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Why Are Some People So Much More Infectious Than Others? Why Are Some People So Much More Infectious Than Others?
(1 day later)
As the coronavirus tears through the country, scientists are asking: Are some people more infectious than others? Are there superspreaders, people who seem to just spew out virus, making them especially likely to infect others?As the coronavirus tears through the country, scientists are asking: Are some people more infectious than others? Are there superspreaders, people who seem to just spew out virus, making them especially likely to infect others?
It seems that the answer is yes. There do seem to be superspreaders, a loosely defined term for people who infect a disproportionate number of others, whether as a consequence of genetics, social habits or simply being in the wrong place at the wrong time.It seems that the answer is yes. There do seem to be superspreaders, a loosely defined term for people who infect a disproportionate number of others, whether as a consequence of genetics, social habits or simply being in the wrong place at the wrong time.
But those virus carriers at the heart of what are being called superspreading events can drive and have driven epidemics, researchers say, making it crucial to figure out ways to identify spreading events or to prevent situations, like crowded rooms, where superspreading can occur.But those virus carriers at the heart of what are being called superspreading events can drive and have driven epidemics, researchers say, making it crucial to figure out ways to identify spreading events or to prevent situations, like crowded rooms, where superspreading can occur.
Just as important are those at the other end of the spectrum — people who are infected but unlikely to spread the infection.Just as important are those at the other end of the spectrum — people who are infected but unlikely to spread the infection.
Distinguishing between those who are more infectious and those less infectious could make an enormous difference in the ease and speed with which an outbreak is contained, said Jon Zelner, an epidemiologist at the University of Michigan. If the infected person is a superspreader, contact tracing is especially important. But if the infected person is the opposite of a superspreader, someone who for whatever reason does not transmit the virus, contact tracing can be a wasted effort.Distinguishing between those who are more infectious and those less infectious could make an enormous difference in the ease and speed with which an outbreak is contained, said Jon Zelner, an epidemiologist at the University of Michigan. If the infected person is a superspreader, contact tracing is especially important. But if the infected person is the opposite of a superspreader, someone who for whatever reason does not transmit the virus, contact tracing can be a wasted effort.
“The tricky part is that we don’t necessarily know who those people are,” Dr. Zelner said.“The tricky part is that we don’t necessarily know who those people are,” Dr. Zelner said.
Two factors are at play, said Martina Morris, emeritus professor of statistics and sociology at the University of Washington.Two factors are at play, said Martina Morris, emeritus professor of statistics and sociology at the University of Washington.
“There has to be a link between people in order to transmit an infection,” she said. But, she added, a link “is necessary but not sufficient.” The second factor is how infectious a person is. “We almost never have independent data on those two things,” Dr. Morris said.“There has to be a link between people in order to transmit an infection,” she said. But, she added, a link “is necessary but not sufficient.” The second factor is how infectious a person is. “We almost never have independent data on those two things,” Dr. Morris said.
She pointed out that it can be easy to misattribute multiple infections to an individual — possibly exposing the person to public attack — when the spread has nothing to do with the person’s infectiousness.She pointed out that it can be easy to misattribute multiple infections to an individual — possibly exposing the person to public attack — when the spread has nothing to do with the person’s infectiousness.
“If you are the first person in a crowded room to get infected and if this is an easily spread disease, you will look like a superspreader,” she said. “Anyone in that room could have had the same impact. You were just the first in line.”“If you are the first person in a crowded room to get infected and if this is an easily spread disease, you will look like a superspreader,” she said. “Anyone in that room could have had the same impact. You were just the first in line.”
Yet there do seem to be situations in which a few individuals spark large outbreaks. With Covid-19, it is not yet known whether those highly infectious people include individuals with silent infections who do not realize they are sick, said Dr. Thomas Frieden, former director of the Centers for Disease Control and Prevention and chief executive at Resolve to Save Lives, an initiative of Vital Strategies. More likely, he adds, superspreading events may involve people with symptoms that linger but who are not sick enough to stay home.Yet there do seem to be situations in which a few individuals spark large outbreaks. With Covid-19, it is not yet known whether those highly infectious people include individuals with silent infections who do not realize they are sick, said Dr. Thomas Frieden, former director of the Centers for Disease Control and Prevention and chief executive at Resolve to Save Lives, an initiative of Vital Strategies. More likely, he adds, superspreading events may involve people with symptoms that linger but who are not sick enough to stay home.
Or they could involve infected people who shed an unusual amount of virus — a poorly studied factor that might be due to variations in the amount of virus in the aerosol droplets from a patient’s cough or the amount of infectious virus in feces, for example.Or they could involve infected people who shed an unusual amount of virus — a poorly studied factor that might be due to variations in the amount of virus in the aerosol droplets from a patient’s cough or the amount of infectious virus in feces, for example.
No matter what the cause, public health measures, like avoiding crowds, and what Dr. Frieden calls cough hygiene, can prevent a superspreading event, he said.No matter what the cause, public health measures, like avoiding crowds, and what Dr. Frieden calls cough hygiene, can prevent a superspreading event, he said.
