Medical Minutes
New study reveals high infection rates among asymptomatic individuals
A study of COVID-19 in the quarantined Italian town of Vò, where most of the population was tested, reveals the importance of asymptomatic cases. Researchers at the University of Padova and at Imperial College London have published an article in the journal Nature suggesting asymptomatic or pre-symptomatic people are an important factor in the transmission of COVID-19. They report that widespread testing, isolating infected people, and a community lockdown effectively stopped the outbreak in its tracks.
The town of Vò, with a population of nearly 3,200 people, experienced Italy’s first COVID-19 death on February 21, 2020. The town was put into immediate quarantine for 14 days. During this time, researchers tested most of the population for infection of SARS-CoV-2, the virus that causes COVID-19. This was done at the start of the lockdown (86% tested) and after two weeks (72% tested).
The testing revealed that at the start of the lockdown, 2.6% of the population (73 people) were positive for SARS-CoV-2, while after a couple of weeks only 1.2% (29 people) were positive. At both times, around 40% of the positive cases showed no symptoms (asymptomatic). The results also showed it took on average 9.3 days (range of 8 to 14 days) for the virus to be cleared from someone’s body.
None of the children under 10 years old in the study tested positive for COVID-19, despite several living with infected family members. This is in contrast to adults living with infected people, who were very likely to test positive.
“Our research shows that testing of all citizens, whether or not they have symptoms, provides a way to manage the spread of disease and prevent outbreaks getting out of hand. Despite ‘silent’ and widespread transmission, the disease can be controlled,” said co-lead researcher Professor Andrea Crisanti, who is with the Department of Molecular Medicine of the University of Padua and the Department of Life Sciences at Imperial College in London.
The results of the mass testing program in Vò informed policy in the wider Veneto Region, where all contacts of positive cases were offered testing.
“This testing and tracing approach has had a tremendous impact on the course of the epidemic in Veneto compared to other Italian regions, and serves as a model for suppressing transmission and limiting the virus’ substantial public health, economic and societal burden,” said Crisanti.
Wearable device continuously monitors for COVID-19
Researchers in Chicago are introducing a novel wearable device specifically tailored to catch the early signs and symptoms associated with COVID-19. It can also be used to monitor patients as the illness progresses. Researchers at Northwestern University have developed a device that is about the size of a postage stamp. It is soft, flexible and wireless. It sits just below the suprasternal notch, the visible dip at the base of the throat. This allows it to monitor respiratory health.
The team recently added a wearable, flexible pulse oximeter to pair with the suprasternal-mounted device. This allows physicians to continuously monitor for silent hypoxia, an often asymptomatic feature marked by alarmingly low blood oxygen levels. Adding this feature will help the device give a fuller picture of the disease’s onset, progression and response to treatment.
“The device measures very tiny vibrations on the skin and has an embedded temperature sensor for fever,” said team leader bioelectronics pioneer John A. Rogers, who is with Northwestern University, Chicago, Illinois. “As you cough and breathe, it counts coughs, monitors the intensity of cough and senses labored breathing. The location on the throat also is close enough to the carotid artery that it can measure mechanical signatures of blood flow, monitoring heart rate.”
The researchers report that this sensor system targets key symptoms for COVID-19, with the goal to identify the infection earlier in patients. Once it’s placed on the throat, individuals reportedly don’t even realize that it’s there.
Spider NET targeted with umbilical cord blood
An overactive defense response may lead to increased blood clotting, disease severity, and death from COVID-19. A phenomenon called NETosis, in which infection-fighting
cells emit a web-like substance to trap invading viruses, is part of an immune response that becomes increasingly hyperactive in individuals on ventilators and those who die from the disease.
A team led by University of Utah Health now has found that a naturally occurring protein, originally found in umbilical cord blood, quiets this NET immune response in laboratory experiments, potentially opening new avenues for treatment.
“This study tells us about a potential mechanism for lung injury in COVID-19 that had not previously been recognized as a possible target for treatment,” said study investigator Dr. Elizabeth Middleton, who is a critical care specialist at U of U Health, Salt Lake City, Utah.
It is estimated that up to 10% of people with COVID-19 become critically ill with respiratory distress. Causes of lung damage are a subject of intense investigation, and increasing evidence demonstrates that increased blood clotting may lead to complications caused by the disease. As part of an immune response, white blood cells release web-like Neutrophil Extracellular Traps (NETs) to capture and kill pathogens. Researchers have previously shown that overactive NETs exacerbate certain illnesses. In conditions such as overwhelming infection, NETs can clog blood vessels and lead to inflammatory tissue damage.
To determine whether NETs could be responsible for complications seen in COVID-19, the team examined plasma from 33 patients, along with tracheal aspirates from the lungs. They found that NET activity correlated with disease severity. Patients on life support and those who died from COVID-19 had significantly more signs of NET activation than patients who were not as sick or who went on to recover. The NET immune response was lower still in healthy people. NET levels also tracked with a marker for blood-oxygen levels, which are an independent indicator of disease severity.
Larger studies are warranted to determine whether NETs could become a biomarker for COVID-19 severity. However, the researchers theorize that newborn babies have a natural therapeutic in their blood to protect against the deadly inflammatory events associated with COVID-19, and this may ultimately lead to new treatment approaches.
John Schieszer is an award-winning national journalist and radio and podcast broadcaster of The Medical Minute. He can be reached at medicalminutes@gmail.com.
John Schieszer is an award-winning national journalist and radio and podcast broadcaster of The Medical Minute.
