Professor Stefano Merigliano testing a child in Vo
A study of COVID-19 in the quarantined Italian town of V, where most of the population was tested, reveals the importance of asymptomatic cases.
The authors of the new research, from the University of Padova and at Imperial College London, publishedinNature, suggest asymptomatic or pre-symptomatic people are an important factor in the transmission of COVID-19. They also argue that widespread testing, isolating infected people, and a community lockdown effectively stopped the outbreak in its tracks.
The town of V, with a population of nearly 3,200 people, experienced Italys first COVID-19 death on 21 February 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, both at the start of the lockdown (86 percent tested) and after two weeks (72 percent tested).
The testing revealed that at the start of the lockdown, 2.6 percent of the population (73 people) were positive for SARS-CoV-2, while after a couple of weeks only 1.2 percent (29 people) were positive. At both times, around 40 percent of the positive cases showed no symptoms (asymptomatic). The results also show it took on average 9.3 days (range of 8-14 days) for the virus to be cleared from someones body.
None of the children under ten 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.
As a result of the mass testing any positive cases, symptomatic or not, were quarantined, slowing the spread of the disease and effectively suppressing it in only a few short weeks.
Co-lead researcher Professor Andrea Crisanti, from the Department of Molecular Medicine of the University of Padua and the Department of Life Sciences at Imperial, said: 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.
The results of the mass testing programme in V 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, added Professor Crisanti.
As well as identifying the proportion of asymptomatic cases, the team also found that asymptomatic people had a similar viral load the total amount of virus a person has inside them as symptomatic patients.
Viral load also appeared to decrease in people who had no symptoms to begin with but later developed symptoms, suggesting that asymptomatic and pre-symptomatic transmission could contribute significantly to the spread of disease, making testing and isolating even more important in controlling outbreaks.
Co-lead researcher Dr Ilaria Dorigatti, from the MRC Centre for Global Infectious Disease Analysis, Jameel Institute (J-IDEA), at Imperial College London, said: The V study demonstrates that the early identification of infection clusters and the timely isolation of symptomatic as well as asymptomatic infections can suppress transmission and curb an epidemic in its early phase. This is particularly relevant today, given the current risk of new infection clusters and of a second wave of transmission.
There are still many open questions about the transmission of the SARS-CoV-2 virus, such as the role of children and the contribution of asymptomatic carriers to transmission. Finding answers to these questions is crucial to identifying targeted and sustainable control strategies to combat the spread of SARS-CoV-2 in Italy and around the world.
Professor Enrico Lavezzo, from the Department of Molecular Medicine at the University of Padua said: The result concerning asymptomatic carriers is key. We took a picture of the V population and found that about half of the population testing positive had no symptoms at the time of testing and some of them developed symptoms in the following days. This tells us that if we find a certain number of symptomatic people testing positive, we expect the same number of asymptomatic carriers that are much more difficult to identify and isolate.
The fact that the viral load is comparable between symptomatic and asymptomatic carriers means even asymptomatic infections have the potential to contribute to transmission, as some of the reconstructed chain of transmission obtained from the detailed contact tracing conducted in V confirmed.
On the one hand, it is likely that a symptomatic infection transmits large quantities of virus, for example via coughing, but it is also reasonable to think that symptoms may induce a person with a symptomatic infection to stay at home, limiting the number of contacts and hence the transmission potential. On the other hand, someone with an asymptomatic infection is entirely unconscious of carrying the virus and, according to their lifestyle and occupation, could meet a large number of people without modifying their behaviour.
More:
- Podcast 9 Athens part 3 and news [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Podcast 10 Athens part 4 [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Podcast 11 Athens Part 5 [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 12 Cardiac Nuclear Medicine in the UK [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Podcast 13 Choline PET and prostate cancer [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode14 ED function and Dysponea [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- ep 15 Collimator Choice and Reconstruction algorithm [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 16 Dr Strauss on vulnerable plaque [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode17 Chemical Stress [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 18 Myocardial Perfusion Imaging and Diabetes [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 19 The INSPIRE trial [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- 20 Dual isotope with a difference [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 21 The real effect of stress [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 22 D-SPECT [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 23 VQ Reprise [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 24 Hepatobiliary Nuclear Medicine [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 25 Sleep Apnea [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 26 Imaging Post Traumatic Stress Disorder [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 27 Cardiac Stem Cells [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 28 Molly Supply [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 29 Melanoma therapy interview with Dr Ekaterina Dadachova [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 30 Viral Therapy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 31 breast radiotherapy using radioisotopes [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 32 news from snm [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 33 EBV Imaging and Therapy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Episode 34 Dr Lele SNM India 2009 [Last Updated On: December 14th, 2009] [Originally Added On: December 14th, 2009]