Medical history is replete with stories of superspreading in outbreaks of parasitic disease, tuberculosis, measles and other illness.Medical history is replete with stories of superspreading in outbreaks of parasitic disease, tuberculosis, measles and other illness.
There is Mary Mallon, a cook better known as Typhoid Mary, who spread typhoid fever to more than 50 people in the early years of the twentieth century. She herself was not ill but was asymptomatic — silently infected with typhoid.There is Mary Mallon, a cook better known as Typhoid Mary, who spread typhoid fever to more than 50 people in the early years of the twentieth century. She herself was not ill but was asymptomatic — silently infected with typhoid.
Superspreading also played important roles in outbreaks of two other coronaviruses, SARS and MERS.Superspreading also played important roles in outbreaks of two other coronaviruses, SARS and MERS.
“The MERS-CoV outbreak in South Korea was driven primarily by three infected individuals, and approximately 75 percent of cases can be traced back to three superspreaders who have each infected a disproportionately high number of contacts,” wrote George F. Gao, an immunologist and virologist at the Chinese Centers for Disease Control and Prevention in Beijing, in a recent paper.“The MERS-CoV outbreak in South Korea was driven primarily by three infected individuals, and approximately 75 percent of cases can be traced back to three superspreaders who have each infected a disproportionately high number of contacts,” wrote George F. Gao, an immunologist and virologist at the Chinese Centers for Disease Control and Prevention in Beijing, in a recent paper.
The outbreak in South Korea began in 2015 when a 68-year-old man became infected with MERS during travel to the Middle East. He returned to South Korea where he directly infected 29 people, two of whom infected 106 people. The total number of cases in South Korea at that time was 166 — that superspreading event accounted for most of the outbreak.The outbreak in South Korea began in 2015 when a 68-year-old man became infected with MERS during travel to the Middle East. He returned to South Korea where he directly infected 29 people, two of whom infected 106 people. The total number of cases in South Korea at that time was 166 — that superspreading event accounted for most of the outbreak.
In 2003 during the SARS outbreak, the first patient in Hong Kong appears to have infected at least 125 others. Other superspreading events involved 180 people in a housing complex in Hong Kong and another 22 people on a jet from Hong Kong to Beijing.In 2003 during the SARS outbreak, the first patient in Hong Kong appears to have infected at least 125 others. Other superspreading events involved 180 people in a housing complex in Hong Kong and another 22 people on a jet from Hong Kong to Beijing.
In the Ebola outbreak in Africa between 2014 and 2016, 61 percent of infections were traced to just 3 percent of infected people.In the Ebola outbreak in Africa between 2014 and 2016, 61 percent of infections were traced to just 3 percent of infected people.
Superspreading also appears to have driven outbreaks of the new coronavirus.Superspreading also appears to have driven outbreaks of the new coronavirus.
One event occurred at the end of February when 175 Biogen executives gathered for a conference at the Boston Marriott Long Wharf Hotel. At least one was infected with the coronavirus. Two weeks later, seventy five percent of the 108 Massachusetts residents infected with the virus were associated with Biogen. The infections rippled out from there, to other states and other Massachusetts residents.One event occurred at the end of February when 175 Biogen executives gathered for a conference at the Boston Marriott Long Wharf Hotel. At least one was infected with the coronavirus. Two weeks later, seventy five percent of the 108 Massachusetts residents infected with the virus were associated with Biogen. The infections rippled out from there, to other states and other Massachusetts residents.
“Why at that conference?” asked Dr. Eric Topol, director of the Scripps research translational institute in San Diego. “At the time there were so many conferences — it was before social distancing. Something was going on there.”“Why at that conference?” asked Dr. Eric Topol, director of the Scripps research translational institute in San Diego. “At the time there were so many conferences — it was before social distancing. Something was going on there.”
Then there was the March 12 birthday party in Westport, Conn. About 50 people attended. Half ended up infected. The cluster of cases expanded so fast health officials gave up contact tracing.Then there was the March 12 birthday party in Westport, Conn. About 50 people attended. Half ended up infected. The cluster of cases expanded so fast health officials gave up contact tracing.
At a funeral on Feb. 29 in Albany, Ga., someone unwittingly spread the virus among the 200 mourners. At Illinois’s current hot spot, the Cook County jail, at least 400 are known to be infected.At a funeral on Feb. 29 in Albany, Ga., someone unwittingly spread the virus among the 200 mourners. At Illinois’s current hot spot, the Cook County jail, at least 400 are known to be infected.
At the other end of the bell curve of infectiousness are infected people who do not seem to infect others. During the MERS outbreak in South Korea, 89 percent of patients did not appear to transmit the disease.At the other end of the bell curve of infectiousness are infected people who do not seem to infect others. During the MERS outbreak in South Korea, 89 percent of patients did not appear to transmit the disease.
Updated June 12, 2020 Updated June 16, 2020
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.
Mass protests against police brutality that have brought thousands of people onto the streets in cities across America are raising the specter of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases. While many political leaders affirmed the right of protesters to express themselves, they urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus. Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open air settings could mitigate the risk of transmission.Mass protests against police brutality that have brought thousands of people onto the streets in cities across America are raising the specter of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases. While many political leaders affirmed the right of protesters to express themselves, they urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus. Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open air settings could mitigate the risk of transmission.
