China could be hit with a second wave of the coronavirus because of a lack of immunity among residents, says senior medical adviser

• A lack of immunity could lead to a second wave of COVID-19 infections in China, according to the country's senior medical adviser.
• "Herd immunity" would happen when enough of a population has become immune to the disease to prevent it from spreading, but questions remain about how long that immunity would last.
• The first case of the coronavirus disease was found in China, and lockdowns were enforced starting in late January.
• Restrictions have since eased, with life in the country resuming to some degree of normality.
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China could be hit with a second wave of the coronavirus disease as lockdowns in the nation are slowly eased.

Dr. Zhong Nanshan, a leading Chinese epidemiologist and the country's senior medical adviser, told CNN Saturday that a lack of immunity among Chinese residents could be a cause for concern in spurring another wave of infections.

"The majority of ... Chinese at the moment are still susceptible of the Covid-19 infection, because (of) a lack of immunity," Zhong told CNN. "We are facing (a) big challenge, it's not better than the foreign countries I think at the moment."

The comment comes as some US states are either weighing the prospect of easing lockdown restrictions or altogether reopening businesses — despite some failing to see the recommended 14-day decline in confirmed cases before doing so.

The first case of the coronavirus disease was discovered in China, which has since reported more than 82,000 confirmed cases. The city of Wuhan was first closed in late January, with more shutdowns gradually rolling out across the nation in the following weeks. But by early March, the number of newly reported infections slowed, and parts of the country started reopening. Since then, the series of reopenings have been sporadic, with officials reversing them sometimes days after enforcing them.

Six new cases were found in Wuhan in early May, breaking a 35-day streak of no new infections. Authorities have since ordered all of the city's 11 million residents to be tested for the disease and have not reinstated a lockdown.

Other freshly reported cases have been found in the Chinese provinces of Heilongjiang and Jilin, according to CNN.

"Herd immunity" would occur when enough of a population has become immune to the disease, either through vaccination or through natural infection, to prevent it from spreading.

People who recover from infectious diseases typically develop immunity for a period of time, as Business Insider's Holly Secon reports. A new study found that 99.8% of recovered coronavirus patients that were studied tested positive for antibodies, suggesting that those who have recovered are immune to reinfection. And Dr. Anthony Fauci said in early April that recovered coronavirus patients will likely be immune to a second wave of infections that's likely to spread in the early fall.

But scientists are still deciphering how long that immunity could last. For the disease to enter a decline, nearly 50% of a population would have to be immune either from infection or from a vaccine, which is likely to not be widely available in the foreseeable future.

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