model, they set it loose on other countries, including the US. Their work lets us test what might happen if the immunity developed in those infected fades over time or the public's fear of the virus subsides after it's under control.

Lockdown vs. open up

How did Spain get cases in check? In part, by following the advice of public health experts. On March 29, it placed everyone in non-essential jobs on a strict lockdown. Two weeks later, with cases dropping, restrictions started being eased. But the easing was done cautiously, with a variety of restrictions being kept in place as cases continued to drop. López and Rodó were interested in looking at how this reopening could be handled in a way that most effectively limits future returns of widespread infections.

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Posted in Biology, COVID-19, epidemiology, medine, public policy, SARS-CoV-2, science | Comments (0)

Face masks don’t even have to work especially well to be effective

June 12th, 2020
Image of a masked person on a commuter train.

Enlarge / Commuters wear face masks as they travel on the London Underground on June 12, 2020 as lockdown measures are eased during the novel coronavirus COVID-19 pandemic. (credit: TOLGA AKMEN/AFP)

Advice on whether or not to use face masks to limit the spread of the pandemic has varied from country to country, even differing by location within countries. These policies have had to balance whether there were sufficient supplies for medical personnel to divert some to the general public. And the whole issue was decided without a clear idea of whether face masks were actually effective against SARS-CoV-2.

But there has been reason to think masks would at least be somewhat affective, based on studies of the spread of droplets of material we expel while coughing or sneezing. And a recent analysis suggested a large group of individual studies collectively pointed to their effectiveness. But that analysis left a large degree of uncertainty about how effective they'd be at the population level and how face mask use would interact with other policy decisions.

The situation left us needing population-level modeling, which a group of UK scientists has now provided. The group's model indicates that face masks don't have to be especially effective to slow the spread of SARS-CoV-2 and can even bring benefits if they make people more vulnerable to infection. But to really control the pandemic, they will have to be combined with a lockdown if we want to see the total infected population shrink.

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Posted in Biology, COVID-19, epidemiology, face mask, pandemic, SARS-CoV-2, science | Comments (0)

What’s up with Sweden?

June 6th, 2020
State epidemiologist Anders Tegnell of the Public Health Agency of Sweden has admitted that the pandemic response he promotes hasn't worked out as well as he hoped.

Enlarge / State epidemiologist Anders Tegnell of the Public Health Agency of Sweden has admitted that the pandemic response he promotes hasn't worked out as well as he hoped. (credit: ANDERS WIKLUND/Getty Images)

Earlier this week, Sweden's government epidemiologist, Anders Tegnell, admitted that his plans for how the country should handle the SARS-CoV-2 pandemic hasn't quite worked out as he hoped, saying there's "quite obviously a potential for improvement in what we have done," according to one translation. There are probably very few public health officials on the planet who couldn't say the same. But Tegnell's admission made headlines, largely because Sweden has charted its own path, starting with relatively light restrictions compared to other European countries in the hope that the pandemic's economic impact would be blunted.

That approach has turned Sweden into a political talking point far from the Baltic Sea, with many people who would be horrified by Sweden's taxation levels and social safety net suddenly adopting it as a model of minimal government intervention. The role of Sweden in Internet arguments grew increasingly large as opposition to social distancing measures became organized in a number of countries. So, with the country's coronavirus plan architect saying mistakes were made, it's worth taking a look at how Sweden handled the pandemic—and what the results have been.

The plan and its economics

Some countries in Europe, like Italy and Spain, were faced with a rapid surge in cases early in the pandemic; others had the examples of Italy and Spain to guide their policy. The end result was that most European countries imposed pretty severe social distancing regulations, banning large gatherings, closing schools, and limiting access to a variety of businesses. In most cases, this has limited the spread of the pandemic, or at least it started to bring an out-of-control situation back into something more manageable.

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Posted in Biology, COVID-19, epidemiology, Infectious disease, SARS-CoV-2, science, sweden | Comments (0)

Understanding epidemiology models

June 1st, 2020
People walk past a social distancing sign outside the Royal Botanic Garden on May 31, 2020 in Sydney, Australia. Policy decisions to re-open facilities or to encourage citizens to shelter in place don't come out of nowhere—there's often (hopefully) data behind the scenes.

