The outbreak of a new virus that began in the Chinese city of Wuhan last month appears to be far from over. Today, Chinese health authorities reported that over 130 new pneumonia cases caused by the virus were identified over the weekend, bringing the total in China alone to 201, including three outside Wuhan. There has also been a third death from the infection, and South Korea now has reported a case as well—the third country outside China to do so.
Meanwhile, the pattern of spread makes it increasingly unlikely that the virus does not transmit between people, some experts say. "Uncertainty and gaps remain, but it’s clear that there is some level of person-to-person transmission,” Jeremy Farrar, head of the Wellcome Trust in London, said in a statement today.
"The sudden spike in cases is disconcerting, but not entirely unexpected," says Adam Kamradt-Scott, an infectious diseases specialist at the University of Sydney. As more people learn about the disease, more will go to doctors, Kamradt-Scott says, even with mild symptoms, whereas previously they might have just stayed home. And doctors are now on the lookout for the new disease. "The result is that you see a sudden surge in cases," he says. But “if we continue to see this trend continue over the next week where there are 50 to 100 new cases every day, then that would be cause for further concern."
The outbreak began in mid-December in Wuhan, a major city and travel hub in central China. Many of the initial patients had worked or shopped at the city's Huanan Seafood Wholesale Market, at which vendors also sold live birds and other animals, suggesting the infection was jumping from animals to humans. By 8 January, Chinese scientists had identified a new member of the coronavirus family as the likely culprit. They soon sequenced and released its genome, allowing scientists worldwide to create diagnostic tests.
A week ago, new cases seemed to be tapering off—but then more patients started appearing. Early on Monday local time, the Wuhan Municipal Health Commission reported identifying 59 new cases on 18 January and an additional 77 on the 19th. One patient died on Saturday, bringing the number of deaths to three. Nine remain critically ill. Authorities separately confirmed that two patients had been identified in Beijing and one in Shenzhen, a major city bordering Hong Kong. Before the new case in South Korea, two travelers from Wuhan were found to be infected in Thailand and one in Japan.
Health authorities worry about further spread of the virus as several hundred million Chinese are expected to travel domestically to visit relatives during the weeklong Chinese New Year festivities, which start on 25 January. Millions are also expected to travel internationally for vacation, with Thailand and Japan being top destinations.
Scientists are still puzzling over whether other markets in Wuhan are involved, and whether the virus can pass from person to person. One of the patients in Thailand reported she had not visited the Huanan market, but she had been to other wet markets. The patient that turned up in Japan after traveling to Wuhan reportedly also said he had never been to the Huanan market.
Other coronaviruses—including the ones that cause severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS)—do spread between people. And many scientists say human-to-human transmission of the Wuhan virus cannot be ruled out. But Wuhan health authorities have said they have found no evidence of it so far. They have tracked 817 close contacts of patients, of whom 727 were cleared of illness; the remaining 90 are still under observation. Wuhan authorities have also reported that no health care workers tending to coronavirus patients have become ill, a common occurrence when a new virus with the ability to spread between people emerges. (It is not clear if authorities have tested patient contacts for antibodies to the virus, which would be a sign that they were infected at some point but recovered.)
The sudden spike in cases is disconcerting, but not entirely unexpected.
“The mode(s) of transmission has not yet been determined and human to human transmission is always a concern when patients have respiratory symptoms, this requires further investigation,” a WHO spokesperson writes in an email to Science.
The virus does not currently appear to be especially virulent and in the majority of cases has caused mild illness. "This means we need to continue to closely monitor the situation, but not panic," says Kamradt-Scott.
Meanwhile, on Saturday, the Chinese Center for Disease Control and Prevention (China CDC) posted information for the public about the new disease with colorful, cartoonish graphics showing coronaviruses and bats, apparently in an attempt to quash misinformation on Weibo, a Twitter-like social media site. The China CDC website emphasizes that the disease is not SARS—whose emergence in late 2002 caused a global crisis that many Chinese remember well—and urges people to "not believe five big rumors about the Wuhan viral pneumonia." Those include claims that the Wuhan pneumonia is caused by a new SARS virus; that the SARS virus is still being found in bats; and that the Wuhan pneumonia may have been affecting people for a long time.