There have been reports that the Wuhan coronavirus may be transmittable whilst asymptomatic. Professor Mark Woolhouse, Professor of Infectious Disease Epidemiology, University of Edinburgh “In my view it is premature to conclude, on the basis of the evidence currently available, that the new virus can be transmitted before symptoms appear. The anecdotal report from China that a single instance of asymptomatic transmission had occurred is based on the history of a single cluster of cases, it is open to alternative interpretations and there is no indication that the publicised information has been confirmed (as it could be for example, by analysis of the viral genome sequences from the patients involved). This is flimsy evidence on which to base such an important conclusion. If the National Health Commission of China have stronger evidence then it is important that they share it promptly. “In any case, this is a new virus and we are still learning about it, including how and when transmission can occur. Further, robust research on this point is urgently needed. That is because the question is crucially important. In the absence of any treatment or vaccine our main hope of controlling the epidemic is the rapid identification of cases and the immediate prevention of onward transmission through patient isolation and infection control. The efficacy of those interventions would be compromised if significant levels of transmission occurred before symptoms appeared and the patient reported to a health care facility.” Professor Bill Keevil, Professor of Environmental Healthcare, University of Southampton, said: “Since I cited the Lancaster University study suggesting an Ro of 3.6-3.8, there have been several other published estimates, one from China suggesting 3.8 and the MRC Unit in London’s very recent estimate of 2.6 (but uncertainty range 1.5-3.5). These are worryingly high numbers and support the rapidly increasingly numbers of infections. It is essential to maintain genome sequencing to understand how and how fast the virus is mutating and whether this points to development of more lethal forms. As I stressed, good containment and hygiene measures are essential, especially hand hygiene which is a principal transmission route – probably also for symptomless transmission. Wearing face masks may give a false sense of security if aerosol coughs contain submicron particles. Our paper on the related human coronavirus 229E showed it survived over 4 days on common materials such as plastics, ceramics, glass and stainless steel, making regular surface cleaning and hand hygiene paramount. Several authors have advocated everyone wearing gloves, as we do in microbiology labs, carefully removing them and then washing hands.” Professor David Heymann, Professor of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, said: “Virus transmission occurs when there is a high enough level of virus in the blood and body secretions of an infected person to another. Some infections can be passed from one human to another a few days before symptoms occur because there are high levels of virus and the virus then causes disease symptoms – this depends on how the virus is transmitted and that is not fully understood at present – it is known that this virus can pass from one to another through close physical contact, and more and more evidence suggests that it can be passed by droplets that spread face to face by a cough or sneeze directly on the face from one to another as was SARS. As this is a newly identified virus in humans more evidence is required to fully answer the question and that is why it is important for all contacts of persons who develop disease to be identified and observed for fever so that they can be tested if they develop a fever to determine if the fever is caused by the virus.” Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said: “Defining the scale of asymptomatic transmission remains key: if this is a rare event then its impact should be minimal in terms of the overall outbreak. But, if this transmission mode is contributing significantly then control becomes increasingly difficult. It’s looking like this coronavirus is behaving very differently to SARS and MERS, and this is a big concern. I would be surprised if WHO do not declare this as a Public Health Emergency of International Concern.” Sunday 26th January Professor Sheila Bird, Honorary Professorship at Edinburgh University’s College of Medicine and Veterinary Medicine and formerly Programme Leader at MRC Biostatistics Unit, Cambridge, said: “If transmission does occur pre-symptoms or is suspected to do so, at some point soon-ish it may be instructive & important for the Chinese health authorities to try to measure within-household transmission, taking account of household size and ages of members of the household. Little has been said as yet about the estimated fatality-rate for patients whose clinical course is completed (ie recovered alive, or deceased) but I’m sure that public health official know how important it is to do so – even if only for hospitalized cases in the first instance.” Professor Wendy Barclay, Department of Infectious Disease, Imperial College London, said; “Many of the respiratory viruses that spread amongst humans do transmit even in the absence of symptoms, including influenza and
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