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| Don’t Think You Need a Coronavirus Test? What if I Paid You? | Don’t Think You Need a Coronavirus Test? What if I Paid You? |
| (7 days later) | |
| In March, Andrew Atkeson, an economics professor at the University of California, Los Angeles, tried to assess the mortality rate from the new coronavirus based on what is known about its spread. | In March, Andrew Atkeson, an economics professor at the University of California, Los Angeles, tried to assess the mortality rate from the new coronavirus based on what is known about its spread. |
| Does it kill 1 percent of those infected, roughly the case fatality rate on the Diamond Princess cruise ship? Or might it be closer to 0.1 percent, the mortality rate in the United States from the common flu? | Does it kill 1 percent of those infected, roughly the case fatality rate on the Diamond Princess cruise ship? Or might it be closer to 0.1 percent, the mortality rate in the United States from the common flu? |
| If two-thirds of the population becomes infected, as would be needed to achieve what is known as “herd immunity,” the difference between those mortality rates would amount to two million deaths nationwide. | If two-thirds of the population becomes infected, as would be needed to achieve what is known as “herd immunity,” the difference between those mortality rates would amount to two million deaths nationwide. |
| But the answer was elusive. “I wanted to see if we can estimate where we are,” Mr. Atkeson said. “I realized no, we can’t.” | But the answer was elusive. “I wanted to see if we can estimate where we are,” Mr. Atkeson said. “I realized no, we can’t.” |
| He was missing one critical number: the infection rate in the general population. Three economists — Magne Mogstad and Alexander Torgovitsky of the University of Chicago and Andres Santos of U.C.L.A. — have devised a technique to provide it, by figuring out how to coax even people who believe they are healthy into taking a test for the coronavirus. | He was missing one critical number: the infection rate in the general population. Three economists — Magne Mogstad and Alexander Torgovitsky of the University of Chicago and Andres Santos of U.C.L.A. — have devised a technique to provide it, by figuring out how to coax even people who believe they are healthy into taking a test for the coronavirus. |
| Short of testing everybody — an onerous exercise, even if enough test kits were available — figuring out the infection rate across the population requires a representative sample. The sample will include sick people clamoring to be tested but also people who have little interest in going through the ordeal. | Short of testing everybody — an onerous exercise, even if enough test kits were available — figuring out the infection rate across the population requires a representative sample. The sample will include sick people clamoring to be tested but also people who have little interest in going through the ordeal. |
| That raises a problem. In Iceland, which performed tests on a big share of its population, researchers said the results might have been skewed because those concerned about potential infection were more likely to take part. | That raises a problem. In Iceland, which performed tests on a big share of its population, researchers said the results might have been skewed because those concerned about potential infection were more likely to take part. |
| Mr. Mogstad, Mr. Torgovitsky and Mr. Santos figured a way around this constraint: Offer prizes to encourage those who believe themselves healthy to get a test anyway. | Mr. Mogstad, Mr. Torgovitsky and Mr. Santos figured a way around this constraint: Offer prizes to encourage those who believe themselves healthy to get a test anyway. |
| The method is crafty. Say you split the sample into 11 equal random slices and offer people in each a reward. For simplicity, say the reward for taking the test scales up from nothing in the first group to $200. This method would yield the share of people who would take the test for nothing, the share who would do it for $20 and so forth. | The method is crafty. Say you split the sample into 11 equal random slices and offer people in each a reward. For simplicity, say the reward for taking the test scales up from nothing in the first group to $200. This method would yield the share of people who would take the test for nothing, the share who would do it for $20 and so forth. |
| To figure out who would take the test for $100 but not for $80, you would subtract the share of people who responded to the $80 reward from those who took it for $100. The infection rates for the group could be computed in a similar fashion, to reveal the pattern about how testing changes and the infection rate changes as rewards increase. | To figure out who would take the test for $100 but not for $80, you would subtract the share of people who responded to the $80 reward from those who took it for $100. The infection rates for the group could be computed in a similar fashion, to reveal the pattern about how testing changes and the infection rate changes as rewards increase. |
| There are likely to be people who decline to take the test even at the highest reward. But the researchers can approximate their infection rate by extrapolating from the information they have. If they know how the participation rate and the odds of testing positive change as the reward rises from $160 to $180 to $200, they can deduce what the results would be at $220 and $300. | There are likely to be people who decline to take the test even at the highest reward. But the researchers can approximate their infection rate by extrapolating from the information they have. If they know how the participation rate and the odds of testing positive change as the reward rises from $160 to $180 to $200, they can deduce what the results would be at $220 and $300. |
