The number of COVID-19 cases aboard the Diamond Princess cruise ship top 540 as Britain announces steps to evacuate citizens. Health officials around the world continue to battle an outbreak of respiratory disease, first detected in the central Chinese city of Wuhan in December. The causative agent was traced to a novel coronavirus, dubbed SARS-CoV-2, which has now infected more than 75,000 people and claimed over 2,000 lives. The spate of illness was first reported to the World Health Organization on New Year’s Eve and in the following weeks was linked to a family of viruses known as coronaviruses, the same family responsible for the diseases SARS and MERS, as well as some cases of the common cold. On Feb. 11, WHO and other organizations agreed to name the new illness COVID-19 (for “coronavirus disease 2019″). A special WHO committee declared a public health emergency on Jan. 30, citing “the potential for the virus to spread to countries with weaker health systems.” Human-to-human transmission has been confirmed, including in the US, and authorities around the world have limited travel and enforced quarantines to guard against the spread. Some of t...