On Dec. 29, 2019, four cases of a mysterious pneumonia were reported in Wuhan, China, now known as having been caused by the 2019 novel coronavirus (2019-nCoV).
These patients were linked to a live wild animal market, indicating that the infection may have originated from animals. It is believed that the virus came from bats, but how it spread to humans remains unknown.
Forty-four cases were reported by Jan. 3, and person-to-person spread was soon noted. The first travel-related case in the United States occurred on Jan. 21. After spreading to several other countries in less than a month, on Jan. 30 the World Health Organization (WHO) declared the outbreak to be a global emergency.
As of Feb. 3, more than 20,000 cases were confirmed in over a dozen countries around the world, with more than 400 deaths. While 11 cases have thus far been confirmed in the United States, it is worth underscoring that 99% of the cases are in China.
In less than two weeks after the first cases of pneumonia were reported in Wuhan, scientists identified the viral culprit and provided details of the full genomic sequence to public databases, facilitating research around the world.
Diagnostic tests were quickly made available.
While the potential for the spread of this disease is high, there has been an impressive collaborative effort shown by thousands of experts around the world who are working quickly and diligently to contain this epidemic.
The 2019-nCoV strain is one of several other coronaviruses that affects humans. Four coronavirus strains cause the "common cold" and account for a substantial number of benign upper respiratory tract infections.
Prior to the 2019-nCoV outbreak, two other animal-borne coronaviruses emerged in this century and spread to humans around the world: SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome coronavirus).
SARS was due to an outbreak of a similar type of bat-borne coronavirus, which occurred in 2003. SARS spread rapidly across the world -- 8,098 SARS cases were reported from 29 countries -- until the pandemic was controlled by public health measures within six months.
MERS -- less widely spread but more lethal than SARS (with a fatality rate of 36%) -- also originated from bats and is thought to have spread to humans via camels.
The number of 2019-nCoV cases surpassed that of SARS by the end of January 2020, which shows that it is spreading more rapidly, but the fatality rate has so far been lower (approximately 2 to 4% for 2019-nCoV, compared to 10% for SARS).
There is no vaccine yet for 2019-nCoV, as there is for influenza, which the CDC estimates caused roughly 35 million illnesses and 34,200 deaths last year.
While the unpredictable scope and impact of the 2019-nCoV is frightening and the rapid flow of information about it can be overwhelming, it is worth emphasizing the availability of effective vaccines that we do have at our disposal against other infectious diseases, such as influenza and other viruses and bacteria which cause substantially more morbidity and mortality.