China has relaxed many restrictions after implementing a zero- Covid policy. Experts are concerned that the U-turn may cause problems. We looked at why.

What has happened in China?

China used to follow a zero- Covid policy that included strict lockdowns and quarantining those who tested positive. In response to protests, China made an abrupt U-turn, abandoning many of its restrictions.

Domestic travel restrictions and the use of its primary Covid tracking app have been removed. People with Covid have been allowed to stay at home and visitors from overseas will no longer have to stay in the country during the winter.

What is the current Covid situation in China?

There are reports of hospitals under intense pressure in China. Last week China changed the definition of Covid deaths so that only patients with the virus who die because of pneumonia and respiratory failure now qualify.

Why is China experiencing such a bad wave?

There are many reasons The population of China has little protection against the virus due to the use of a less effective vaccine and the relaxation of restrictions giving the virus a greater chance to spread.

Few people have had Covid before. There isn't much natural immunity in the current wave.

Many people are getting Covid at the same time, and need hospital care, leading to mounting pressure on the healthcare system.

Is the reversal of policy a concern?

The shift away from a zero- Covid policy has been welcomed by some. New Zealand and South Korea were the first countries to loosen their restrictions. These countries have used safe and effective vaccines and treatments to offer protection from the worst outcomes.

The sudden shift in policy is concerning for China, as the fact that very few people have had Covid means that they have lower overall immunity, particularly in the vulnerable.

Changes in the genetics of the virus and the impact of the current wave in China are two concerns.

Prof Kao of the University of Edinburgh said that there is a lot we don't know about the infections in China.

Should we be worried about new variants arising in China?

Extra travel requirements have been put in place for visitors from China.

According to experts, the number of new cases in countries with high Covid infections won't be affected by the restrictions. The approach could shed light on the variant at play in China if positive samples from such testing are sequencing.

The use of border restrictions to keep out new variant has not worked well in the past, according to experts. Prof Mark Woolhouse of the University of Edinburgh said that border closings have affected almost all arrivals.

The main driver for changes to the virus is the shift in the immune landscape, which is why Prof Tom is not concerned about the possibility of new variant emerging in China.

He said that the required standing genetic variation is in patients with chronic infections.

Covid has high circulation around the world and can be found in many countries.

Most recent versions have adapted to avoid immunity. She said that since the immunity in China is low, there is no need for the virus to evolve. I am not expecting there to be a lot of evolutionary pressure to see new variant out of China, at least not ones that threaten the rest of us.