The coronavirus pandemic in five powerful charts

A worker disinfects a mosque in Istanbul as part of city-wide efforts to contain the spread of COVID-19. Credit: Chris McGrath/Getty

From papers published to carbon emissions to confirmed cases, these data reveal an unprecedented viral outbreak and its impacts around the world.

How is the coronavirus spreading around the world?

The coronavirus emerged in Wuhan, a city of 11 million people in China's Hubei province, in late 2019. Cases of the disease it causes, COVID-19, grew by several thousand per day in China in late January and early February, the peak of the epidemic there.

The number of infections appearing each day has since plummeted in China, owing in large part to containment efforts, but the outbreak is now a global pandemic. Large outbreaks in South Korea, Iran, Italy and elsewhere have propelled a spike in international cases across more than 150 countries.

Source: World Health Organization

The total number of confirmed cases outside China has now eclipsed those inside the country, and on 13 March, the World Health Organization's director-general Tedros Adhanom Ghebreyesus, said Europe had become the epicentre of the pandemic.

How does COVID-19 compare to other diseases?

Current estimates of COVID-19’s case fatality rate — a measure of the proportion of infected people who eventually die — suggest that the coronavirus is less deadly than the pathogens behind other large-scale outbreaks, such as of SARS (severe acute respiratory syndrome), MERS (Middle East respiratory syndrome) and Ebola.

But the infection also seems to spread more easily than other diseases, including seasonal influenza. Calculations of the virus’s basic reproduction number, or R0 — the number of people on average one infected person will pass the virus to — suggest a range of 2–2.5.

 

Like the case fatality rate, R0 is an estimate that can vary considerably by location, with age group, and over time, and that is likely to be revised. It is calculated using models that take into account how long an infected person remains contagious, the likelihood of them infecting contacts and how often they come into contact with other people.

How fast are researchers publishing new coronavirus research?

The outbreak has prompted an explosion of research on the coronavirus and the disease that it causes. To get an estimate of the scale of research activity, Nature searched for studies using the terms ‘novel coronavirus’, ‘ncov’, ‘COVID-19’ and ‘SARS-CoV-2’ on the bioRxiv, medRxiv, ChemRxiv and ChinaXiv servers, as well as compiling publications listed by the WHO, and on Google Scholar. As of 12 March there had been around 900 papers, preprints and preliminary reports related to coronavirus.

Coronavirus research: Cumulative articles and preprints published.

 

The research covers a range of subjects, including the structure of the virus; how it spreads in different communities; clinical features of the disease; potential drug targets; how effective quarantine measures are; and the psychological effects of the outbreak on health workers. At least 20 of the preprints that were shared early in the outbreak have since been published in peer-reviewed journals.

Researchers have also shared genomic data on the virus using online platforms such as GISAID and GenBank, and several clinical trials are under way for potential vaccines or treatments. Nature’s analysis does not include these reports or data. Neither does it include studies published in languages other than English, for example in Chinese-language journals. It is therefore likely to underestimate the total body of work on the coronavirus so far.

How have travel restrictions affected carbon emissions and air quality?

China’s efforts to control the outbreak seem to have curbed energy consumption — and air pollution. Satellite data collected by NASA and the European Space Agency show a sharp reduction in atmospheric levels of nitrogen dioxide (NO2), which is produced during fossil fuel combustion, across the country.

Source: NASA Earth Observatory

Each year, industrial activity typically drops off as businesses and factories close for celebrations of the lunar New Year, which this year began on 25 January. This usually causes a brief dip in levels of NO2. “Normally, the pollution levels pick back up after 7–10 days, but that has not happened this year,” says Fei Liu, an atmospheric scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. A preliminary analysis suggests that NO2pollution after the lunar New Year was around 10–30% lower this year than during the same period in previous years. A similar trend of declining NO2pollution has also been documented in northern Italy — where cities remain on lockdown — using data from the European Space Agency's Sentinel-5P satellite.

Ongoing efforts to contain the coronavirus have suppressed China’s industrial activity by 15–40%, according to an analysis by the Centre for Research on Energy and Clean Air in Helsinki. Coal consumption hit a four-year low in February, and oil refining fell by more than one-third. Overall, the centre’s analysis suggests that China’s carbon emissions have dropped by more than 25% as a result of the ongoing efforts to contain the coronavirus.

How does the current pandemic compare to the 2003 SARS outbreak?

The COVID-19 coronavirus has, from the beginning, drawn comparisons to the 2002–03 outbreak of SARS. Both originated in China before spreading around the world. Both were identified as new coronaviruses, deadlier than the handful of related viruses that cause common colds. The SARS coronavirus was found to have jumped to people from civet cats that had picked it up from bats. The COVID-19 virus, called SARS-CoV-2, is also thought to have come from bats, either directly or through an as-yet unidentified mammal. Both viruses caused chaos and economic disaster. But the two outbreaks have progressed very differently, especially in the speed and extent of spread.

CORONAVIRUS TIMELINE: Comparison of the SARS and new coronavirus outbreak over time.

 

The SARS outbreak went on for three months before being identified as a distinct disease. Then, for nearly two more months, it was a disease in search of a pathogen: the identification and genomic sequencing of the virus itself largely came from researchers outside China.

