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When Is The Best Time To Get Tested For COVID-19 Before Traveling?

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COVID-19: When To Use At-Home Testing Kits


Traveling this pandemic? A new study showed that testing for COVID right before leaving is the best thing to do. 

For the study published in the International Journal of Public Health, the team of epidemiologists from Yale School of Public Health were the first to use statistical analysis to figure out how effective test-timing strategies are at limiting COVID-19 spread. The team found that testing on the day of an event/outing can nearly halve the risk of transmitting the virus.

The team also stated that policies requiring people to have a negative COVID test within 72 hours or more on arrival at a location – something most countries require for travelers – are hardly helpful.

According to senior author Jeffrey Townsend, the Elihu Professor of Biostatistics at the Yale School of Public Health, this is because the virus grows exponentially in the human body. Taken early enough, a rapid-antigen (RA) test can fail to detect faint traces of the virus before it builds up enough to result in a positive test. This means in just a matter of hours, someone unknowingly infected but tested negatively could spread the virus to other people.

“Typically, the disease has a very short period where it is really highly transmissible. Go back just a little bit of time and there’s often hardly any virus in you, compared to just a little later, when your viral load could be surging,” said Townsend.

To understand how transmission changes with testing at different times, Townsend and his colleagues applied mathematical modeling. Per the study, the probability that a person with COVID would transmit the virus to one or more individuals after the start of an event is roughly 40% without any testing. However, as testing is performed closer and closer to arrival time, that risk drops more and more.

“We’re not the first people to say that you should test closer to an event . But this study really nails it down: it matters an enormous amount—and here’s the curve that shows it,” Townsend added.

As part of their analysis, the team analyzed more than a dozen different RA home tests and found that they are more effective than RT-PCR tests since they provide quick results. 





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Not Just Pests: Bed Bugs Produce This Chemical In Large Amounts, Study Finds

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Not Just Pests: Bed Bugs Produce This Chemical In Large Amounts, Study Finds


Bed bugs may not only be unwanted visitors in our homes and beds but also creatures harboring a hidden risk. A team of researchers has found that they may actually be producing amounts of histamine that may potentially be problematic for humans.

Bed bugs are tiny, parasitic insects that can be found all over the world. At just 1 to 7 millimeters, they feed on people’s and animals’ blood and have been “spreading rapidly” in places like the U.S., Canada, the U.K. and some parts of Europe. They can be found even in hotels and resorts.

For their study, published in the Journal of Medical Entomology, a team of researchers analyzed the fecal materials that bed bugs deposit at different stages of their lives.

“Following a blood meal, bed bugs deposit fecal material indoors. The feces contain a variety of compounds, including histamine, which serves as a component of their aggregation pheromone,” they wrote. “Histamine is a pivotal mammalian immune modulator, and recently it was shown to be present in high concentrations in household dust from homes infested with bed bugs.”

Histamine is a chemical in the human body that can alert the immune system to threats and trigger inflammation, the University of Kentucky (UK) noted in a news release. While production of it normally leads to allergic reactions resulting in rashes or respiratory issues, an excess of histamine has been linked to reactions such as headaches, asthma and irregular heart rate, particularly among those with histamine intolerance.

The researchers found variations in bed bugs’ histamine production in different life stages, but that “overall,” they produce histamine “across all feeding life stages, populations and at various times after feeding, and that histamine excretion is directly related to blood feeding.”

And the amount of histamine they can produce is no joke, with one bed bug capable of producing over 50 micrograms in a week. If there are 1,000 bed bugs in an infestation, they may produce 40 milligrams of histamine in a week, and 2 grams in a year, according to the university.

“That’s an amount you can actually see, and we don’t see that with any other containment,” one of the study leads, Zach DeVries of UK, said in the news release. “When we talk about pesticides, allergens, any other thing in our home that some invading organism is producing, it’s always on microscopic levels, not something where you could actually hold it in your hand.”

More research needs to be done to find out the exact implications of the findings on human health, according to the researchers. It does, however, show that even if bed bugs aren’t known to carry pathogens and spread disease as other bugs do, they may still be carrying potential risks beyond being annoying pests and the occasional allergic reaction to their bites.

“It’s not only the fact that they’re producing histamine, but they’re producing it right next to where you spend the most time, generally speaking, within our homes, which is in our beds or sleeping areas,” De Vries said.