Exercise researchers and physicians have some blunt advice for those of us aiming to return to regular exercise now: Start slowly and then rev up your workouts, also slowly. American adults tended to be about 12 percent less active after the stay-at-home mandates began in March than they were in January. But there are steps you can take to ease your way back into regular exercise safely. First, “start at no more than 50 percent of the exercise you were doing before Covid,” says Dr. Monica Rho, the chief of musculoskeletal medicine at the Shirley Ryan AbilityLab in Chicago. Thread in some preparatory squats, too, she advises. “When you haven’t been exercising, you lose muscle mass.” Expect some muscle twinges after these preliminary, post-lockdown sessions, especially a day or two later. But sudden or increasing pain during exercise is a clarion call to stop and return home.
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.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.)
Taking one’s temperature to look for signs of fever is not as easy as it sounds, as “normal” temperature numbers can vary, but generally, keep an eye out for a temperature of 100.5 degrees Fahrenheit or higher. If you don’t have a thermometer (they can be pricey these days), there are other ways to figure out if you have a fever, or are at risk of Covid-19 complications.Taking one’s temperature to look for signs of fever is not as easy as it sounds, as “normal” temperature numbers can vary, but generally, keep an eye out for a temperature of 100.5 degrees Fahrenheit or higher. If you don’t have a thermometer (they can be pricey these days), there are other ways to figure out if you have a fever, or are at risk of Covid-19 complications.
The C.D.C. has recommended that all Americans wear cloth masks if they go out in public. This is a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms. Until now, the C.D.C., like the W.H.O., has advised that ordinary people don’t need to wear masks unless they are sick and coughing. Part of the reason was to preserve medical-grade masks for health care workers who desperately need them at a time when they are in continuously short supply. Masks don’t replace hand washing and social distancing.The C.D.C. has recommended that all Americans wear cloth masks if they go out in public. This is a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms. Until now, the C.D.C., like the W.H.O., has advised that ordinary people don’t need to wear masks unless they are sick and coughing. Part of the reason was to preserve medical-grade masks for health care workers who desperately need them at a time when they are in continuously short supply. Masks don’t replace hand washing and social distancing.
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.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.
In the Covid-19 pandemic, there is a striking example from the far end of uninfectious — a couple in Illinois.In the Covid-19 pandemic, there is a striking example from the far end of uninfectious — a couple in Illinois.
On Jan. 23 the wife, who had returned from a visit to Wuhan — became the first laboratory-confirmed case of Covid-19 in the state. On Jan. 30, her husband was infected. It was the first known person-to person transmission in the United States.On Jan. 23 the wife, who had returned from a visit to Wuhan — became the first laboratory-confirmed case of Covid-19 in the state. On Jan. 30, her husband was infected. It was the first known person-to person transmission in the United States.
Both husband and wife became gravely ill and were hospitalized. Both recovered.Both husband and wife became gravely ill and were hospitalized. Both recovered.
State public health officials traced their contacts — 372 people, including 195 health care workers. Not a single one became infected.State public health officials traced their contacts — 372 people, including 195 health care workers. Not a single one became infected.
Dr. Jennifer Layden, chief medical officer for the Chicago Department of Public Health, said the remarkable lack of spread probably arose from several factors. Where were the couple in the course of their infection when they came into contact with those other people? Were they sneezing or coughing? How close were the contacts? Were the people they interacted with simply less susceptible to infections?Dr. Jennifer Layden, chief medical officer for the Chicago Department of Public Health, said the remarkable lack of spread probably arose from several factors. Where were the couple in the course of their infection when they came into contact with those other people? Were they sneezing or coughing? How close were the contacts? Were the people they interacted with simply less susceptible to infections?
As grimly alluring as it is to look for viral superspreaders, there are pitfalls.As grimly alluring as it is to look for viral superspreaders, there are pitfalls.
There is a good chance that a cluster of infections would be attributed to a superspreader when, instead, public health officials missed some transmissions by other people, Dr. Zelner said. And there are social consequences to superspreader stories.There is a good chance that a cluster of infections would be attributed to a superspreader when, instead, public health officials missed some transmissions by other people, Dr. Zelner said. And there are social consequences to superspreader stories.
“The nature of our society right now is that we are very much interested in the catastrophic,” said Samuel K. Roberts, a medical historian at Columbia. “The best way to do that is to have something that looks like a zombie story. It’s a powerful narrative.”“The nature of our society right now is that we are very much interested in the catastrophic,” said Samuel K. Roberts, a medical historian at Columbia. “The best way to do that is to have something that looks like a zombie story. It’s a powerful narrative.”
The general public doesn’t need to know if an outbreak was traced to one person, he said.The general public doesn’t need to know if an outbreak was traced to one person, he said.
“What’s more important is, How do we protect ourselves?” he said. “Finding patient zero is not going to help. It only stokes fear of the other.”“What’s more important is, How do we protect ourselves?” he said. “Finding patient zero is not going to help. It only stokes fear of the other.”
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