This is our daily update of breaking COVID-19 news for Tuesday, August 18th, 2020. Previous daily updates can be found here, and up-to-date statistics are here.

New York City is in Phase 4 of reopening now, which includes zoos, botanical gardens, and professional sports (without fans). A look at preparing for the spread of coronavirus is here, and if you have lingering questions about the virus, here is our regularly updated coronavirus FAQ. Here are some local and state hotlines for more information: NYC: 311; NY State Hotline: 888-364-3065; NJ State Hotline: 800-222-1222.

Here's the latest:

1:30 p.m. Mayor Bill de Blasio on Tuesday signed an executive order that requires New York City hotels and short-term rentals to ensure that travelers from designated states with high coronavirus infections fill out a state health form before allowing them access to rooms.

"We have to get serious about the fact there is a real danger here," de Blasio said during a morning press conference.

He described the latest executive order as "another tool to our arsenal." Under the order, hotels and even Airbnb hosts must require guests from the restricted states to fill out the state's health form before accessing their room. The form, which asks for itinerary and personal contact information, can be accessed online. Guests only need to show proof that they have completed it.

"Any hotel, any short term rental must get that form from the traveler complete with the contact information and if they don't have that form from the traveler, they should not give them access to their room. Period," de Blasio explained.

As virus infection levels rise across the country, New York City has grown increasingly worried about infected travelers. Under a state order, people from high infection states must quarantine for a period of 14 days if they are staying in New York for more than 24 hours.

As of Tuesday, 35 states or U.S. territories meet the state's quarantine criteria.

Dr. Jay Varma, the mayor's top health adviser, on Tuesday said that over the past month about 15% to 20% of cases have been attributed to people who have recently traveled outside the city.

Earlier this month, de Blasio announced the creation of checkpoints at Penn Station as well as major bridge and tunnel crossings to alert people about the quarantine rule, although it was not clear whether the message was being taken seriously by many travelers.

The mayor said members of the city sheriff's office would be expanding their presence in an effort to get the word out.

Both New York and New York City have among the lowest infection levels in the country. Within the five boroughs, daily cases have fallen below 200, while the positive testing rate has been below 2% for more than month. As of Tuesday, the city's positivity rate stood at 1.56%. Going forward, the city's new warning threshold for positive tests will stand at 5% rather than 15%.

During his press briefing, the mayor also said that the city would add new statistics to its website of daily indicators, most notably, introducing antibody test results by zipcode that includes a breakdown by age, borough, income level, and sex.

The city is said to be the first municipality in the nation to present antibody data in this way.

Beginning on Tuesday, the coronavirus data site will also include case fatality numbers, and positivity rates for most recent four-week period.

Reflecting a new stage in the crisis, the city will no longer report the number of new ICU patients.

"Groundbreaking" Saliva Test For Covid May Have A Weakness

A new potentially "groundbreaking" saliva test granted emergency authorization use by the U.S. Food and Drug Administration may have one critical flaw.

On Tuesday, Anne Wyllie, one of the Yale researchers spearheading the product, cautioned that the test could fail to detect people with low infection levels.

“There’s more of a chance that we might miss that very, very low viral load, so when the virus is only starting to pick up in an individual,”  Wyllie said on CNBC.

However, she stressed that regular testing could help overcome such a weakness.

“We’re wanting that frequent testing. So if you’re being tested twice a week — even better if you can be tested more — you might get missed one day if you’ve got very, very low amounts of the virus in you. But if that viral load starts to increase, because you’re having frequent testing, we’ll quickly pick that up the next time,” she said. 

Other scientists have also found that frequency of testing and rapid turnaround time is secondary to accuracy in the surveillance of COVID-19.

New York City is still weighing whether to acquire the test.

"We are still evaluating this platform and technology. Different means of testing can have varying degrees of reliability and we would want to be sure that this platform is effective in the populations we intend to test before we procure and put it to use," said a Department of Health spokesperson.

On Saturday, the inexpensive saliva test was described as a potential game changer for mass coronavirus testing.

Developed by the Yale School of Public Health and known as SalivaDirect, the test requires a small sample of saliva as opposed to the widely used nasal swabs, which are more invasive and have been prone to shortages.

In June, a research team at Yale began using the saliva test on select players, coaches, and staff from certain NBA teams as part of a trial funded by the league. The scientists compared results of the saliva tests to nasal swab tests the same group also took. They found that the saliva tests were both highly sensitive and produced similar results to nasal swab tests. The saliva is also self-collected, reducing the risk to healthcare workers administering the test. It can also be used with several types of reagents, giving it more flexibility to respond to different shortages in key testing materials.

“The SalivaDirect test for rapid detection of SARS-CoV-2 is yet another testing innovation game changer that will reduce the demand for scarce testing resources,” said Assistant Secretary for Health Admiral Brett P. Giroir, in a statement on Saturday.

FDA Commissioner Stephen Hahn called the new test "groundbreaking," while other experts expressed excitement over the development.

Andy Slavitt, the former director of Medicare and Medicaid in the Obama administration, wrote on Twitter, "They are turning testing from a bespoke suit to a low cost commodity. I’ve been writing about this goal for months."

This marks the fifth saliva test the FDA has approved. It comes as the country continues to be hampered by delays and shortages in testing, which some have warned will only worsen once the flu season begin.

Nathan Grubaugh, one of the developers of the test at Yale, said in a press release that one of the aims was to minimize the cost of the test by eliminating the need for special saliva tubes. The cost of testing materials is only a few dollars. He expects labs will only charge about $10 per sample. During the pandemic, charges for diagnostic tests have varied wildly, from $27 to more than $2,000 in some cases.

Following the FDA's emergency use authorization, the new saliva test is immediately available to laboratories. The Jackson Laboratory for Genomic Medicine in Farmington, Connecticut, will partner with Yale to work on a plan for a broader rollout of the test.

"If cheap alternatives like SalivaDirect can be implemented across the country, we may finally get a handle on this pandemic, even before a vaccine,” said Grubaugh.