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Modeling the influence of COVID superspreading events

Study: Exploring the Role of Superspreading Events in SARS-CoV-2 Outbreaks. Image Credit: StockTom / Shutterstock

In a recent study posted to the medRxiv* preprint server, University of Kansas researchers assessed the effect of superspreading events (SSEs) on the United States (US) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak dynamics.

Study: Exploring the Role of Superspreading Events in SARS-CoV-2 Outbreaks. Image Credit: StockTom / ShutterstockStudy: Exploring the Role of Superspreading Events in SARS-CoV-2 Outbreaks. Image Credit: StockTom / Shutterstock


SARS-CoV-2, the novel coronavirus that emerged in late December 2019, has quickly swept over the globe, resulting in over 546 million illnesses and more than 6.3 million fatalities thus far. Coronavirus disease 2019 (COVID-19) has strained the US healthcare network, with several hospitals exceeding or nearing capacity and few limiting services. 

Governments at the state and national levels have responded by issuing guidelines and regulations for decreasing SARS-CoV-2 transmission, including social-distancing directives, mask mandates, stay-at-home instructions, and restrictions on big gatherings. However, insufficient adherence and compliance by the population have affected the efficiency of these laws and regulations, encouraging SSEs, which have assisted the SARS-CoV-2 transmission.

About the study

In the present study, the researchers developed a continuous-time Markov chain (CTMC) model to examine the impact of SSEs on the dynamics of the SARS-CoV-2 outbreak in the US. The authors defined SSEs as social or public events that lead to numerous SARS-CoV-2 infections over a short period.

The current research sought to determine the effect of SSEs compared to non-SSEs on COVID-19 outbreak dynamics, the efficacy of hospitalization and quarantine as containment methods for SSE relative to non-SSE-dominated outbreaks, and the impact of quarantine violation on the efficacy of quarantine for SSE compared to non-SSE-dominated outbreaks.

The investigators simulated a CTMC model for SARS-CoV-2 spread utilizing Gillespie’s direct algorithm under three distinct scenarios: 1) neither hospitalization nor quarantine; 2) quarantine, hospitalization, premature hospital discharge, and quarantine violation; and 3) hospitalization and quarantine but not premature hospital discharge or quarantine violation. They also alter the rate of quarantine violations under realistic hospitalization and quarantine (RHQ) scenarios.


The study results demonstrated that the SARS-CoV-2 outbreaks with SSE dominance were often more variable yet less severe and more prone to extinction than outbreaks without SSE dominance. The authors observed this after eliminating hospitalization and quarantine conditions or upon the inclusion of hospitalization, quarantine, early hospital discharge, and quarantine breach. 

However, the severity of the most catastrophic SSE-dominated outbreaks was higher than the most severe outbreaks without SSE dominance, despite most SSE-dominated outbreaks being less severe. Upon the inclusion of quarantine and hospitalization, while excluding quarantine breach and premature hospital discharge, SARS-CoV-2 outbreaks dominated by SSE were more susceptible to extinction than outbreaks without SSE dominance but were more severe and less variable.

Upon the inclusion of quarantine, hospitalization, premature hospital discharge, and halved quarantine breach, outbreaks dominated by SSE were comparable to when quarantine and hospitalization were included, but quarantine breach and premature hospital discharge were excluded. Besides, when quarantine breach was doubled outbreaks were similar to when quarantine and hospitalization were excluded.

Quarantine and hospitalization were more potent at regulating outbreaks dominated by SSE than those without SSE dominance in all scenarios. Similarly, quarantine breaches and premature hospital discharge were significant for outbreaks dominated by SSE.

SSE-dominated outbreaks were extremely improbable to become extinct when quarantine and hospitalization were excluded. They were moderately unlikely to become extinct when quarantine, hospitalization, premature hospital discharge, and quarantine violation were included. Furthermore, they were highly plausible to become extinct when hospitalization and quarantine were included, but quarantine breach and premature hospital discharge were excluded. 

Moreover, SSE-dominated outbreaks were more likely to become extinct when quarantine violations were halved. However, outbreaks dominated by SSE were less likely to become extinct when quarantine breaches were doubled.


Altogether, the study findings showed that COVID-19 outbreaks dominated by SSE differ noticeably from non-SSE-dominated outbreaks in their severity, variability, and chances of extinction. They also vary, albeit more low-key, from outbreaks dominated by superspreading individuals (SI). The possibility of hospitalization or quarantine and the likelihood of premature hospital discharge or violation of quarantine significantly impact the dynamics of SSE-dominated outbreaks.

Hospitalization and quarantine were substantially effective preventative interventions for COVID-19 outbreaks dominated by SSE. Nevertheless, premature hospital discharge and breach of the quarantine drastically diminished their efficacy. Besides, the team assessed control techniques using the probability of extinction.