“These results will be used to better understand the health risks associated with histamine excretion and potential mitigation strategies of environmental histamine,” the researchers wrote.





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Stressed? Your Dog May Actually Be Able To Smell It In Your Breath, Sweat

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Dog Ownership Protects Against Disability In Older People: Study


t is easy for your dog to know if you’re stressed, and that’s because it may smell it in your breath and sweat, according to a new study.

Previous studies have suggested that dogs can tell if people are stressed, a team of researchers wrote in their study, published Wednesday in PLOS (Public Library of Science) ONE. Since dogs are known to have an incredible sense of smell, the researchers sought to find whether may actually be sensing the stress through chemical signals, PLOS noted in a news release.

So for their work, the researchers conducted an experiment to see whether dogs can differentiate between human odors at baseline (neutral) and when they’re under stress. To do this, they collected breath and sweat samples from participants at baseline and after they had gone through a stress-inducing arithmetic task. Their stress was also validated through self-report, as well as measures such as their blood pressure and heart rate.

Samples from 36 participants were presented to trained dogs within three hours of being collected.

“In Phase One, the dog was presented with a participant’s stress sample (taken immediately post-task) alongside two blanks (the sample materials without breath or sweat), and was required to identify the stress sample with an alert behavior,” the researchers explained. “In Phase Two, the dog was presented with the stress sample, the same participant’s baseline sample (taken pre-task), and a blank.”

This photo shows the dogs during the experiments.

The idea is that if the dogs could correctly identify the stress samples in Phase Two, when the baseline samples of the participant were also around, then the baseline and stress odors were actually distinguishable to them, the researchers explained.

Incredibly, the dogs were individually able to detect the stress samples and perform the alert behavior with an impressive accuracy ranging from 90% to 96.88%. Their combined accuracy was 93.75%. This, according to the researchers, is “greater than expected by chance.”

“While the dogs in this study underwent training in order to communicate that they were able to distinguish between odors, the found performances on this task suggests that there are VOC (volatile organic compound) changes induced by acute negative stress that are detectable by dogs,” they wrote.

In other words, the results suggest that dogs can actually detect the changes in people’s breath and sweat when they’re psychologically stressed, and they can do so “with a high degree of accuracy.”

Not only does this shed further light on the relationship between dogs and humans, but they say it may also have implications for service dogs that, according to PLOS, are so far trained to respond mainly to visual cues.





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Study Confirms Link Between COVID-19 Vaccination And Increased Menstrual Cycle Length

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Does COVID-19 Vaccination Affect Women’s Menstrual Cycle?


COVID-19 vaccination does lead to an average increase in menstrual cycle length, according to a new large international study. 

The study funded by the National Institutes of Health (NIH) found that women experienced a longer menstrual cycle length after getting vaccinated against SARS-CoV-2. 

The slight increase was less than one day, so there was no notable change to the number of days of menses (days of bleeding), the NIH said in a press release published Tuesday. 

Based on the study findings, the increase was consistent across data from around 20,000 female participants in Canada, the United Kingdom and other parts of Europe and the world. 

Alison Edelman, M.D., M.P.H., the study’s principal investigator spoke about the team’s findings with The Washington Post. According to her, the vaccination effects were temporary, so they did not impact the fertility of the participants. 

“Now we can give people information about possibly what to expect with menstrual cycles. So I hope that’s overall really reassuring to individuals,” the professor of obstetrics and gynecology at Oregon Health & Science University added. 

Edelman admitted that her team was still unsure why the vaccination affected the menstrual cycles of the participants, but she noted that the immune and reproductive systems have a connection. 

Per the team’s collected data, the participants’ menstrual cycles increased by less than 24 hours after the first COVID-19 vaccine dose and by around half a day after the second dose. 

Once they completed the vaccination series, their menstrual cycle mostly returned to its normal length for those who received one dose per menstrual cycle. 

The researchers collected data using the fertility tracking app called Natural Cycles. Participants provided information on their temperature and menstrual cycle length via the app, according to CNBC.

The new study confirmed the findings of a previous U.S. study published in January that first linked COVID-19 vaccination with an increased menstrual cycle length. 

“These findings provide additional information for counseling women on what to expect after vaccination. Changes following vaccination appear to be small, within the normal range of variation, and temporary,” said Diana Bianchi, M.D., director of NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development.





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