On March 4, California officially registered its first day with 10 new Covid-19 infections.
New California Covid-19 Cases Daily
By January 24, there was a greater than 50% chance that 10 new people would be infected every day.
Probability of a single day with at least 10 locally transmitted infections
In fact, researchers now estimate that California hit that milestone more than a month earlier.
It had spread across America before anyone reacted.
The Covid storm
Months before travel bans and lockdowns, Americans were spreading the virus across the country
Posted Oct 8, 2020 at 1
The Wall Street Journal interviewed detectives of the disease and went through hundreds of pages of new research to piece together how the coronavirus infiltrated the richest nation on earth. The latest genetic, epidemiological and computational research suggests it was spreading within the country before anyone started looking for it.
How did it happen?
In this photo from Saturday, March 15, 2020, travelers wait in line to clear customs at Chicago’s O’Hare International Airport. PHOTO: Michael Sadler / Associated Press
Probability of only one day with at least 10 locally transmitted cases
Retrospective testing in Ohio found that five women and one man who developed Covid-like symptoms in early January had antibodies to the virus, qualifying as “probable” infections. They lived in opposite corners of the state, up to 200 miles away. Although inconclusive, modeling experts say these findings are consistent with the speed of the subsequent spread of the pandemic.
Screening has begun on air travelers, but only on those from Wuhan, China, where the virus emerged, and only at San Francisco, Los Angeles and New York’s JFK airports. A handful of sufferers have been identified, but scientists say others have escaped. By the end of January, more than half a million people had flown from China to the United States.
While the country was still looking outward, researchers now believe that the first infections in many states came mainly from travel within the United States.
Probable sources of infection for the first cases with local transmission
By this time, the virus was likely spreading to 10 new people every day in California, according to researchers from Northeastern University’s Network Science Institute.
With the virus sneaking into the US, the country has banned arrivals from China to non-US residents.
The disease was taking root in New York. Subsequent genetic analyzes show that by this date at least seven distinct strains may have arrived in New York City, mainly from Europe and the United States.
A 57-year-old woman died in Santa Clara County, California. Subsequent tests found she had the coronavirus, making her the first known death from Covid-19 in the United States. It is not yet known how he got the virus.
US testing had largely halted earlier this month due to problems with test kits. The odds were good that the virus had taken hold in as many as 15 states, researchers in the Northeast found. In Colorado, the spread likely began among skiers arriving in the high season, according to David Bortz, a professor of applied mathematics at the University of Colorado and a member of the state’s Covid-19 modeling team.
By now it was more likely than not that local transmission of the virus was taking place in 24 states.
A swab taken from a door handle of a public building in Gainesville, Florida for a routine flu study was later discovered to carry the virus. Genetic analysis showed that the strain was closely related to the samples found in the Puget Sound area in Washington this same week.
How did the disease spread so quickly? Large gatherings, such as the Biogen conference in Boston on February 26-27, played a role. A variety probably imported from France has spread among the participants. Genetic reconstruction and case histories show it took him to North Carolina, Tennessee, and Texas. Sequencing shows that the strain has also established itself in Massachusetts and Virginia.
At the end of February, there was a more than equal chance of local transmission of the virus in 37 states, models from Northeastern researchers show.
Why was the country in darkness? The lack of testing played a role. Researchers believe we were seeing a much lower percentage of symptomatic Covid-19 patients in mid-February than at the start of the month.
Estimated share of symptomatic Covid-19 infections detected by tests
95% confidence interval
Cruises were another carrier. In early March, attention was focused on the Grand Princess, a ship blocked from docking in San Francisco. But as of February 11, more than 100 people who later tested positive for Covid-19 have set sail for nine different Nile River cruises. They have spread across 18 states and the District of Columbia, the U.S. Centers for Disease Control and Prevention said.
Number of confirmed cases linked to nine Nile River cruises, by patient status of
The agency did not ban cruises in US waters until March 14, two days before the US closed its doors upon the arrival of most air travelers from Europe. At this point, the virus was firmly embedded across the country.