It’s still unclear how long ago it started, but late last year, an illness similar to pneumonia began infecting a number of people in the central Chinese city of Wuhan, population 11 million. 

On Jan. 9, Chinese health officials released the findings of a preliminary investigation into the outbreak, which revealed the sickness could be a new type of coronavirus.

Coronaviruses are a large family of viruses usually signified by mild to moderate upper respiratory tract illnesses. Symptoms include a runny nose, cough, sore throat and possibly a headache or fever.

In the past, coronaviruses such as SARS (standing for Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome) were deadly, especially for the elderly and very young.

So far, the new Wuhan coronavirus has infected close to 300 people and it is blamed for at least six deaths.

Both SARS and MERS were also among a rarer form of coronavirus that is able to be transmitted between animals and humans. Though unconfirmed, it’s suspected that Wuhan’s version first infected a human at a poultry and fish market.

Chinese health officials have since confirmed that human-to-human transmission is also possible.

Outside of China, the international community is responding with calculated caution.

Several dozen Asian countries and three U.S. airports now have screenings for passengers coming from central China.

Despite the precautions, cases of the new coronavirus have also been reported in Japan, Thailand, Taiwan, South Korea and now the U.S.

On Jan. 21, an unnamed male who returned to Washington state from a trip to the Wuhan region of China became North America’s first confirmed case.

Local officials declined to identify the man to The New York Times, but said he was “quite ill.”

The World Health Organization is convening a meeting of coronavirus experts tomorrow in Geneva, Switzerland, to determine whether or not to declare an international public health emergency.