The present findings have significant public health consequences, necessitating SARS-CoV-2 modelers must: 1) assess the contribution of SSEs or SIs to COVID-19 spread; and 2) differentiate between SSEs, SIs, and non-SIs/non-SSEs in their models. More research into the combined and individual effects of SSEs and SIs on SARS-CoV-2 outbreak dynamics and the efficacy of control strategies for various kinds of outbreaks were required to guide eradication and containment initiatives.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

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New Research Considers Climate Influence on Five Extreme Weather Events Worldwide – EcoWatch

Flooding from Hurricane Ida in Louisiana

Flooding from Hurricane Ida in Louisiana on Sep. 3, 2021. JONATHAN ERNST/POOL/AFP via Getty Images

Whenever an extreme weather event like a heat wave or hurricane occurs, it is typically followed by discussion of the degree to which it was augmented by the climate crisis

Now, a new study published in Environmental Research Climate Wednesday moves beyond individual events to paint a comprehensive picture of how climate change is or is not influencing weather disasters on a global scale. 

“I think on the one hand we overestimate climate change because it’s now quite common that every time an extreme event happens, there is a big assumption that climate change is playing a big role, which is not always the case,” lead author Friederike Otto, who works as a professor of climate change and environment at Imperial College, London’s, Grantham Institute told The Guardian. “But on the other hand, we really underestimate those events where climate change does play a role in what the costs are, especially the non-economic costs of extreme weather events to our societies.”

The researchers looked at five types of extreme weather events: heat waves, wildfires, heavy rainfall, drought and tropical cyclones. They used a combination of attribution studies that assess the impact of the climate crisis on extreme weather events and the latest reports from the Intergovernmental Panel on Climate Change, according to a press release from IOP Publishing. 

What they found is that certain extreme weather events are clearly attributable to climate change. These include heat waves — which have led to tens of thousands of deaths — and rainfall from tropical cyclones in the Atlantic Basin, which has had a price tag of half a trillion dollars, according to the study. 

Other events depend on the region. The California drought, for example, has certainly been worsened by the burning of greenhouse gas emissions. But, in other parts of the world, droughts are caused primarily by local, social factors and so focusing on a potential climate signal is less helpful. 

“By focusing too much on climate change, it really takes the responsibility, but also the agency, away to address these local drivers of disasters such as high poverty rates, missing infrastructure, investment, missing healthcare system… all these aspects of exposure and vulnerability that make every drought a catastrophe,” Otto told The Guardian. 

The research team, which comes from the University of Oxford and the Victoria University of Wellington in addition to Imperial College, London, also emphasized the need for more weather data from poorer countries who are more likely to suffer the impacts of climate change and extreme weather, according to the press release. For example Somalia, which frequently suffers from drought, also has spotty data because recording is interrupted by frequent conflict. 

Senior State meteorologist and head of Climate Assessment and Modeling at the Spanish State Meteorological Agency (AEMET) Ernesto Rodríguez Camino, who was not involved in the research, said in a statement that attribution studies require two things: models of the extreme weather event being studied and on-the-ground observations. 

“Limited access to observations has limited and continues to limit further attribution studies to prepare affected sectors for increasingly frequent and intense weather extremes, a consequence of ongoing anthropogenic climate change,” he said. 

The study’s authors ultimately valorized the importance of such studies, however. 

“Understanding the role that climate change plays in these events can help us better prepare for them. It also allows us to determine the real cost that carbon emissions have in our lives,” lead author Ben Clarke from the University of Oxford said in the press release. 

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Life events that influence estrogen levels may be linked to woman’s dementia risk in later life

Life events that influence estrogen levels may be linked to woman's dementia risk in later life

Life events that influence levels of the female hormone estrogen may be linked to a woman’s risk of developing dementia in later life, according to new research.

The analysis found that some reproductive events – like an early or late start to menstruation, early menopause and hysterectomy – were linked to higher risk of dementia while ever having been pregnant or having had an abortion and later menopause were linked to lower risk.

But childbearing was not one of them, with a similar relationship observed between the number of children and dementia risk in men and women.

Lead author Jessica Gong from The George Institute for Global Health said that although it appeared reproductive events related to changes in hormone levels in women may be involved in dementia risk, the exact relationship was still unknown.

“While the risk of developing dementia increases with age, we don’t yet know whether the higher rates seen in women are simply because they live longer,” explained Ms Gong. “But it’s possible that female-specific reproductive factors may be able to explain some of the sex differences.”

Dementia is fast becoming a global epidemic, currently affecting an estimated 50 million people worldwide. This is projected to triple by 2050 – mainly driven by aging populations. Rates of dementia and associated deaths are both known to be higher in women than men.

Estradiol is the most predominant form of estrogen during reproductive life (from the start of menstruation to menopause) and estriol is the primary estrogen during pregnancy. Use of hormones that originate from outside the body, such as oral contraceptives during reproductive years, and hormone replacement therapy (HRT) in later life can also influence estrogen levels.

To examine these relationships in more detail, George Institute researchers analyzed data on a total of 273,240 women without dementia who were registered with the UK Biobank, a large-scale biomedical database. After adjusting for other factors that could have influenced the results, they found the following were associated with an increased risk of dementia:

  • Early and late first occurrence of menstruation, younger age at first birth, and hysterectomy – specifically hysterectomy without surgical removal of one or both ovaries, or if the hysterectomy took place after ovary removal.

