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As the death toll from COVID-19 — the disease caused by the novel coronavirus — rises worldwide, the chart below shows that the count has so far risen at different rates in some of the worst-affected countries. The chart will update daily to reflect the data from the previous calendar day.
The chart plots the number of deaths on a logarithmic scale, which makes the difference between 10 and 100 take up the same height on the chart as the difference between 100 and 1,000. This turns the steeply rising curves of rapidly growing epidemics into straighter lines — making it easier to compare their trajectories. The lines for each country have also been aligned so that “day zero” is when a country reported 10 deaths. (Days are defined in Coordinated Universal Time, which is four hours ahead of US Eastern Time.)
If a line flattens out — like China’s — it suggests that the epidemic is starting to come under control. There were also differences in the slope of the lines at the start, with the death tolls in the US and particularly in South Korea rising more slowly than in most of the other countries shown.
In the early stages of the US outbreak, experts warned that these trajectories could change. “I think it’s too early in the course in most countries to draw conclusive insights from the mortality trajectories,” Thomas Tsai, a health policy researcher at Brigham and Women’s Hospital in Boston, told BuzzFeed News by email on March 17, or day 13 for the US on the chart above. “Until more data are available, relying on social distancing to prevent transmission appears to be the most effective public health strategy.”
Since that time, the US trajectory has steepened, and is now running parallel to those of European countries. There are also signs that Italy’s curve has started to flatten, probably as a consequence of the nationwide lockdown ordered on March 9, which restricted travel to work and emergencies.
Two leading theories of the differences in the initial death toll trajectories have to do with the ages of people who were infected and the fact that the US health care system — for all its failings and inefficiencies — has more critical care beds for people who are seriously ill.
But there is no room for complacency: If the number of new cases builds up too quickly, even US intensive care units will be unable to cope. If there are not enough critical care beds to handle the demand, said Vikas Saini, president of the Lown Institute, a health care think tank in Brookline, Massachusetts, “the best critical care in the world is not going to move the needle.”
As the pandemic has continued, the trajectories for total confirmed cases in different countries have diverged.
On this chart, day zero for each country is set at when the confirmed case count exceeded 500. As the chart shows, the early growth in confirmed cases was similar from country to country, indicating that the same basic pattern of exponential growth happened in each of these countries after the virus took hold. But the US trajectory for cases steepened from about day 10 after states, led by New York, started significantly ramping up testing.
Cases are still being undercounted, and the extent of the undercount varies widely from country to country.
The clear standout on this chart is the line for South Korea, which from about day 10 started to flatten out. Experts agree that the country’s response to the epidemic has been a model for others to follow.
Right from the start, South Korea rolled out widespread testing, tracked the contacts of known cases, and enforced strict quarantines on people who tested positive for the virus. As a result, South Korea has for now limited its outbreak without having to tell badly affected regions to shelter in place or put the entire nation on lockdown.
Experts also have a good idea of why the death toll, shown in the first chart, has been rising slowly in South Korea. Its largest cluster of cases occurred in the congregation of the Shincheonji Church of Jesus in Daegu, where an infected woman known as “patient 31” attended two services in February.
Shincheonji churchgoers were mostly young. That’s important, because a study of more than 72,000 cases from China has shown that the virus is more fatal among the elderly. Just 0.2% of Chinese patients in their twenties died of COVID-19, compared to 8% of those in their seventies and almost 15% of those in their eighties.
In a Medium post published March 13, economist Andreas Backhaus of the Centre for European Policy Studies in Brussels compared the age distribution of COVID-19 patients in South Korea and Italy. In South Korea, almost 30% of patients were in their twenties and just 3% in their eighties. In Italy, where there was widespread infection of an older population, less than 4% were in their twenties and more than 19% in their eighties.
But that still leaves the mystery of why the US’s death toll initially grew more slowly than those of other countries. One possibility is that US hospitals are better equipped to provide critical care than those in many other nations.
Comparisons among the health care systems of different countries, which rank the US poorly compared to leading European nations, typically measure their efficiency at delivering all kinds of care. The US system is notoriously expensive and access to primary care is patchy. But it excels at providing high-tech, intensive care for severely ill patients.
“US rescue care and acute care is maybe the best in the world,” David Hamer, a specialist in global health and infectious diseases at Boston University, told BuzzFeed News.
This international comparison, posted by the Society of Critical Care Medicine, comes from numbers quoted in three studies published between 2012 and 2020. The more extensive critical care provision in countries like the US and Germany may make them somewhat less vulnerable to getting overwhelmed by caring for people with COVID-19.
But if countries fail to “flatten the curve” of new cases, projections indicate that even the best-equipped health systems will be overwhelmed. That already seems to be happening at hospitals in New York City, which has been hit hard by COVID-19.
The UK is in a particularly precarious position. On March 16, scientists at Imperial College, London, released a modeling study indicating that the British health system would be overwhelmed even if schools and universities closed and everyone older than 70 practiced social distancing. Only “suppression” strategies involving social distancing for the entire population were likely to prevent that happening, the report concluded. After previously rejecting strict curbs on normal activities, Prime Minister Boris Johnson urged everyone to avoid unnecessary social contact, and on March 23, ordered that people should only leave their homes for essential reasons.
As the virus continues to spread, the age distribution of the population in different countries will become an important factor. The charts below show the relative size of key nations’ populations in the most vulnerable elderly groups.
These charts suggest that China’s relatively young population may have limited the number of deaths due to COVID-19. They also explain why Italy is so vulnerable. The US population is a little younger than those of leading European countries, but still has more than 10% of age 70 and over.
In addition to regularly updating the data in the charts, this post will be updated with other information as it becomes available.