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China is grappling to get a surge in Covid-19 cases under control, after the BA.2 variant caused the country’s worst infection rates since the virus was first discovered in Wuhan more than two years ago.

The cause of the rapid rise is the Omicron variant – and its more contagious sub-variant, BA.2, which has already become dominant in the US, Europe and many parts of the world.

But China’s response is very different to almost everywhere else; the nation is sticking with its “zero Covid” policy, even as most others adjust to living with the reality of Covid-19.

On Sunday, the ruling Communist Party announced the deployment of thousands of military personnel to the locked-down city of Shanghai to assist in the mandatory screening of all 25 million inhabitants.

China’s health authorities have repeatedly warned about the potential for health care systems to be overwhelmed if the virus spreads widely in the population of 1.4 billion – especially given the low vaccination rate among the elderly – as they put in place their radical attempts to stamp down infections.

Meanwhile, in the US and Europe, leaders are finding ways to work around Covid-19 as it moves towards becoming endemic. Lawmakers in the Senate agreed on a bipartisan $10 billion Covid aid bill this week that allows the Biden administration to purchase more vaccines, maintain testing capacity and continue ongoing research.

That move comes as companies and several states strip back their last remaining rules; a mask requirement on planes and in airports is set to expire this month, and those leading the country’s response sound increasingly reluctant to impose strict new rules in the near future.

“Lockdown for lockdown’s sake doesn’t make any sense,” Dr. Anthony Fauci, President Joe Biden’s chief medical adviser and the director of the National Institute of Allergy and Infectious Diseases, told CNN last week.

In England, the few remaining Covid-19 measures ended last week, with Prime Minister Boris Johnson encouraging Brits to be “careful and considerate” if they test positive but no longer asking them to isolate.

So, which approach is most appropriate? It’s not a simple answer, according to experts.

“Public health is very much a local thing,” Andy Pekosz, a virologist at the Johns Hopkins School of Public Health, told CNN, with immunity rates dramatically different between countries.

That also means that the spike of cases in China won’t necessarily be replicated elsewhere.

“I expect to see some resurgence (in the US), but it’s a very different picture, even with the increase in the Omicron subvariant BA.2,” added Justin Lessler, an epidemiologist at the University of North Carolina’s Gillings School of Global Public Health.

Lessler said that, given the rate of immunity in the population, a “mild blip” is more likely in the US than the dramatic spike seen in China.


Q: Do I need a second booster shot?

A: Last week, the US Food and Drug Administration (FDA) authorized a second Covid-19 booster for some individuals – adults over 50, and certain people 12 and older who are immunocompromised.

Getting a fourth dose of the vaccine isn’t “something that everyone needs to be getting right now,” said CNN medical analyst and emergency room physician Dr. Leana Wen.

“We know that vaccination, plus that first booster, still protect you very well including against severe disease,” she said. But “some people may want to have an additional level of protection; if you’re over 65, if you have chronic medical conditions and you’re over 50, you may want to get that fourth dose.”

Wen stressed that “everybody who is eligible” should get the first booster shot, noting that many had not yet done so. Then, four months or more after that dose, when you become eligible for another, you may consider whether you’d benefit from the additional booster.

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First human challenge study of Covid-19 yields valuable insights about how we get sick

It takes just a tiny virus-laden droplet – about the width of a human blood cell – to infect someone with Covid-19.

This is what was shown in a study that deliberately infected healthy volunteers with the SARS-CoV-2 virus. The findings of this research were published March 31 in the journal Nature Medicine.

Challenge studies are controversial because they involve intentionally giving someone a virus or other pathogen in order to study its effects on the human body. Even with safeguards in place, there’s an element of risk, particularly when studying a new virus, writes Brenda Goodman.

But they are also hugely valuable for understanding the course of an infection.

“Really, there’s no other type of study where you can do that, because normally, patients only come to your attention if they have developed symptoms, and so you miss all of those preceding days when the infection is brewing,” said lead study author Dr. Christopher Chiu, an infectious disease physician and immunologist at Imperial College London.

There is no ‘magic moment’ to lift Covid-19 restrictions, researchers say

Pandemic hospitalization rates are at new lows in the US, with all 50 states having lifted mask requirements as of March 25. But is there a cost to lifting restrictions and trying to return to a pre-pandemic normal?

In a new study, researchers predict that the lifting of masking and social distancing restrictions in March 2022 could lead to resurgences of Covid-19 deaths in most states, based on projections from a simulation model.

Published Friday in the Journal of the American Medical Association Health Forum, the study also found that delaying lifting restrictions would not prevent surges in deaths for those states, concluding that there is no “magic moment” to lift restrictions, Tasnim Ahmed reports.

The researchers simulated lifting restrictions at different times in the year and predicted the number of deaths that would follow using current estimates for infection and vaccination rates, while accounting for differences in risk between age groups.

“There is likely no amount of additional waiting time in any state after which removing [Covid-19 restrictions] will not lead to a rise in morbidity and mortality,” the study says.

How the next variant could emerge

Where Omicron came from is still a mystery: How did a variant that looked so different from all its older cousins appear so suddenly? How to explain its jumble of mutations, many of which had rarely been seen in variants of interest?

Michael Nedelan reports how the virus we sneeze or cough out may be ever so slightly different from the one we were infected with. This is because viruses mutate – especially when their genetic code is made of RNA, a close cousin of our DNA.

In a briefing in March, Dr. Mike Ryan, executive director of World Health Organization’s health emergencies program, said: “As the virus reproduces itself, there are errors in reproducing its code.”

Viruses change all the time, often in ways that hurt their chances at survival. But once in a while, those mutations can work out in the virus’ favor.


Should you keep wearing a mask on flights?

The rule requiring masks on planes, in airports and on other means of public transportation is set to expire in the US this month.

Experts are split over whether that’s a good idea. Linsey Marr, an expert in transmission of infectious disease via aerosols, told CNN last week that dropping the mask mandate is reasonable with the caveat that it makes sense “as long as cases remain low.”

But you may decide to keep covering up when you’re traveling – and the time you spend in the air is worth factoring in.

“I think I shall certainly continue using a mask for my own protection, especially if I’m going long haul,” said Dr. Richard Dawood, a London-based travel health specialist.

Read more here.


Why do we have such strong emotional connections to music? Well, the answer lies in our brains. On this episode, CNN’s Chief Medical Correspondent Dr. Sanjay Gupta talks to Professor Assal Habibi, a pianist and neuroscientist, about the brain science of music. Listen here.