'It’s Not Whether You Were Exposed to the Virus. It’s How Much.' diff viewer (12/13)

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It’s Not Whether You Were Exposed to the Virus. It’s How Much.	It’s Not Whether You Were Exposed to the Virus. It’s How Much.
2020-06-23 22:54:48 UTC	2020-06-24 15:16:50 UTC (about 16 hours later)
When experts recommend wearing masks, staying at least six feet away from others, washing your hands frequently and avoiding crowded spaces, what they’re really saying is: Try to minimize the amount of virus you encounter.	When experts recommend wearing masks, staying at least six feet away from others, washing your hands frequently and avoiding crowded spaces, what they’re really saying is: Try to minimize the amount of virus you encounter.
A few viral particles cannot make you sick — the immune system would vanquish the intruders before they could. But how much virus is needed for an infection to take root? What is the minimum effective dose?	A few viral particles cannot make you sick — the immune system would vanquish the intruders before they could. But how much virus is needed for an infection to take root? What is the minimum effective dose?
A precise answer is impossible, because it’s difficult to capture the moment of infection. Scientists are studying ferrets, hamsters and mice for clues but, of course, it wouldn’t be ethical for scientists to expose people to different doses of the coronavirus, as they do with milder cold viruses.	A precise answer is impossible, because it’s difficult to capture the moment of infection. Scientists are studying ferrets, hamsters and mice for clues but, of course, it wouldn’t be ethical for scientists to expose people to different doses of the coronavirus, as they do with milder cold viruses.
“The truth is, we really just don’t know,” said Angela Rasmussen, a virologist at Columbia University in New York. “I don’t think we can make anything better than an educated guess.”	“The truth is, we really just don’t know,” said Angela Rasmussen, a virologist at Columbia University in New York. “I don’t think we can make anything better than an educated guess.”
Common respiratory viruses, like influenza and other coronaviruses, should offer some insight. But researchers have found little consistency.	Common respiratory viruses, like influenza and other coronaviruses, should offer some insight. But researchers have found little consistency.
For SARS, also a coronavirus, the estimated infective dose is just a few hundred particles. For MERS, the infective dose is much higher, on the order of thousands of particles.	For SARS, also a coronavirus, the estimated infective dose is just a few hundred particles. For MERS, the infective dose is much higher, on the order of thousands of particles.
The new coronavirus, SARS-CoV-2, is more similar to the SARS virus and, therefore, the infectious dose may be hundreds of particles, Dr. Rasmussen said.	The new coronavirus, SARS-CoV-2, is more similar to the SARS virus and, therefore, the infectious dose may be hundreds of particles, Dr. Rasmussen said.
But the virus has a habit of defying predictions.	But the virus has a habit of defying predictions.
Generally, people who harbor high levels of pathogens — whether from influenza, H.I.V. or SARS — tend to have more severe symptoms and are more likely to pass on the pathogens to others.	Generally, people who harbor high levels of pathogens — whether from influenza, H.I.V. or SARS — tend to have more severe symptoms and are more likely to pass on the pathogens to others.
But in the case of the new coronavirus, people who have no symptoms seem to have viral loads — that is, the amount of virus in their bodies — just as high as those who are seriously ill, according to some studies.	But in the case of the new coronavirus, people who have no symptoms seem to have viral loads — that is, the amount of virus in their bodies — just as high as those who are seriously ill, according to some studies.
And coronavirus patients are most infectious two to three days before symptoms begin, less so after the illness really hits.	And coronavirus patients are most infectious two to three days before symptoms begin, less so after the illness really hits.
Some people are generous transmitters of the coronavirus; others are stingy. So-called super-spreaders seem to be particularly gifted in transmitting it, although it’s unclear whether that’s because of their biology or their behavior.	Some people are generous transmitters of the coronavirus; others are stingy. So-called super-spreaders seem to be particularly gifted in transmitting it, although it’s unclear whether that’s because of their biology or their behavior.
On the receiving end, the shape of a person’s nostrils and the amount of nose hair and mucus present — as well as the distribution of certain cellular receptors in the airway that the virus needs to latch on to — can all influence how much virus it takes to become infected.	On the receiving end, the shape of a person’s nostrils and the amount of nose hair and mucus present — as well as the distribution of certain cellular receptors in the airway that the virus needs to latch on to — can all influence how much virus it takes to become infected.