Conversely, the factors associated with a decreased risk were ever having been pregnant, ever having had an abortion, longer reproductive lifespan and later menopause.

“With regard to external hormones, the use oral contraceptive pills was associated with a lower risk of dementia, but our study findings did not support an association between HRT and dementia risk,” Ms Gong said.

The authors proposed that risk variation in women may not be associated with childbearing because a similar pattern was observed between number of children fathered and dementia risk among a similar number men in the same study.

“We found that the higher dementia risk linked to early (natural and artificial) menopause was more pronounced in women of lower socioeconomic status,” she added.

“Social deprivation is likely to be an important determinant of dementia risk as well as other aspects of women’s health.”

With dementia on the rise and in the absence of significant treatment breakthroughs, the focus has been on reducing the risk of developing the disease.

“More research is needed to understand whether these differences are associated with life-long exposure to the body’s own estrogen, and whether external hormone use could influence the risk of developing dementia,” added Ms Gong.

“Our findings may be helpful for identifying high-risk women to participate in future clinical trials to assess potential preventive measures and treatments.”


Journal reference:

Gong, J., et al. (2022) Reproductive factors and the risk of incident dementia: A cohort study of UK Biobank participants. PLOS Medicine.

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Pope’s visit to Kyiv can influence course of events – Yermak

Pope's visit to Kyiv can influence course of events - Yermak

Pope Francis’ visit to Kyiv can influence the course of events concerning Russia’s war against Ukraine.

The head of the Ukrainian President’s Office, Andriy Yermak, said this in a Facebook post, Ukrinform reports.

Yermak recalled that the pontiff had previously addressed world leaders with a message “to end the war before it destroys humanity.”

“Meanwhile, Moscow demonstrates that there is nothing sacred for them in their war against Ukraine. The Pope’s personal visit to Kyiv can influence the course of events. It will further emphasize on whose side civilization is and who represents light in this war,” he said.

He added that light always overcomes darkness. “And the light is Ukraine, our soldiers and our people,” Yermak said.

Pope Francis said earlier that he was considering visiting the Ukrainian capital.

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Reduced kidney function caused by antithrombotic therapy can influence bleeding events

Reduced kidney function caused by antithrombotic therapy can influence bleeding events

Antithrombotic therapy is prescribed to prevent thrombotic (blood clotting inside a blood vessel) events but the treatment also increases the likelihood of experiencing a bleeding event, which can be extremely serious if it occurs in a vital organ. Aging societies tend to have an increased number of patients undergoing antithrombotic therapy, and the drugs used in this treatment can affect kidney function. In particular, reduced kidney function caused by antithrombotic medications can significantly influence bleeding events. It is highly recommended that patients, especially those with decreased kidney function, have a detailed discussion with their doctor about the possible risks and benefits of proceeding with antithrombotic therapy.

Patients with heart arrythmia (atrial fibrillation) have a high risk for thrombotic events in blood vessels that could lead to permanent organ damage-;such as cerebral infarction-;and are prescribed antithrombotic therapy to lower their risk of developing blood clots. However, the risk of bleeding events simultaneously increases due to the nature of these medications. The severity of these bleeding events is highly variable, ranging from epistaxis (nosebleeds) to fatal brain hemorrhage.

While kidney function is known to be related to bleeding event risk, researchers at Kumamoto, Miyazaki, and Tohoku Universities in Japan conducted a post-hoc subgroup analysis of the Atrial Fibrillation and Ischemic Events with Rivaroxaban in Patients with Stable Coronary Artery Disease (AFIRE) trial to determine the impact of kidney function on the risk of recurrent bleeding events during antithrombotic therapy. Their analysis revealed that the effect of kidney function on recurrent bleeding risk events was quite large for patients undergoing this treatment. They also found that the bleeding risk decreased with time for patients with healthy kidney function but remained high for patients with decreased kidney function. Clearly, the decision to use such a therapy should be balanced between the expected antithrombotic effects and bleeding risks.

In most cases, it is considered better to continue antithrombotic therapies even after bleeding events as long as the event was not severe. However, it is not surprising that both patients and physicians hesitate to continue the therapy after any bleeding event. To assess for drug safety and efficacy, these drugs are usually measured by the numbers of bleeding and thrombotic events. Unfortunately, in the assessment of antithrombotic therapy, most studies only consider the first event in their analyses even though patients could experience multiple events throughout their lifetime. This study revealed that the impact of kidney function on bleeding risk during antithrombotic therapy is larger than estimated in previous studies. Furthermore, patients with healthy kidney function appear to have a decreased risk of experiencing a bleeding event over time, but the risk for patients with reduced kidney function remains high as time continues.

A detailed discussion between patients and physicians based on all current scientific evidence about the risks and benefits of antithrombotic therapy is highly recommended. Our analysis should be quite useful in facilitating this type of discussion.”

Dr. Kunihiko Matsui, Study Leader, Kumamoto University Hospital’s Department of General Medicine and Primary Care


Journal reference:

Matsui, K., et al. (2022) The impact of kidney function in patients on antithrombotic therapy: a post hoc subgroup analysis focusing on recurrent bleeding events from the AFIRE trial. BMC Medicine.