The White House is not tracing contacts of guests at the Rose Garden ceremony which is blamed for the coronavirus outbreak among President Trump and his staff. 

The September 26 event where Trump nominated Amy Coney Barrett to the Supreme Court has been linked to the contagion after senior officials sat in close proximity without masks, and more than a dozen guests have since tested positive. 

Nonetheless, a White House official told the New York Times that tracing efforts would go no further than notifying people who had been in close contact with Trump in the 48 hours before he tested positive - not including the garden event. 

Experts warned that hundreds of people could potentially have been infected by the cluster, after California pastor Greg Laurie became the latest person to announce a positive test on Monday after attending the Barrett event. 

'It's not just the 400 people that work in the White House. It's their families that they go home to, it's who they may have been in contact with, their children,' said Boston University public health expert Joshua Barocas. 

'The need for extensive contact tracing, if for no other reason than to protect vulnerable communities that are second or third degree removed, is massively important.'  

Guests at the Rose Garden event were sitting in closely-packed rows of chairs, ignoring the CDC's 6ft social distancing guidelines. 

Trump gathered more than 150 people in the Rose Garden, where they mingled, hugged and shook hands - overwhelmingly without masks. 

There were also several indoor receptions, where Barrett, her family, senators and others gathered in the close quarters inside the White House.  

In the days after the Rose Garden event, Trump attended the presidential debate with Joe Biden in Cleveland, Ohio as well as numerous campaign events.

Hope Hicks reportedly felt unwell on a Wednesday night flight on Air Force One, but not until the early hours of Friday did Trump reveal he had tested positive. 

First lady Melania Trump, press secretary Kayleigh McEnany and former New Jersey governor Chris Christie are among the others who have tested positive. 

Pastor Laurie, the head of California megachurch Harvest Christian Fellowship, announced yesterday that he had tested positive on Friday. 

'My symptoms have been mild so far, and I expect to make a full recovery. I have always taken the coronavirus seriously, and it has tragically taken many lives,' Laurie said in a Facebook post.

'At a time like this, we need to pray for those that have it and avoid politicizing it. If our President and First Lady can get COVID-19, clearly anyone can.' 

Despite the fears of a 'super-spreader' event at the Saturday ceremony, the minimal tracing efforts have focused only on the two days before Trump's diagnosis, not stretching back to the Rose Garden gathering.  

CDC scientists were put on alert to carry out more extensive contact tracing but their help has not been requested, staffers at the agency say.  

The White House insists that its own medical unit is carrying out a 'robust contact tracing program', but potentially infected people have only been notified by email. 

White House officials have relied on daily testing to protect the president from Covid-19, ramping up tests after two staffers were infected in May. 

Trump is 'tested more than anyone, multiple times a day. And we believe that he's acting appropriately,' McEnany said in July. 

However, experts warn that cases can be missed in the early stages of infection, meaning that testing is not a totally effective shield against Covid-19.  

When the virus enters the body, it takes over a cell's machinery to copy itself, while fending off the body's immune defenses. 

But the process takes a few days, so people can be infectious for a while before viral particles can be detected by a test. 

'The reliance on a rapid test, with its limitations, unfortunately gave the White House and its staff a false sense of security that they were in control of the virus,' said William Schaffner, a professor of infectious diseases at the Vanderbilt University School of Medicine. 

'You cannot rely on that test to create a barrier between you and the virus,' he said, adding that people 'have to wear masks, do social distancing and not go to all these rallies.' 

The White House uses a testing kit called ID NOW made by Abbott Laboratories which produces results in 13 minutes or less. 

But the company acknowledges that its testing kit cannot detect the virus immediately after somebody becomes infected. 

'It's helpful to keep in mind that tests discover the presence of coronavirus once there's enough viral material in a person to be able to detect it,' a spokesman said. 

The Food and Drug Administration says the Abbott ID Now test is meant for people who are suspected of being sick, and a negative result doesn't rule out Covid-19.  

'Testing alone doesn't prevent disease spread,' said Dr Cyrus Shahpar, a former CDC scientist now at the nonprofit group Resolve to Save Lives.

The main benefit of testing, Shahpar said, is to identify people with infections and isolate them before they can spread the disease to others.

'Tests can have false positives and false negatives, and no test is perfect. It is also just a snapshot of the situation when the person was tested,' Shahpar said.