- The official number of cases of COVID-19 has now topped 7,800. But experts believe the number is likely much higher.
- A lack of testing kits means many people with symptoms have not been tested.
- Without robust testing, health officials are having a hard time determining the scale of the outbreak.
As alarming as the current world crisis may be, the actual numbers of people with the novel coronavirus (SARS-CoV-2) that causes the COVID-19 disease could be much higher than confirmed cases.
A new report based on data from China finds that for every known case of infection, there could be up to 10 people with the virus that remain unidentified in the community.
This means that the more than 7,700 cases confirmed to date in the United States may be the tip of a very large iceberg. Based on that report it’s possible another 77,000 people or even more have the virus already in the United States — although it’s difficult to determine due to differences in how the outbreaks started in each country and the ability for each country to test for the virus.
“It’s truly hard to predict the number of possible cases, but in public health we use what is called an iceberg phenomenon to help give us an idea of what lays ahead,” Dr. Rosie D. Lyles, MHA, MSc, Director of Clinical Affairs at Medline told Healthline.
She explained that this describes a situation in which a large percentage of a problem is subclinical, unreported, or otherwise hidden from view. So, only the “tip of the iceberg” is apparent.
According to public health scientists at Columbia University, these “undocumented infections” often experience mild, limited, or no symptoms at all, and go unrecognized. They also found that, depending on their contagiousness and numbers, these people may expose a much greater portion of the population to infection than would otherwise occur.
“The explosion of COVID-19 cases in China was largely driven by individuals with mild, limited, or no symptoms who went undetected,” says co-author Jeffrey Shaman, PhD, professor of environmental health sciences at Columbia University Mailman School of Public Health, in a statement. “Depending on their contagiousness and numbers, undetected cases can expose a far greater portion of the population to virus than would otherwise occur.
The findings suggest that those people whose coronavirus infections remain undetected may unwittingly spread up to two-thirds of COVID-19 infections.
The researchers used a mathematical model based on travel data, as well as the most recent information on the disease’s incubation period and infection rate, to simulate the current pandemic from its earliest days in the Chinese city of Wuhan. The model incorporated data from infections across 375 cities in China and categorized infections based on whether they were documented, observed, or undocumented infections.
Investigators analyzed multiple models, but they concluded the “best-fitting” model estimated that over 13,000 total new infections, documented and undocumented, occurred from January 10 to January 23 in Wuhan, China.
They also found that before Chinese authorities restricted travel in and out of Wuhan, up to 86 percent of cases likely went undetected.
The report finds that undetected cases were responsible for the greatest share of the infections spread in Wuhan. Although the study authors emphasized that these people are only 52 percent as contagious as those who show obvious symptoms.
“The only way to confirm is by testing everyone,” said Dr. Nikhil Bhayani, infectious disease physician with Texas Health.
This suggests that being tested and practicing social distancing could be essential measures — even for those who don’t have symptoms.
“We find for COVID-19 in China these undetected infected individuals are numerous and contagious. These stealth transmissions will continue to present a major challenge to the containment of this outbreak going forward,” said Shaman. “If the novel coronavirus follows the pattern of 2009 H1N1 pandemic influenza, it will also spread globally and become a fifth endemic coronavirus within the human population.”
The researchers also found that government control efforts and population awareness have reduced the rate of COVID-19 spread in China. Also, after travel restrictions and control measures were imposed, the infection spread less quickly.
Bhayani emphasized that testing is key to resolving the need for stringent travel restrictions. “If there is a lot more testing and negative results, then it would reduce the risk of lockdowns and travel restrictions,” he said.
Compared to a nation like South Korea (with just 51 million people), the United States has tested a much lower percent of its population of 329 million.
South Korea has tested about 250,000 people since its outbreak began on January 20, with a daily capacity of 15,000. They’ve conducted 3,600 tests per million people compared to only 5 per million in the United States, according to NPR.
To date, there have only been about 32,000 COVID-19 tests performed in the United States, according to the
“Because our country is lagging in testing, it makes it challenging to test someone and then quarantine,” said Lyles. “If we had enough tests, we would be able to screen patients more effectively. That is why the government is asking everyone to practice social distancing to slow down the spread of the virus.”
However, the sheer number of visitors has overwhelmed the website’s capacity, according to CNBC.
Part of President Trump’s response to the pandemic is partnering with a Google subsidiary to help Americans find out if they should go get tested at drive-through facilities that are supposed to be available nationally.
“Californians will be able to take an online COVID-19 screener survey through Project Baseline beginning Monday, March 16,” the company Verily said in a blog post. “People who meet eligibility and requirements for testing will be directed to mobile testing sites based on capacity.”
Unfortunately, it’s not as expansive as Trump claimed it would be; that website only serves California’s San Francisco Bay Area.
A new report based on data from China finds that people with undiagnosed cases of COVID-19 transmit the majority of new infections.
Experts say travel restrictions and testing are the two most effective ways to slow down the spread of disease.
The United States is unprepared for the huge number of tests that must be conducted to slow the spread of the virus due to undiagnosed cases and people with mild symptoms who don’t self-isolate.