USA riddled with SARS-CoV-2 - 80% undetected

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The coronavirus pandemic is actively spreading across the globe, affecting 188 countries and territories, and the United States remains the country with the highest number of infections - but actual infections could be significantly higher than official numbers, a new paper reports.

While the official tally reveals that the U.S. has more than 2.347 million people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the new study shows that the number of coronavirus cases in the U.S. in March alone may have been 80 times greater than official estimates.

In the new study, a team of researchers from Penn State University reveal that more than 8.7 million new cases may have gone undetected.

Published in the prestigious journal Science Translational Medicine, the new paper highlights the extent of the coronavirus pandemic in the country, and how it still spreads across populations.

Tracking influenza-like illness surveillance

The predominant symptoms tied to COVID-19, which is caused by the SARS-CoV-2, are fever, cough, and sore throat.

With the symptoms common in both flu and COVID-19, the team studied and reviewed existing surveillance networks to see if the data could be used to help track COVID-19.

During the study period, the patients often present with influenza-like illness (ILI) or flu-like symptoms, yet they test negative for influenza.

“Outpatient ILI surveillance has proven to be a useful tool for assessing the impact of influenza (6, 7). When combined with the number of providers and patients in a given region, ILI surveillance allows estimation of influenza prevalence and severity,” the researchers explained.

To arrive at their findings, the team looked at the number of people who went to clinics or consulted with doctors with influenza-like illnesses that were never diagnosed as coronavirus, flu, or any other viruses that usually circulate in winter.

COVID-19 prevalence in the U.S.

The team revealed that more than 8.7 million new cases of SARS-CoV-2 infections appeared in the country in March, with over 80% of infected patients remaining undetected. Only 100,000 cases were officially reported during the period, and so far, the country has reported 2,347,022 million infections as of today.

Measuring forehead by infrared for COVID-19. Image Credit: Robert Kneschke / Shutterstock
Measuring forehead by infrared for COVID-19. Image Credit: Robert Kneschke / Shutterstock

Many cases are undetected since many of these patients who sought treatment for flu-like symptoms were not tested for COVID-19. Also, during the study period, there was a lack of testing kits in the country, just like in other nations grappling with the coronavirus pandemic. The lack of test kits and with most of the coronavirus cases had just mild to moderate symptoms. Many people recovered without even knowing that they contracted the virus.

“We found a clear, anomalous surge in influenza-like illness (ILI) outpatients during the COVID-19 epidemic that correlated with the progression of the epidemic in multiple states across the U.S. The surge of non-ILI outpatients was much larger than the number of confirmed cases in each state, providing evidence of large numbers of probable symptomatic COVID-19 cases that remained undetected,” the researchers explained.

The surge of flu-like cases in the country without a precise diagnosis may be tied to the coronavirus outbreak, which has spread undetected in the country.

The data suggest that SARS-CoV-2 has spread rapidly across the U.S. since it started on Jan. 15, followed by a large undiagnosed population of COVID-19 outpatients.

“We emphasize the importance of testing these findings with seroprevalence data and discuss the broader potential to use syndromic surveillance for early detection and understanding of emerging infectious diseases,” the researchers concluded.

The data does not include those who were asymptomatic or those who did not manifest any symptoms of the disease at all. This means that the true magnitude of the pandemic is still unclear unless antibody tests will be done to determine how many were infected with the novel coronavirus.

As of writing, the death toll in the U.S. has topped 122,000. Meanwhile, more than 647,000 have recovered from the illness.

Following the U.S. is Brazil, with a staggering 1.145 million cases and more than 52,000 deaths. The other hardest-hit countries include Russia, with more than 598,000 cases, India, with more than 456,000 cases, and the United Kingdom, with more than 307,000 confirmed cases.

Main Symptoms of COVID-19

The three main symptoms of COVID-19 are:

  • Fever – a high temperature >37.8OC/100OF (~86-88% of reported cases)
  • Dry Cough – a new continuous cough that occurs regularly throughout the day (at least 3 coughing episodes per 24 hours) (~69%)
  • Smell and Taste – a noticeable new loss in the sense of smell and taste (variable estimates – data still emerging)

However, not all affected individuals may display all 3 of these symptoms. Often, one of the three symptoms may be sufficient. Furthermore, according to the CDC (U.S.), additional symptoms may include one or more of the following symptoms, which may occur in a subset of affected individuals:

  • Shortness of breath or difficulty breathing (~22%) – depends on the severity of the disease, i.e., in more severe disease this is very common
  • Fatigue (tiredness) (~35-39%)
  • Muscle and body aches (~16-36%)
  • Headache (~12%)
  • Sore throat (~12%)
  • Nausea or vomiting (~4-6%)
  • Diarrhea (~5%)
  • Congested or runny nose (~3%)


The article incorrectly reported  U.S deaths as over 477,000 as of 24th June 2020 AEST when in fact the reported figure is over 121,000.

Journal reference:
Angela Betsaida B. Laguipo

Written by

Angela Betsaida B. Laguipo

Angela is a nurse by profession and a writer by heart. She graduated with honors (Cum Laude) for her Bachelor of Nursing degree at the University of Baguio, Philippines. She is currently completing her Master's Degree where she specialized in Maternal and Child Nursing and worked as a clinical instructor and educator in the School of Nursing at the University of Baguio.


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