| The underlying assumption is that people’s behavior changes smoothly as incentives change. If that holds, the researchers could construct a decent estimate of the infection rate in all or most of the population. | The underlying assumption is that people’s behavior changes smoothly as incentives change. If that holds, the researchers could construct a decent estimate of the infection rate in all or most of the population. |
| As the virus becomes more and more prevalent across countries, such testing will become critical. “What is the probability that if I go to the store I will become infected?” asked Marc Suchard, a professor of biomathematics at U.C.L.A. “You can’t nail that down without knowing the underlying rate of infection.” | As the virus becomes more and more prevalent across countries, such testing will become critical. “What is the probability that if I go to the store I will become infected?” asked Marc Suchard, a professor of biomathematics at U.C.L.A. “You can’t nail that down without knowing the underlying rate of infection.” |
| Notably, as Mr. Atkeson found out, it’s hard to tell what share of infected people die from the virus if you don’t know how many have had it. You could get the same number of deaths with a high mortality rate and a low infection rate or the other way around, if the virus propagated very fast but killed fewer people. | Notably, as Mr. Atkeson found out, it’s hard to tell what share of infected people die from the virus if you don’t know how many have had it. You could get the same number of deaths with a high mortality rate and a low infection rate or the other way around, if the virus propagated very fast but killed fewer people. |
| Different findings would call for different strategies. A slow spread with a high death rate might suggest the containment policies deployed around the world are working, and would support maintaining a strict lockdown. The alternative could suggest that more people have some resistance to the virus and support relaxing quarantines across U.S. cities and states. | Different findings would call for different strategies. A slow spread with a high death rate might suggest the containment policies deployed around the world are working, and would support maintaining a strict lockdown. The alternative could suggest that more people have some resistance to the virus and support relaxing quarantines across U.S. cities and states. |
| “Distinguishing between these two scenarios is key,” Mr. Mogstad said. | “Distinguishing between these two scenarios is key,” Mr. Mogstad said. |
| And yet nobody has measured this statistic. Countries testing for the virus have mostly focused on testing people suspected of being sick — people with symptoms and those who have come into contact with them. | And yet nobody has measured this statistic. Countries testing for the virus have mostly focused on testing people suspected of being sick — people with symptoms and those who have come into contact with them. |
| Take the National Institutes of Health. In a two-year study about to begin, it will perform an antibody test on 10,000 volunteers from around the country. The number is large. But the N.I.H. decided to apply it on an “opt in” basis, to anybody who asked for it, so it will not amount to a representative sample of the population. | Take the National Institutes of Health. In a two-year study about to begin, it will perform an antibody test on 10,000 volunteers from around the country. The number is large. But the N.I.H. decided to apply it on an “opt in” basis, to anybody who asked for it, so it will not amount to a representative sample of the population. |
| It will represent only those who want it most, capturing mostly Americans who fear they are sick. It will miss many asymptomatic carriers of the virus, who see no point in getting tested. The exercise will then fail to provide a faithful picture of how the new coronavirus has spread across the country. | It will represent only those who want it most, capturing mostly Americans who fear they are sick. It will miss many asymptomatic carriers of the virus, who see no point in getting tested. The exercise will then fail to provide a faithful picture of how the new coronavirus has spread across the country. |
| Updated July 7, 2020 | |
| The coronavirus can stay aloft for hours in tiny droplets in stagnant air, infecting people as they inhale, mounting scientific evidence suggests. This risk is highest in crowded indoor spaces with poor ventilation, and may help explain super-spreading events reported in meatpacking plants, churches and restaurants. It’s unclear how often the virus is spread via these tiny droplets, or aerosols, compared with larger droplets that are expelled when a sick person coughs or sneezes, or transmitted through contact with contaminated surfaces, said Linsey Marr, an aerosol expert at Virginia Tech. Aerosols are released even when a person without symptoms exhales, talks or sings, according to Dr. Marr and more than 200 other experts, who have outlined the evidence in an open letter to the World Health Organization. | |
| 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. |
| 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. | 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. |
| 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. |
| There is other valuable testing to be done. Some health experts argue that, early in an epidemic, it is more useful to test specifically those suspected of carrying the virus, to trace their contacts and introduce more nuanced separation and quarantining policies. | There is other valuable testing to be done. Some health experts argue that, early in an epidemic, it is more useful to test specifically those suspected of carrying the virus, to trace their contacts and introduce more nuanced separation and quarantining policies. |