A higher dose is clearly worse, though, and that may explain why some young health care workers have fallen victim even though the virus usually targets older people.	A higher dose is clearly worse, though, and that may explain why some young health care workers have fallen victim even though the virus usually targets older people.
The crucial dose may also vary depending on whether it’s ingested or inhaled.	The crucial dose may also vary depending on whether it’s ingested or inhaled.
People may take in virus by touching a contaminated surface and then putting their hands on their nose or mouth. But “this isn’t thought to be the main way the virus spreads,” according to the Centers for Disease Control and Prevention.	People may take in virus by touching a contaminated surface and then putting their hands on their nose or mouth. But “this isn’t thought to be the main way the virus spreads,” according to the Centers for Disease Control and Prevention.
That form of transmission may require millions more copies of the virus to cause an infection, compared to inhalation.	That form of transmission may require millions more copies of the virus to cause an infection, compared to inhalation.
Coughing, sneezing, singing, talking and even heavy breathing can result in the expulsion of thousands of large and small respiratory droplets carrying the virus.	Coughing, sneezing, singing, talking and even heavy breathing can result in the expulsion of thousands of large and small respiratory droplets carrying the virus.
“It’s clear that one doesn’t have to be sick and coughing and sneezing for transmission to occur,” said Dr. Dan Barouch, a viral immunologist at Beth Israel Deaconess Medical Center in Boston.	“It’s clear that one doesn’t have to be sick and coughing and sneezing for transmission to occur,” said Dr. Dan Barouch, a viral immunologist at Beth Israel Deaconess Medical Center in Boston.
Larger droplets are heavy and float down quickly — unless there’s a breeze or an air-conditioning blast — and can’t penetrate surgical masks. But droplets less than 5 microns in diameter, called aerosols, can linger in the air for hours.	Larger droplets are heavy and float down quickly — unless there’s a breeze or an air-conditioning blast — and can’t penetrate surgical masks. But droplets less than 5 microns in diameter, called aerosols, can linger in the air for hours.
~~Updated June ~~22,~~ 2020~~	Updated June 24, 2020
	Scientists around the country have tried to identify everyday materials that do a good job of filtering microscopic particles. In recent tests, HEPA furnace filters scored high, as did vacuum cleaner bags, fabric similar to flannel pajamas and those of 600-count pillowcases. Other materials tested included layered coffee filters and scarves and bandannas. These scored lower, but still captured a small percentage of particles.
A commentary published this month on the website of the British Journal of Sports Medicine points out that covering your face during exercise “comes with issues of potential breathing restriction and discomfort” and requires “balancing benefits versus possible adverse events.” Masks do alter exercise, says Cedric X. Bryant, the president and chief science officer of the American Council on Exercise, a nonprofit organization that funds exercise research and certifies fitness professionals. “In my personal experience,” he says, “heart rates are higher at the same relative intensity when you wear a mask.” Some people also could experience lightheadedness during familiar workouts while masked, says Len Kravitz, a professor of exercise science at the University of New Mexico.	A commentary published this month on the website of the British Journal of Sports Medicine points out that covering your face during exercise “comes with issues of potential breathing restriction and discomfort” and requires “balancing benefits versus possible adverse events.” Masks do alter exercise, says Cedric X. Bryant, the president and chief science officer of the American Council on Exercise, a nonprofit organization that funds exercise research and certifies fitness professionals. “In my personal experience,” he says, “heart rates are higher at the same relative intensity when you wear a mask.” Some people also could experience lightheadedness during familiar workouts while masked, says Len Kravitz, a professor of exercise science at the University of New Mexico.
The steroid, dexamethasone, is the first treatment shown to reduce mortality in severely ill patients, according to scientists in Britain. The drug appears to reduce inflammation caused by the immune system, protecting the tissues. In the study, dexamethasone reduced deaths of patients on ventilators by one-third, and deaths of patients on oxygen by one-fifth.	The steroid, dexamethasone, is the first treatment shown to reduce mortality in severely ill patients, according to scientists in Britain. The drug appears to reduce inflammation caused by the immune system, protecting the tissues. In the study, dexamethasone reduced deaths of patients on ventilators by one-third, and deaths of patients on oxygen by one-fifth.