By contrast, three weeks after the first known case of the disease now known as COVID-19, China had notified the WHO of a spike in cases of a pneumonia-like disease. Two weeks after that, the coronavirus had been isolated, genetically sequenced, and a diagnostic test developed, giving China the tools it needed to launch one of the greatest infectious-disease containment efforts the world has ever seen.

The COVID-19 virus, although not as lethal as SARS, has proved much more pervasive. It took less than two months from the discovery of the first infection for the number of confirmed cases to pass the total that SARS reached over several months. And in three months, COVID-19 has killed more than five times as many people as SARS.

doi: 10.1038/d41586-020-00758-2

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When will the coronavirus outbreak peak?

Officials want to know but predictions vary wildly, from now to after hundreds of millions of people are infected.

People seen lining up outside a pharmacy store in China.

Officials want to know roughly when the outbreak will peak so they can prepare hospitals. Credit: SOPA Images/LightRocket/Getty

Coronavirus infections in China continue to swell by thousands a day, prompting epidemiologists to estimate when the outbreak will peak. Some suggest the climax, when the number of new infections in a single day reaches its highest point, will happen any time now. Others say that it is months away and that the virus will infect millions — or in one estimate hundreds of millions — of people first.

Public health officials want to know roughly when the peak will be — and how many will be infected — so that they can prepare hospitals and know when it will be safe to lift travel restrictions. Wuhan, the city at the centre of the epidemic, and several other nearby cities have been on lockdown since late January.

Although peak predictions can be illuminating, some researchers warn that accuracy is difficult to achieve, especially when the data used in models are incomplete. “If you revise your predictions every week to say that the outbreak will peak in a week or two, eventually you will be correct,” says Brian Labus, who works on disease surveillance at the University of Nevada, Las Vegas.

Optimistic scenario

On 11 February, Zhong Nanshan, a prominent Chinese physician leading a panel of experts helping to control the outbreak, said that the coronavirus will possibly peak by the end of February. Zhong, who is famous for discovering the SARS virus, said the situation had improved with government control measures, such as travel restrictions and extended holidays, although he admitted that it was still a “difficult period” for Wuhan.

So far, more than 70,000 people have been confirmed to have the disease, now known as COVID-19, in China. But many scientists assume that the number of cases is higher than is being reported. They suspect that China has too few diagnostic tests and health-care workers to confirm all cases. Some scientists also wonder whether Zhong is just trying to reassure people, given the outbreak’s impact on the economy and society.

At least one model aligns with Zhong’s estimate. Researchers at the London School of Hygiene and Tropical Medicine predict that the peak could occur anytime now. Sebastian Funk, a statistician who models infectious diseases and who coauthored the analysis, says the prediction is based on an estimate that one infected person in Wuhan was, on average, infecting between 1.5 and 4.5 others — a measure known as the virus’s effective reproduction number, or R — before the travel restrictions were introduced on 23 January. Funk estimates that at the peak around a million people, about 10% of Wuhan's population, will be infected.

Funk posted the analysis, which has not been peer-reviewed, on his institute’s website on 12 February. But he says that since it was done, a decline in the number of new cases and deaths in Wuhan suggests that infections might have already peaked. (More than 14,000 new cases were reported on 13 February, but the bump was due to authorities changing the way cases are diagnosed and not a true spike).

Worst case

Some researchers find such predictions overly optimistic. People in most Chinese cities started returning to work last week after an extended public-holiday period — opening up the possibility of new chains of transmission, says Hiroshi Nishiura, an epidemiologist at Hokkaido University in Sapporo, Japan.

Nishiura says he has used a model that estimates that the outbreak will peak sometime between late March and late May. At this point, he says, up to 2.3 million cases will be diagnosed in a single day. In total, he estimates that between 550 million and 650 million people across China will be infected, roughly 40% of the country’s population. Nishiura says that about half of those people will show symptoms.

Nishiura says he has submitted a paper describing the model and its prediction to the preprint server medRxiv. To make such a prediction, he says that his team considered the transmission potential inherent to the new virus — the basic reproduction number known as R0, which is related to R, although it assumes that everyone in the population is susceptible to infection. The team estimates the R0 is between 1.5 and 2.

He says that his model presents a relatively simplistic outlook because it assumes that everyone in the population is susceptible. It also reflects the view that many people who have been infected are asymptomatic or not unwell enough to seek medical treatment. If that is the case, the current number of reported cases massively underestimates the number of people infected, he says.

Gabriel Leung, an epidemiologist at the University of Hong Kong, says that Nishiura’s estimates are feasible. The community has no immunity to SARS-CoV-2, the virus that causes COVID-19 so “it will sweep through”, he says.

Leung says that while those estimates sound extreme, it’s still not clear how deadly the virus is. The latest calculation of the fatality rate, in a paper published by Zhong on 9 February, suggests that there are about 1.36 deaths per hundred cases. But that number is probably too high because the authors did not consider less severe cases. (Outside China, two deaths have been reported in 500 cases.)

Quarantine measures

Leung says it's also unclear what effect, if any, that control measures, such as travel bans and quarantining people, have had on the timing and severity of the peak. Nishiura and Funk say their models excluded these measures because their efficacy is uncertain.

Many scientists say that control measures might not, ultimately, decrease the number of people infected. But they could extend the time taken for the epidemic to peak, by slowing transmission, says Leung.

Reducing the number of people who get infected at the peak is important, says Leung. If everyone gets sick at the same time, “the entire society grinds to a halt,” he says. “Health services will be overwhelmed and people will die.”

 

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