| “I don’t care about the prevalence of the infection in the population,” said Stefano Bertozzi, a professor of health policy and management at the University of California, Berkeley, who was the last director of the World Health Organization Global Program on AIDS. “I care about when the infection rate will overwhelm the capacity of the health system.” | “I don’t care about the prevalence of the infection in the population,” said Stefano Bertozzi, a professor of health policy and management at the University of California, Berkeley, who was the last director of the World Health Organization Global Program on AIDS. “I care about when the infection rate will overwhelm the capacity of the health system.” |
| There are more urgent questions at this stage than the overall infection rate in the population, he noted. For instance, what is the share of infected people who get sick, and how fast is the infection rate growing across thousands of cities? There is hope that epidemiological modeling based on testing of infected people can approximate this answer effectively, he said. | There are more urgent questions at this stage than the overall infection rate in the population, he noted. For instance, what is the share of infected people who get sick, and how fast is the infection rate growing across thousands of cities? There is hope that epidemiological modeling based on testing of infected people can approximate this answer effectively, he said. |
| And yet, Mr. Mogstad argued, tracking the infection rate in the population is essential to track the evolution of the virus, including asymptomatic cases, and how it affects people of different races and income levels. That is critical to deciding when to relax restrictions, evaluating the effectiveness of measures taken and calibrating epidemiological models. | And yet, Mr. Mogstad argued, tracking the infection rate in the population is essential to track the evolution of the virus, including asymptomatic cases, and how it affects people of different races and income levels. That is critical to deciding when to relax restrictions, evaluating the effectiveness of measures taken and calibrating epidemiological models. |
| Figuring out this rate of infection is not that costly. “It’s not about how many you test — it is about who you test,” Mr. Mogstad said, adding that 5,000 tests could do the trick. | Figuring out this rate of infection is not that costly. “It’s not about how many you test — it is about who you test,” Mr. Mogstad said, adding that 5,000 tests could do the trick. |
| The economists’ technique could find other applications. Norway’s statistical agency is planning to use it to improve the response rates to surveys about people’s reaction to the virus and their engagement in social distancing, especially among the young and old. | The economists’ technique could find other applications. Norway’s statistical agency is planning to use it to improve the response rates to surveys about people’s reaction to the virus and their engagement in social distancing, especially among the young and old. |
| The University of Chicago is raising funds to roll out three sets of antibody tests using the incentive technique — one on a nationwide sample and two on samples in Chicago, one of people living below the poverty line, and another of people living above the poverty line. The idea is to provide a proof of concept so the technique can be put into broader use. It could apply equally to antibody tests, which determine which people have been infected, and RNA tests to determine which people are currently infected. | The University of Chicago is raising funds to roll out three sets of antibody tests using the incentive technique — one on a nationwide sample and two on samples in Chicago, one of people living below the poverty line, and another of people living above the poverty line. The idea is to provide a proof of concept so the technique can be put into broader use. It could apply equally to antibody tests, which determine which people have been infected, and RNA tests to determine which people are currently infected. |
| There are other challenges to understand the spread of the coronavirus. Notably, tests are far from perfect. In particular, there are not yet good antibody tests that can faithfully pinpoint people who have been infected with a specific strain of coronavirus. Even when one is developed, tests will have to be deployed across a range of populations and over time, to understand the evolution of the virus and its distribution. | There are other challenges to understand the spread of the coronavirus. Notably, tests are far from perfect. In particular, there are not yet good antibody tests that can faithfully pinpoint people who have been infected with a specific strain of coronavirus. Even when one is developed, tests will have to be deployed across a range of populations and over time, to understand the evolution of the virus and its distribution. |
| And yet the urgency to figure out the reach of the virus is increasing as it spreads. As Mr. Suchard pointed out, individual tracing of the virus can be useful in closed communities or places where it is less common, but in some cities where the virus has become prevalent, “we need population-based sampling” to save lives. | And yet the urgency to figure out the reach of the virus is increasing as it spreads. As Mr. Suchard pointed out, individual tracing of the virus can be useful in closed communities or places where it is less common, but in some cities where the virus has become prevalent, “we need population-based sampling” to save lives. |