Researchers from the Icahn School of Medicine at Mount Sinai tested more than 10,000 blood samples for antibodies against COVID-19, the disease caused by the virus.
They found that about 22 percent of samples had antibodies, which means that around 1.7 million people in the city have previously been infected.
That is a more than six-fold increase from the 256,881 infections that have been confirmed by health officials.
Additionally, the team found that some patients had antibodies in late February, several days before New York City’s first confirmed case in March, which indicates the coronavirus was circulating far earlier than previously thought.
Researchers tested coronavirus antibody levels in more than 10,600 blood samples of patients treated at Mount Sinai in New York City. Pictured: A medical worker pushes a stretcher outside Elmhurst Hospital Center in Queens, New York, March 26
Antibodies were detected in 22% of samples, which indicates that at least 1.7 million New Yorkers have been infected – six times more than the official count – with rates as high as 56.7% among urgent care patients (above)
Routine care patients, who were receiving OB/GYN care or cardiac care, saw antibody prevalence as high as 22.2% (above)
‘We saw this virus coming in January and so one idea was to monitor this over time,’ corresponding author Dr Florian Krammer, a professor in vaccinology at the Icahn School of Medicine, told DailyMail.com.
‘The motivation was really to figure how many people would be infected.’
For the study, published in the journal Nature, the team analyzed more than 10,600 blood plasma samples from Mount Sinai Health System patients tested between the weeks ending February 9 and July 5.
Samples were split into two groups. The first group of about 4,100 samples were from patients seen in emergency departments or admitted to the hospital.
This ‘urgent care’ group served as the group representing increasing amounts of COVID-19 cases in the population.
The second group, of about 6,500 samples, was dubbed the ‘routine care group’ who visited for reasons including OB/GYN care, oncology care and cardiac care.
Researchers said these samples might resemble the general population more closely because the purposes for these scheduled visits were unrelated to the virus.
They looked at the presence of coronavirus antibodies, also known as seroprevalence, as well as the level, or titer, of antibodies an individual has.
In the urgent care group, antibody prevalence from as low as 1.4 percent to high as 56.7 percent, with the highest rates seen between late March and late May.
Among the routine care group, prevalence ranged from between 0.9 percent and 22.2 percent, with the high rates reported from June to July.
Testing detected antibodies as early as February 23, which is about one week before the first case was confirmed in New York City (above)
Overall, about 22 percent of samples tested positive for antibodies, which suggests that at least 1.7 million New Yorkers have been infected with SARS-CoV-2 so far.
‘Many of them were asymptomatic, many of them with mild symptoms and those people never got tested,’ said Krammer.
‘And that’s normal because there was very little testing available initially so we can very easily see how’ so many people became infected.’
What’s more, antibodies were detected in samples as early as February 23, seven days before the first confirmed case on March 1.
Between May and July, both prevalence and levels remained stable, which suggests that antibody levels in the population.
Additionally, based on the confirmed deaths, which currently stand at 19,355, the team calculated an infection fatality rate of one percent – about ten times higher than that of the flu, which is 0.1 percent.
‘That’s really high,’ said Krammer.
‘So in a way it’s surprising but also expected because we got hit pretty hard and the healthcare system in New York got overwhelmed.