In December 2019, an article published at Lancet reported several patients showing symptoms of pneumonia in Wuhan (China, Hubei province) [1], with unknown cause. Their life tracks were linked to a wet animal and seafood wholesale market, and 6 of these patients worked in the market. Medical diagnosis excluded bacterial infection, and on the other hand, a novel coronavirus was isolated from patients’ samples. The following researches confirmed that this coronavirus (named 2019-nCoV) was the cause of the observed pneumonia. In addition, 2019-nCoV shared a lot of commons with SARS virus which outbroke in Guangdong province, China, 2002. First, the nucleic acids of both viruses are RNA, and the sequence similarity is ~85%. Second, human respiratory system is their primary target, causing series of pneumonia symptoms like dyspnea, fever, cough and fatigue. Besides, bats are very likely their primary hosts in nature.
In response to this escalating outbreak, Chinese government declared the highest national emergency plan and took series of measurements, including expansion of hospital capacities, civilian self-isolation, and cease of non-emergency industries. By March 2020, the outbreak in China was contained but the worldwide situation was getting worse, seen from the drastically increasing number of patients (Table 1) [2].
Country | Total confirmed Cases (new) | Total death (new) |
South Korea | 3736(586) | 18(1) |
Japan | 239(9) | 5(0) |
Italy | 1128(240) | 29(8) |
Germany | 57(0) | 0(0) |
U.S | 62(0) | 0(0) |
Table 1. Statistics of 2019-nCoV infected patients, as of March 1st, 2020.
On 27 February, Science reported that a suspected patient in Singapore was confirmed of coronavirus infection, using an experimental antibody test. This is the worlds’ first case of antibody-aided CoV diagnosis. Currently hospitals are using PCR to amplify viral RNA in patient’s saliva or nasal, oral, or anal swabs. But the accuracy of nucleic acid test was estimated to be merely 30-50%. Besides, it cannot identify people if they have already recovered. Antibody test however, also known as serological test, can confirm an infection even after the virus has been cleared. It was developed by Linfa Wang’s team at Duke-NUS Medical School in Singapore. They successfully detected antibodies in blood samples from recovered patients and created synthetic viral proteins for detection without live virus.
The patient in Singapore, together with his wife, were tested negative because of their mild symptoms when they first turned to hospital around 25 January. However, disease trackers identified them as the missing link between two clusters of cases that occurred in a Singaporean church. So, the couple were sent to the National Center for Infectious Diseases for tests on 18 February. Considering that they had already recovered for some time and the virus in their body might have been cleared, researchers run both PCR and antibody tests. Unexpectedly, by PCR, only the husband was diagnosed positive, while the antibody test indicated that both were positive. Many other researchers around the world were also working on it. Although they made progress, and even some of their work has been commercialized, antibody test still needs to be carefully validated to make sure their accuracy and that they can be deployed widely.
References
1. Zhu, N., Zhang, D., Wang, W., Li, X., Yang, B., Song, J., … Tan, W. (2020). A Novel Coronavirus from Patients with Pneumonia in China, 2019. New England Journal of Medicine, 382(8), 727–733. doi: 10.1056/nejmoa2001017
2. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports/