![\"A](\"\/\/media.nature.com\/lw800\/magazine-assets\/d41586-020-00434-5\/d41586-020-00434-5_17704106.jpg\")
<\/div>\n<\/div>Researchers want to know how many people with the coronavirus don’t have symptoms.<\/span>Credit: Stringer\/Getty<\/p>\n<\/figcaption><\/figure>\n <\/p>\n <\/p>\n Researchers are concerned that China\u2019s official reports on the number of coronavirus infections have not been including people who have tested positive for the virus but who have no symptoms. They fear the practice is masking the epidemic\u2019s true scale. But public health experts say China is right to prioritize tracking sick patients who are spreading the disease.<\/p>\n Since the early days of the outbreak, the country\u2019s National Health Commission has reported daily infection counts, which infectious-disease researchers outside China have been relying on to model the outbreak\u2019s spread and severity.<\/p>\n Earlier this month, officials from Heilongjiang province in northeast China announced that 13 people who had tested positive for the virus with a lab test but who had no symptoms had been removed from the region\u2019s list of confirmed cases. Officials said that they were following the commission\u2019s guidelines for reporting infections, which state that such people should be classified as \u2018positive cases\u2019 rather than \u2018confirmed cases\u2019. Only confirmed cases are noted in the commission\u2019s official daily reports.<\/p>\n The situation in Heilongjiang has put a spotlight on China\u2019s reporting guidelines. These had already been getting attention after they were updated on 7 February to allow physicians to confirm cases using images from chest scans rather than waiting days for lab tests. The change in diagnostic criteria saw infections in Hubei, the province at the centre of the epidemic, jump by nearly 15,000 cases in a single day last week.<\/p>\n <\/p>\n <\/p>\n <\/p>\n Wu Zunyou, the chief epidemiologist at the Chinese Center for Disease Control and Prevention in Beijing, who helps to implement the guidelines, says that they have always required that positive cases not be counted as confirmed cases. Instead, those who test positive are isolated for 14 days and monitored by health authorities. If they develop symptoms in that period, they are classified as a confirmed case.<\/p>\n Wu says that a positive test doesn\u2019t necessarily mean that a person is infected with the virus. Lab tests typically detect genetic material from the virus in throat or nasal swabs, but in some people the virus might not have entered cells and started replicating, he says. But it\u2019s not clear whether such \u2018carriers\u2019, who test positive for the virus but are not actually infected, exist. \u201cThat is one of the big scientific questions,\u201d he says.<\/p>\n But several infectious-disease researchers outside China who spoke to\u00a0Nature<\/i>\u00a0disagree. A virus usually has to replicate inside a host to reach detectable levels, says Angela Rasmussen, a virologist at Columbia University in New York. If the virus is in a person\u2019s nose but hasn\u2019t infected any cells, then \u201cI\u2019m sceptical that virus in a nasal swab from this type of exposure would be detectable,\u201d she says.<\/p>\n Omitting these cases from official counts gives the impression that the virus is more severe than it really is, says Ian Mackay, a virologist at the University of Queensland in Brisbane. This could mislead other countries that are trying to prepare for the most likely effects of an epidemic of the disease, known as COVID-19, in their population, says Mackay.<\/p>\n <\/p>\n <\/p>\n <\/p>\n Not counting asymptomatic cases also hampers efforts to model the virus to understand its extent and spread, says Michael Mina, an infectious-disease immunologist and epidemiologist at the Harvard T. H. Chan School of Public Health in Boston, Massachusetts. Epidemiologists try to piece together chains of transmission, and they might include people who are infected by have no symptoms, says Mina.<\/p>\n He and other researchers suspect that many more people have been infected than the 74,000-odd cases that have been reported, and that most cases are probably asymptomatic and would be positive if tested.<\/p>\n Tarik Ja\u0161arevi\u0107, spokesman for the World Health Organization in Geneva, Switzerland, said that from a public health point of view, it makes sense for China to focus on recording numbers of patients who have symptoms because those people seem to be the ones transmitting the virus to others.<\/p>\n Mina says that China is probably also prioritizing care for the sick, and maintaining quarantines, rather than measuring the epidemic\u2019s dynamics. From a clinical perspective, the exclusion of asymptomatic patients from case counts is justified, because if a person has no symptoms, they don\u2019t need medical treatment. \u201cIf I put on my medical hat for a moment, I can understand the decision not to count these individuals,\u201d he says.<\/p>\n <\/p>\n <\/p>\n<\/div>\n <\/p>\n <\/p>\n <\/p>\n (\uc6d0\ubb38: \uc5ec\uae30<\/a>\ub97c \ud074\ub9ad\ud558\uc138\uc694~)<\/p>\n <\/p>\n <\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":"Reporting requirements<\/h2>\n
Lost contacts<\/h2>\n