Enlarge / People walk past a social distancing sign outside the Royal Botanic Garden on May 31, 2020 in Sydney, Australia. Policy decisions to re-open facilities or to encourage citizens to shelter in place don't come out of nowhere—there's often (hopefully) data behind the scenes. (credit: James D. Morgan/Getty Images)

One of the least expected aspects of 2020 has been the fact that epidemiological models have become both front-page news and a political football. Public health officials have consulted with epidemiological modelers for decades as they've attempted to handle diseases ranging from HIV to the seasonal flu. Before 2020, it had been rare for the role these models play to be recognized outside of this small circle of health policymakers.

Some of that tradition hasn't changed with the SARS-CoV-2 pandemic. International bodies, individual countries, most states, and even some cities have worked with modelers to try to shape policy responses to the threat of COVID-19. But some other aspects of epidemiological modeling life clearly have changed. The models, some of which produce eye-catching estimates of fatalities, have driven headlines in addition to policy responses. And those policy responses have ended up being far more controversial than anyone might have expected heading into the pandemic.

With the severity of COVID-19, it's no surprise that there has been increased scrutiny of epidemiological models. Models have become yet another aspect of life embroiled in political controversy. And it's fair for the public to ask why different models—or even the same model run a few days apart—can produce dramatically different estimates of future fatalities.

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Posted in Biology, computers science, epidemiology, Features, modeling, science | Comments (0)

3 different countries, 1 result: Stay-at-home orders work

May 18th, 2020
Classes have restarted in France following the lifting of restrictions.

Enlarge / Classes have restarted in France following the lifting of restrictions. (credit: SEBASTIEN BOZON/Getty Images)

The various forms of social restrictions, from distancing to stay-at-home orders, seem like a radical departure to most of us. But faced with a pathogen that spreads through human interactions, they're an obvious potential solution to limit that spread. And a variety of epidemiological models have indicated that various combinations of these approaches should be effective.

But do they actually work in the real, messy, interconnected modern world, and against this specific pathogen? It's important to try to confirm that the models accurately project real-world results, and epidemiologists are doing exactly that. So far, the results are good: across several countries and contexts, restrictions were associated with significant drops in the spread of SARS-CoV-2. The bad news is that more severe restrictions may be necessary to keep the number of infections from increasing.

Good news from France

France was one of a number of countries that went for a lockdown, with anyone found outside their home expected to have a permit explaining why they needed to travel. The country has only just started to ease these restrictions following a period in which the total number of infected individuals has fallen. An international team of researchers has now looked at the dynamics of SARS-CoV-2's spread in the time before and after the lockdown was started on March 17.

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Posted in Biology, epidemiology, pandemic, Policy, SARS-CoV-2, science, social distancing | Comments (0)

Researchers say those recovered from SARS-CoV-2 can be a societal shield

May 14th, 2020
Image of medical samples.

Enlarge / View of blood collection tubes in a rack awaiting SARS-CoV-2 antibody testing. (credit: Getty Images / Barcroft Media)

While many societies remain locked down in various forms of isolation and social distancing, there's a growing population for whom these measures may be irrelevant: those who have had a SARS-CoV-2 infection and cleared it. While we haven't yet ascertained these people's susceptibility to repeated infections, many clearly have antibodies to the virus, and we're finding that some antibodies seem to neutralize the virus. So, there's a reasonable chance that it's safe for these individuals to circulate more widely within the population.

A group of researchers largely based at Georgia Tech have looked at whether this population might be helpful for limiting further infections. The researchers used an epidemiological model to test what would happen if we started placing the formerly infected individuals in the key jobs that we've deemed essential for society to function during social isolation. The results suggest that this "shield immunity" is somewhat effective on its own and significantly enhances the impact of social isolation.

Lots of caveats

As of right now, there are a number of things we don't know about the progression of a viral infection that will be essential for this to work. One is how long it takes for the person to stop being infectious and how that relates to our ability to detect viral RNA in samples from these individuals.

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Posted in epidemiology, immunity, SARS-CoV-2, science | Comments (0)