The coronavirus emergency relief package gives many American workers paid leave if they need to take time off because of the virus. It gives qualified workers two weeks of paid sick leave if they are ill, quarantined or seeking diagnosis or preventive care for coronavirus, or if they are caring for sick family members. It gives 12 weeks of paid leave to people caring for children whose schools are closed or whose child care provider is unavailable because of the coronavirus. It is the first time the United States has had widespread federally mandated paid leave, and includes people who don’t typically get such benefits, like part-time and gig economy workers. But the measure excludes at least half of private-sector workers, including those at the country’s largest employers, and gives small employers significant leeway to deny leave.	The coronavirus emergency relief package gives many American workers paid leave if they need to take time off because of the virus. It gives qualified workers two weeks of paid sick leave if they are ill, quarantined or seeking diagnosis or preventive care for coronavirus, or if they are caring for sick family members. It gives 12 weeks of paid leave to people caring for children whose schools are closed or whose child care provider is unavailable because of the coronavirus. It is the first time the United States has had widespread federally mandated paid leave, and includes people who don’t typically get such benefits, like part-time and gig economy workers. But the measure excludes at least half of private-sector workers, including those at the country’s largest employers, and gives small employers significant leeway to deny leave.
So far, the evidence seems to show it does. A widely cited paper published in April suggests that people are most infectious about two days before the onset of coronavirus symptoms and estimated that 44 percent of new infections were a result of transmission from people who were not yet showing symptoms. Recently, a top expert at the World Health Organization stated that transmission of the coronavirus by people who did not have symptoms was “very rare,” but she later walked back that statement.	So far, the evidence seems to show it does. A widely cited paper published in April suggests that people are most infectious about two days before the onset of coronavirus symptoms and estimated that 44 percent of new infections were a result of transmission from people who were not yet showing symptoms. Recently, a top expert at the World Health Organization stated that transmission of the coronavirus by people who did not have symptoms was “very rare,” but she later walked back that statement.
Touching contaminated objects and then infecting ourselves with the germs is not typically how the virus spreads. But it can happen. A number of studies of flu, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can spread by touching contaminated surfaces, particularly in places like day care centers, offices and hospitals. But a long chain of events has to happen for the disease to spread that way. The best way to protect yourself from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing your hands, not touching your face and wearing masks.	Touching contaminated objects and then infecting ourselves with the germs is not typically how the virus spreads. But it can happen. A number of studies of flu, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can spread by touching contaminated surfaces, particularly in places like day care centers, offices and hospitals. But a long chain of events has to happen for the disease to spread that way. The best way to protect yourself from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing your hands, not touching your face and wearing masks.
A study by European scientists is the first to document a strong statistical link between genetic variations and Covid-19, the illness caused by the coronavirus. Having Type A blood was linked to a 50 percent increase in the likelihood that a patient would need to get oxygen or to go on a ventilator, according to the new study.	A study by European scientists is the first to document a strong statistical link between genetic variations and Covid-19, the illness caused by the coronavirus. Having Type A blood was linked to a 50 percent increase in the likelihood that a patient would need to get oxygen or to go on a ventilator, according to the new study.
The unemployment rate fell to 13.3 percent in May, the Labor Department said on June 5, an unexpected improvement in the nation’s job market as hiring rebounded faster than economists expected. Economists had forecast the unemployment rate to increase to as much as 20 percent, after it hit 14.7 percent in April, which was the highest since the government began keeping official statistics after World War II. But the unemployment rate dipped instead, with employers adding 2.5 million jobs, after more than 20 million jobs were lost in April.	The unemployment rate fell to 13.3 percent in May, the Labor Department said on June 5, an unexpected improvement in the nation’s job market as hiring rebounded faster than economists expected. Economists had forecast the unemployment rate to increase to as much as 20 percent, after it hit 14.7 percent in April, which was the highest since the government began keeping official statistics after World War II. But the unemployment rate dipped instead, with employers adding 2.5 million jobs, after more than 20 million jobs were lost in April.
