Infected People Without Symptoms Might Be Driving the Spread of Coronavirus More Than We Realized

The coronavirus is spreading really fast among people and due to its outbreak WHO (The World Health Organization) declared COVID-19 pandemic. The scientists are working really hard to find out the reason for its fast spread in order to prevent it. People at most risk are the elderly but also children can contract it and although their lives may not be in stake it is still a serious virus that can cause numerous complications.

According to recently performed studies in several countries the spread is mostly done by the infected people who develop symptoms such as cough, fever, and difficulty breathing. This is in a way good news, meaning that when the infected people are in quarantine the spread of the virus could be stopped.

Yet, these findings are not all true, especially after a Massachusetts coronavirus cluster with at least 82 cases. In this region the virus was transferred by people who have not shown any symptoms. In addition to this, a dozen studies showed that people without symptoms are causing substantial amounts of infection.

You can contract coronavirus by infected person that does not show symptoms

One of the head persons that works in the unit of emerging diseases and zoonoses at WHO is Maria Van Kerkhove, and she says that there is still more to learn about the COVID-19. The early studies have shown that people who have contracted the coronavirus without even showing symptoms can infect other people as well. In this way the virus is vastly spread and that would cause great difficulties in breaking the chains of transmission.

According to Jennifer Nuzzo, an infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security, says that in order these findings to be valid we need more scientific explanation since it is still unclear “to what extent people without symptoms can infect.”

The US Secretary of Health and Human Services, Alex Azar, maintained that the asymptomatic spread is “not the major driver” of the spread, and because of that we need to focus on the symptomatic ones. It is true that asymptomatic transmission can happen for weeks, but maintained it will not substantially contribute to the vast spread of the virus.

The officials at the US Centers for Disease Control and Prevention generally agreed that asymptomatic transmission is not the main way the coronavirus spreads.

However, the administration’s coronavirus response coordinator, Dr. Deborah Birx, has a different opinion stating it when she was asked if people under the age of 20 who do not show “significant symptoms” “are potentially asymptomatic and spreading the virus?”

She answered that “every American to take personal responsibility to prevent that spread.”

Other experts maintain that the transmission by asymptomatic or mildly symptomatic persons contributes to the spread of the virus which before was not taken that much into consideration.

The director of the Center for Infectious Disease Research and Policy at the University of Minnesota, Michael Osterholm, stated that they have understood that “asymptomatic transmission likely plays an important role in spreading this virus”, saying that it is “absolutely clear” that asymptomatic infection “surely can fuel a pandemic like this in a way that’s going to make it very difficult to control.”

Bill Gates, co-chair of the Bill and Melinda Gates Foundation, explains the following:

COVID-19 will be much harder to contain than the Middle East respiratory syndrome or severe acute respiratory syndrome (SARS), which were spread much less efficiently and only by symptomatic people.”

As per the findings of a conducted study “prolonged, unprotected contact” led to first known person-to-person coronavirus transmission in USA. As a result of that many experts fear the possibility of spreading the virus by people without serious symptoms. Dr. William Schaffner, a professor at Vanderbilt University School of Medicine and longtime adviser to the CDC, states that they will be “the drivers of spread in the community.”

Hence, they are urging public officials to explain everything they “know and don’t know” about the transmission of the virus. Currently, there are over 2,000 people tested positive for the virus in the U.S. and 50 of them have lost their lives in the fight against it.

As per conducted study 5 days are needed for the coronavirus symptoms to appear

The employees of Cambridge biotechnology company Biogen attended a company meeting in February, and after the meeting they were tested for the virus. The results were positive although they did not show symptoms during the meeting. This type of transmission was reported by other countries as well coming from asymptomatic or only mildly symptomatic people.

In Germany, Dr. Sandra Ciesek, director of the Institute of Medical Virology in Frankfurt, Germany, tested 24 passengers who had just flown in from Israel. Ciesek reported that 4 passengers had the virus even though they showed no symptoms. What really concerned the doctors was that the viral load of the specimens from the asymptomatic patients was higher than the one of the patients who did have symptoms. This viral load that represents the concentration of the virus in someone’s respiratory secretions is spread to other people and in the case of infected person with no symptoms there is more that makes the spread even higher.

Dr. Sandra Ciesek also reported that she had two passengers who returned to Germany from Wuhan, China. The first one that was tested was positive to coronavirus but without symptoms, and the other passenger was with a mild sore throat and faint rash. The performed tests revealed that both of them “[were] shedding virus that is able to infect cells, and, most likely, other humans.”

The spread of the virus by asymptomatic people were also confirmed by early, large-scale studies of outbreaks in Tianjin, China, and Singapore. These findings were posted on MedRxiv, a pre-print server founded by Yale University, the medical journal BMJ and Cold Spring Harbor Laboratory in New York.

In the Singapore cluster, in 91 infected people 48% to 66% of them contracted the infection from a pre-symptomatic person. In the Tianjin cluster the situation was similar, out of 135 infected people 62% to 77% of the transmission happened from pre-symptomatic people.

However, Tapiwa Ganyani, one of the lead authors of the study, stated that these are not 100% certain estimates. On the other hand, Caroline Colijn, the study’s lead author, that does the mathematics, genomics, and prediction in infection and evolution research group at Simon Fraser University in British Columbia, stated that their analysis suggests that “presymptomatic transmission is pretty commonplace. “

She added:

If I were writing that CDC webpage today, I would phrase that a little more towards transmission before symptoms show up.”

Dr. Sandra Ciesek agrees on this point of view, and said that when she read their statement, she thought “Why are they so sure of this?”

On this issue, a group of experts from USA, France, China, and Hong Kong, in the journal Emerging Infectious Diseases explained how the virus in time transfers to the other person. They have calculated the serial interval of the coronavirus in two people with the virus: the person who infects another, and the infected one. The findings showed that in average the virus appears after 4 days. This study is the first one that evaluates the rate of asymptomatic transmission.

On top of all this research, Lauren Ancel Meyers, a professor of integrative biology at UT Austin, offered the strongest proof of pre-symptomatic transmission by examining more than 450 case reports from 93 Chinese cities. In her released paper more than 1 in 10 infections were from infected people without symptoms.

Meyers stated the following:

This provides evidence that extensive control measures including isolation, quarantine, school closures, travel restrictions and cancellation of mass gatherings may be warranted. Asymptomatic transmission definitely makes containment more difficult.

Our findings are corroborated by instances of silent transmission and rising case counts in hundreds of cities worldwide. This tells us that COVID-19 outbreaks can be elusive and require extreme measures.”

These findings are of great help to the officials how to stop the spread of the virus. Let us obey the regulations and hope for quick recovery of the ongoing pandemic.

Sources:

edition.cnn.com

prevention.com

vox.com