In just six months, nearly 8 million people worldwide have been stricken with confirmed cases of Covid-19, and at least 434,000 have died. But those deaths have not been distributed evenly; among the most vulnerable are people with underlying health conditions, such as diabetes and diseases that affect the heart and lungs. According to a new modeling study, roughly 1.7 billion people around the world — 22 percent of the global population — fall into that category.
That estimate, published today in The Lancet Global Health, excluded healthy older individuals without underlying health conditions, a group also known to be at risk because of their age. It also did not take into account risk factors like poverty and obesity, which can influence a person’s susceptibility to disease and access to treatment.
But such data could help health officials focus containment efforts on people vulnerable to the virus’s most dangerous effects and, perhaps, eventually prioritize them for vaccination, said Andrew Clark of the London School of Hygiene and Tropical Medicine, the study’s first author. Since the early days of the pandemic, researchers have known that chronic conditions can exacerbate disease. Now, there’s a better “understanding of the numbers involved,” Dr. Clark said.
The researchers compiled 11 categories of underlying conditions that may raise the risk of severe Covid-19 — a form of symptomatic disease that warrants hospitalization — using information from the World Health Organization and health agencies in the United States and Britain.
The list includes patients who regularly take immunosuppressive drugs, such as those with autoimmune disorders, or are undergoing immunity-weakening treatments like chemotherapy.
Not all of the conditions have been well studied in the context of Covid-19, cautioned Dr. Lona Mody, an epidemiologist at the University of Michigan who was not involved in the study. Little is known, for instance, about the risks for people with H.I.V., listed in the study as a potential complicating factor.
And Nina Schwalbe, a public health researcher at Columbia University and the author of a commentary accompanying the new study, reiterated that anyone infected with the coronavirus is at some risk of Covid-19, its severity dependent on a bevy of health-related factors.
The researchers mined data from the Global Burden of Disease Study, a comprehensive worldwide epidemiological survey last updated in 2017, to identify the number of individuals worldwide with at least one of these high-risk conditions. Nearly 200 countries were included in the final tally, with some, such as those in Europe, harder hit than others. In total, the analysis found, more than one-fifth of the world’s population may be at increased risk of more severe disease.
But increased risk is not equivalent to high risk, a category that refers to only a small subset of patients, Dr. Clark emphasized. Even if they are infected with the coronavirus, “not everyone with a condition will progress to a hospital,” he said.
The study also estimated that about 4 percent of the world’s population, around 349 million people, would require hospitalization if they became infected. That number includes patients without underlying medical conditions, such as healthy, older adults; and the risk of hospitalization increases with age.
Many of the other factors that can send a patient on a path toward severe disease are still unclear. Several are likely inextricably linked to so-called social determinants of health — conditions like poverty and health care access, which are not measured by the Global Burden of Disease Study, said Alex Ortega, an epidemiologist at Drexel University who was not involved in the study. The research also did not look at obesity, which has emerged as another prominent complicating risk factor. (A similar but separate analysis that included severe obesity as a complicating factor, published today by the Kaiser Family Foundation, found that nearly one-quarter of American adult workers are at risk of severe Covid-19.)
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Updated June 12, 2020
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Does asymptomatic transmission of Covid-19 happen?
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.
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What’s the risk of catching coronavirus from a surface?
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.
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How does blood type influence coronavirus?
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.
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How many people have lost their jobs due to coronavirus in the U.S.?
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.
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Will protests set off a second viral wave of coronavirus?
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.
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How do we start exercising again without hurting ourselves after months of lockdown?
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.
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My state is reopening. Is it safe to go out?
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.
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What are the symptoms of coronavirus?
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.
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How can I protect myself while flying?
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.)
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Should I wear a mask?
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.
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What should I do if I feel sick?
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.
Moreover, the underlying conditions that increase the severity of Covid-19 in one country won’t necessarily do so in another, said Aditya Khanna, an epidemiologist at the University of Chicago who was not involved in the study. The local environment and people’s social habits also factor into health — and studies that apply the same metrics across different parts of the world “need to be taken with a grain of salt,” Dr. Khanna said.
Still, the study was greeted as a step in the right direction. “This begins to move us past the one-size-fits-all approach,” Ms. Schwalbe said. “The more precision we can get at who’s at risk of hospitalization, the better we can work with those people and tailor our response appropriately.”
