Coronavirus declared global health emergency by WHO after 1st person-to-person US case reported

The World Health Organization declared coronavirus a public health emergency of international concern at a news conference Thursday in Geneva.

This is only the sixth time such an emergency has been declared, with past examples including the Ebola outbreak in the Democratic Republic of Congo and the Zika virus.

The WHO reserves the designation for "extraordinary events" that pose a public health risk by threatening to spread internationally.

The first case of human-to-human coronavirus transmission in the U.S. has been confirmed, in a patient in Illinois, the Centers for Disease Control and Prevention announced Thursday.

The transmission occurred between a husband and wife, who were in close contact with one another. The wife, a woman in her 60s, had traveled to Wuhan, China, and was diagnosed with the virus last week. The husband, a Chicago resident also in his 60s and who has underlying health problems, had not traveled to China.