Instead of the 14-day quarantine, the new US CDC guidelines state that people who are in close contact with nCoV infection may need only 7-10 days of isolation.

According to new guidelines updated by the US Centers for Disease Control and Prevention (CDC) on December 2, people in close contact with nCoV infections can stop quarantine after 10 days without having a negative test result.

However, the agency also said a 14-day quarantine period, which includes staying at home and avoiding contact with others, is still considered the safest option if they have ever had close, less than 2 meters in less contact.

The CDC's notice states that the agency recommends a 14-day quarantine, but admits that "shortening the time can help reduce the economic burden" and pressure on the public health system compared with implementing

"The new guidelines are examples of harm reduction approaches, or take into account the challenges individuals may face in reducing risks," said Jen Kates, director of universal health policy.

The incubation period of Covid-19 can be up to two weeks or even longer in some cases.

The CDC change comes as the US is recording chronically increasing infections.

Observers see the quarantine guidelines as the CDC's attempt to encourage Americans to take measures to prevent Covid-19, as many have opposed other measures it calls for.

During the news conference on the new recommendations, the CDC official made it clear they still encouraged people to quarantine for a full 14 days after exposure to the case.

"We can safely reduce quarantine times, but there is also a small risk that people who end quarantine early can infect others if they become infected," said John Brooks, director

German Lopez, editor of Vox, says that the biggest risk facing the new CDC guide is that scientists do not fully understand Covid-19, from the incubation period, the symptoms to the

Some experts have criticized the CDC's new guidelines, calling for more clarity or correction on recommendations.

Ms. Popescu also added that the CDC and many other officials should also have clearer recommendations on restrictions and further encouragement to take other steps, such as social stretching when possible and wearing masks.

Experts say the biggest risk is that the US is in the middle of a serious outbreak.

However, not everyone listens to the recommendations of health officials.

This can happen again during Christmas and New Year, with the risk of outbreaks of new super infectious events, aggravating the pandemic.

The United States remains the world's largest epidemic zone with nearly 14.5 million cases and more than 280,000 deaths from Covid-19.