Two weeks into social distancing and early data has indicated San Francisco's coronavirus curve could be flattening.

Prior to the regulations, the Bay Area officials were concerned with how Covid-19 infections would impact the community.

San Francisco Mayor London Breed and five mayors in the surrounding Bay Area issued a stay-at-home order on 16 March in response to concerns, an unprecedented move at the time. Then California Governor Gavin Newsom quickly followed his city mayors by ordering a statewide state-at-home order to the nearly 40m residents.

In New York, by comparison, the current US epicentre for the pandemic, Governor Andrew Cuomo waited to issue a stay-at-home order. It went into effect almost a week later on 22 March. This order was in partnership with Connecticut and New Jersey to help combat the spread of the virus.

Now San Francisco has only 374 cases and six people have died from the novel virus. In the 10 Bay Area counties, there have been more than 2,200 confirmed cases and 57 deaths. Comparatively, New York City has 43,139 cases and 932 deaths, as of Tuesday. Authorities warn that this death toll will go up.

So was it the early intervention of California officials that helped flatten the curve on the west coast?

Potentially, but Dr George Rutherford, professor and epidemiology & biostatistics director at the University of California, San Francisco, tells The Independent it is too early for the Bay Area to determine if the curve is actually flattening.

"Our official line is it is too soon to call. It could all go south tomorrow," he said.

One factor that contributed to government officials closing down San Francisco early is it is the "densest and oldest county", with more people over the age of 65 compared to the rest of California.

Dr Robyn Gershon, clinical professor of epidemiology at NYU School of Global Public Health, also said the county had early warning signs of how the virus could be spreading in the US.

"San Francisco had a little bit of early warning because they are so close to the Asian countries," she said.

Warning signs also came from the Grand Princess cruise ship, which sailed just outside San Francisco for days before it was able to dock on 10 March. Companies like Apple and Google, both based in Silicon Valley, allowed their employees to stay home starting as early as 5 March.

While this was all happening, millions of people every day were still taking the New York City subway and bus systems, which Dr Gershon said potentially aided the exponential spread in Manhattan.

"I think what really helped them is that (San Francisco) doesn't have mass transit," the epidemiologist said. "New York City has kept open the mass transit because so many depend on it."

"It is very easy to spread," Dr Gershon added. "It seems to spread from one person to three."

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When comparing New York City and San Francisco, similarities include both having high rates of a vulnerable elderly population, homeless people, and people living below the poverty line. These variables can contribute to each city getting hit harder with the virus compared to other parts of the US. But San Francisco isn't seeing quite the same hit.

"We are way outstripping them," Dr Gershon said about the number of cases and hospitalisations in New York City, adding: "When you think of San Francisco and the counties, yeah they have a lot of people but in San Francisco ... it is not dense. It's not the dense close living that we have here."

Dr Jeremy Greene, professor and director of the Institute of the History of Medicine at Johns Hopkins School of Medicine, warned against comparing New York City and San Francisco based on how quickly regulations were put in place.

"I think that it's a dangerous game to compare the differential epidemic in New York City in San Francisco," he said. "Yes, we know that California did put into place shelter-in-place orders earlier than New York ... but I don't believe that the difference that we are seeing between New York and San Francisco can be attributed to a political will-to-action."

Covid-19 differs from that of influenza because people show little to no symptoms for weeks after first being infected.

"While we have earlier evidence of community spread in California over New York, we have no reason to believe that is the truth of the epidemiology," Dr Greene added. "Coronavirus could've been spreading in the New York area for far longer and clearly spreading in a denser capacity."

The number of cases in every city and state has not been the most reliable factor when determining how Covid-19 has impacted the area because of the lack of testing capabilities in different parts of the US.

"Unlike influenza - where the disease manifests and it is clearly influenza - coronavirus is so silent that in the absence of a robust testing form, we're operating blind," Dr Greene said. "The United States had several opportunities to aggressively ramp up and employ proper screening mechanisms on a level that South Korea deployed, and we failed to do so. And at this point we have no capacity to do so."

In New York City, 89,197 residents have received tests for Covid-19 and more than 200,000 people in the state. California, in comparison, has only tested 89,600, as of last week. But case numbers in each area could be exponentially higher given how silent Covid-19 symptoms are in carriers.

Hospitalisations and death rates are stronger indicators on how the virus has impacted communities, but even that data can be flawed in understanding the true level of the pandemic.

"The ICU hospitalisations are higher than we would've thought relative to the other ones," Rutherford said about the Bay Area. Of the total number of California cases, 1,432 hospitalisations and 597 people are the ICU, a number that tripled from the weekend.

Santa Clara, which has been hit the hardest in the Bay Area, reported 125 hospitalisations. New York City has more than 7,741 people hospitalised, 1,700 of which are in the ICU.

Stay-at-home orders impact on states like California and New York will not be seen for another few weeks as less and less people are coming in contact with each other.

"It's going to take a couple of generations, 10 to 14 days, to see some peaking in the curve," Dr Rutherford said. "And that is assuming the effect (of the virus) happens instantly."

The epidemiologist added even though signs are cautiously showing the curve could be flattening, this was not the time for the Bay Area to lift regulations. Instead, it was announced the stay-at-home order across California would extend until 1 May.

"You have to be cautious about this stuff," he said. "This is the time to save those 10 to 20,000 (lives)."

New York City has been clear that additional weeks are needed to determine where the curve is going, and Mr Cuomo said that apex could happen in seven to 21 days. New York state's stay-at-home order was extended through 15 April with the anticipation for it to get pushed back again.