Editor's Note: The number of coronavirus cases keeps rising. The WHO said in its Wednesday's situation report that the risk was "very high in China, high at the regional level and high at the global level." What does that mean? What are the challenges in fighting the coronavirus? CGTN sit down with Amesh Adalja, senior scholar with Johns Hopkins Center for Health Security. The article reflects the expert's opinions, and not necessarily the views of CGTN.

CGTN: The WHO said the risk was "very high in China, high at the regional level and high at the global level." What does that mean?

Adalja: We have a community-based spread going on in several cities in China. And that raises the threat level substantially, because this is something that can become much harder to control when you have human-to-human spread going on in multiple cities and chains of transmission that are very hard to terminate. Likely, there are also going to be mild cases that may be contagious, and they are going to be much harder to identify. And they may be contributing substantially to the burden of illness that you're seeing in these Chinese cities.

CGTN: Under what circumstances is an event categorized as "moderate", "high", or "very high"?

Adalja: There is no consensus of what is moderate, what is severe. It has to do with what's going on in the ground (and) what the experts are saying. I think that this is more of a term of art rather than strict criteria. It more has to do with the general consensus among the experts without any specific direct criteria, I believe.

CGTN: How should people respond to events with "high" and "very high" risks?

Adalja: I think that people should be very alert to the fact that this is an ongoing outbreak that has really severe consequences for disrupting economic and social life in the parts of China that are affected, and that people should be reacting to this with appropriate responses, meaning that they need to really be aggressive at finding cases. They need to be aggressive at linking those cases to care, getting the resources to the outbreak center. We have to be very aggressive now before it becomes an established virus in the human population.

CGTN: What are the challenges in combating the virus at the current stage?

Adalja: It's become clear that the novel coronavirus has the capacity to spread more efficiently human-to-human than SARS could. SARS had difficulty transmitting in humans. The virus used health care centers and superspreaders to be able to infect the 8,000 people or so it affected throughout the world. The coronavirus seems to transmit more like a community-acquired coronavirus. It has that transmissibility characteristic, at least it appears so in China.

The biggest challenge is the fact that this is now transmitting in the community. There's human-to-human spread going on in the community. And that can be very hard to stop. There's also going to be a spectrum of illness. So some people are not going to be very ill, they may have mild symptoms. They may not even realize that they are that sick and they can yet still spread this to other individuals. That becomes very challenging for public health officials to stop. So those are the two main issues that we face right now.

CGTN: What lessons can the international community learn from the outbreak?

Adalja: This (coronavirus) was getting mixed up with cases of flu and ordinary pneumonia. And it really shows that you have to be serious in diagnosing unexplained illnesses, even if they're mild, even when there's not an outbreak, because this may have been discovered earlier, and then we would have had a head start. Instead, by the time they noticed it, it probably was already widespread in the community, (and) it was going to be much more challenging. So the real lesson here is that we need to be very adept at surveillance, looking for new viruses in every patient that does not have an explainable illness. The government's actions to release the virus' genetic sequence, to communicate with public health authorities and allow the WHO team to be in place are all good signs.

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