States are reopening bit by bit. This means that more public spaces are available for use and more and more businesses are being allowed to open again. The federal government is largely leaving the decision up to states, and some state leaders are leaving the decision up to local authorities. Even if you aren’t being told to stay at home, it’s still a good idea to limit trips outside and your interaction with other people.
Common symptoms include fever, a dry cough, fatigue and difficulty breathing or shortness of breath. Some of these symptoms overlap with those of the flu, making detection difficult, but runny noses and stuffy sinuses are less common. The C.D.C. has also added chills, muscle pain, sore throat, headache and a new loss of the sense of taste or smell as symptoms to look out for. Most people fall ill five to seven days after exposure, but symptoms may appear in as few as two days or as many as 14 days.	Common symptoms include fever, a dry cough, fatigue and difficulty breathing or shortness of breath. Some of these symptoms overlap with those of the flu, making detection difficult, but runny noses and stuffy sinuses are less common. The C.D.C. has also added chills, muscle pain, sore throat, headache and a new loss of the sense of taste or smell as symptoms to look out for. Most people fall ill five to seven days after exposure, but symptoms may appear in as few as two days or as many as 14 days.
If air travel is unavoidable, there are some steps you can take to protect yourself. Most important: Wash your hands often, and stop touching your face. If possible, choose a window seat. A study from Emory University found that during flu season, the safest place to sit on a plane is by a window, as people sitting in window seats had less contact with potentially sick people. Disinfect hard surfaces. When you get to your seat and your hands are clean, use disinfecting wipes to clean the hard surfaces at your seat like the head and arm rest, the seatbelt buckle, the remote, screen, seat back pocket and the tray table. If the seat is hard and nonporous or leather or pleather, you can wipe that down, too. (Using wipes on upholstered seats could lead to a wet seat and spreading of germs rather than killing them.)	If air travel is unavoidable, there are some steps you can take to protect yourself. Most important: Wash your hands often, and stop touching your face. If possible, choose a window seat. A study from Emory University found that during flu season, the safest place to sit on a plane is by a window, as people sitting in window seats had less contact with potentially sick people. Disinfect hard surfaces. When you get to your seat and your hands are clean, use disinfecting wipes to clean the hard surfaces at your seat like the head and arm rest, the seatbelt buckle, the remote, screen, seat back pocket and the tray table. If the seat is hard and nonporous or leather or pleather, you can wipe that down, too. (Using wipes on upholstered seats could lead to a wet seat and spreading of germs rather than killing them.)
If you’ve been exposed to the coronavirus or think you have, and have a fever or symptoms like a cough or difficulty breathing, call a doctor. They should give you advice on whether you should be tested, how to get tested, and how to seek medical treatment without potentially infecting or exposing others.	If you’ve been exposed to the coronavirus or think you have, and have a fever or symptoms like a cough or difficulty breathing, call a doctor. They should give you advice on whether you should be tested, how to get tested, and how to seek medical treatment without potentially infecting or exposing others.
If you’re sick and you think you’ve been exposed to the new coronavirus, the C.D.C. recommends that you call your healthcare provider and explain your symptoms and fears. They will decide if you need to be tested. Keep in mind that there’s a chance — because of a lack of testing kits or because you’re asymptomatic, for instance — you won’t be able to get tested.
“They travel further, last longer and have the potential of more spread than the large droplets,” Dr. Barouch said.	“They travel further, last longer and have the potential of more spread than the large droplets,” Dr. Barouch said.
Three factors seem to be particularly important for aerosol transmission: proximity to the infected person, air flow and timing.	Three factors seem to be particularly important for aerosol transmission: proximity to the infected person, air flow and timing.
A windowless public bathroom with high foot traffic is riskier than a bathroom with a window, or a bathroom that’s rarely used. A short outdoor conversation with a masked neighbor is much safer than either of those scenarios.	A windowless public bathroom with high foot traffic is riskier than a bathroom with a window, or a bathroom that’s rarely used. A short outdoor conversation with a masked neighbor is much safer than either of those scenarios.
Recently, Dutch researchers used a special spray nozzle to simulate the expulsion of saliva droplets and then tracked their movement. The scientists found that just cracking open a door or a window can banish aerosols.	Recently, Dutch researchers used a special spray nozzle to simulate the expulsion of saliva droplets and then tracked their movement. The scientists found that just cracking open a door or a window can banish aerosols.