- Episode 35 Dr Andrew Scott from the Ludwig institute [Last Updated On: January 10th, 2010] [Originally Added On: January 10th, 2010]
- Episode 36 CardiArc [Last Updated On: February 25th, 2010] [Originally Added On: February 25th, 2010]
- Episode 37 Dr Modder Radiosynoviorthesis (Radiation Synovectomy) [Last Updated On: March 31st, 2010] [Originally Added On: March 31st, 2010]
- Episode 38 Indian Nuclear Medicine With Dr Malhotra and Dr Krishna [Last Updated On: May 28th, 2010] [Originally Added On: May 28th, 2010]
- Episode 39 Prof Ora Israel The Utility of Hybrid Imaging [Last Updated On: July 13th, 2010] [Originally Added On: July 13th, 2010]
- Episode 40 New V/Q SPECT developments [Last Updated On: October 11th, 2010] [Originally Added On: October 11th, 2010]
- Episode 41 scintimun [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- Episode 42 Radio-Isotope Supply into the future [Last Updated On: March 6th, 2011] [Originally Added On: March 6th, 2011]
- Podcast 4: DNA therapy [Last Updated On: April 24th, 2011] [Originally Added On: April 24th, 2011]
- Sorry about the delay a new podcast will be out soon! [Last Updated On: April 24th, 2011] [Originally Added On: April 24th, 2011]
- Podcast 5 Flash 3D [Last Updated On: April 24th, 2011] [Originally Added On: April 24th, 2011]
- Podcast 6 Affibody [Last Updated On: April 24th, 2011] [Originally Added On: April 24th, 2011]
- Podcast 7 EANM 2006 Athens Part 1 [Last Updated On: April 24th, 2011] [Originally Added On: April 24th, 2011]
- Podcast 8 Athens Part 2 [Last Updated On: April 24th, 2011] [Originally Added On: April 24th, 2011]
- Episode 43 Rapidscan Part 1, 720P high quality video version [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Episode 43 Rapidscan Part 1, Ipod quality video [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Episode 43 Rapidscan Part 1, Audio version [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Episode 45 Mummies with cardiovascular disease video [Last Updated On: May 21st, 2011] [Originally Added On: May 21st, 2011]
- Episode 45 Mummies with cardiovascular disease audio edition [Last Updated On: May 21st, 2011] [Originally Added On: May 21st, 2011]
- Episode 46 Dr Gordon DePuey Choosing Reconstruction clinical perspective [Last Updated On: August 7th, 2011] [Originally Added On: August 7th, 2011]
- Episode 46 Dr Gordon DePuey Choosing Reconstruction clinical perspective audio version [Last Updated On: August 7th, 2011] [Originally Added On: August 7th, 2011]
- Episode 47 Cardiac Image Fusion With Dr Kaufmann [Last Updated On: September 18th, 2011] [Originally Added On: September 18th, 2011]
- Episode 47 Cardiac Fusion with Dr Kaufmann video version [Last Updated On: September 18th, 2011] [Originally Added On: September 18th, 2011]
- Dear Steve, I am and many more like me are your one more thing. [Last Updated On: October 9th, 2011] [Originally Added On: October 9th, 2011]
- EPISODE 48 PET MRI camera from Siemens with Dr Georgi audio [Last Updated On: October 23rd, 2011] [Originally Added On: October 23rd, 2011]
- EPISODE 48 PET MRI camera from Siemens Dr Georgi video [Last Updated On: October 23rd, 2011] [Originally Added On: October 23rd, 2011]
- Silicon Biosystems to Present Single-Circulating Tumor Cell Molecular Characterization at the Fourth World CTC Summit [Last Updated On: April 25th, 2012] [Originally Added On: April 25th, 2012]
- Leukaemia cells have a remembrance of things past [Last Updated On: April 25th, 2012] [Originally Added On: April 25th, 2012]
- Technologist Education Requirements Can Help Cut Repeat Scans [Last Updated On: April 25th, 2012] [Originally Added On: April 25th, 2012]
- HKU Collaborative Research Discovers A Novel Molecular Mechanism Of A New Anti-HIV-1 Drug Candidate [Last Updated On: April 25th, 2012] [Originally Added On: April 25th, 2012]
- Focal Segmental Glomerulosclerosis and the Nephrotic Syndrome - Part 1 Clinical - Video [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- Electro-Medicine : Biological Physics - The Molecular Basis of Alzheimers Disease - Video [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- osdd heterocyclic compounds and molecular medicines - Video [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- Molecule to Medicine: The Biomarker Frontier - Video [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- Fulfilling the Promise of Molecular Medicine in a Developmental Brain Disorder - Video [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- Focus on Stefanie Dimmeler - Video [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- Dundee [Last Updated On: May 4th, 2012] [Originally Added On: May 4th, 2012]
- Nanotechnology In Medicine: Huge Potential, But What Are The Risks? [Last Updated On: May 5th, 2012] [Originally Added On: May 5th, 2012]
- Cutting Edge Technology Coming To DMH [Last Updated On: May 5th, 2012] [Originally Added On: May 5th, 2012]
- This Week in Experimental and Molecular Pathology [Last Updated On: May 5th, 2012] [Originally Added On: May 5th, 2012]
- Researchers' discovery offers hope for cancer, heart disease miracle drugs [Last Updated On: May 7th, 2012] [Originally Added On: May 7th, 2012]
- Penn State student Zachary Hostetler from Garnet Valley is being honored as a student marshal [Last Updated On: May 7th, 2012] [Originally Added On: May 7th, 2012]
- NCKU Student Wins Prestigious Award for Anti-Cancer Research [Last Updated On: May 10th, 2012] [Originally Added On: May 10th, 2012]
- In-Vitro Diagnostics (IVD) Market (Clinical Chemistry, Immunoassays, Molecular Diagnostics, Hematology Analyzers ... [Last Updated On: May 10th, 2012] [Originally Added On: May 10th, 2012]
- Pitt team uses genomics to identify a molecular-based treatment for a viral skin cancer [Last Updated On: May 10th, 2012] [Originally Added On: May 10th, 2012]
- Genomics used to identify a molecular-based treatment for a viral skin cancer [Last Updated On: May 10th, 2012] [Originally Added On: May 10th, 2012]
- 2 molecular biologists get $500K medical prize [Last Updated On: May 13th, 2012] [Originally Added On: May 13th, 2012]
- 2 molecular biologists share $500K medical prize [Last Updated On: May 13th, 2012] [Originally Added On: May 13th, 2012]
- Lab21 Unveils New Molecular Analysis Services at Greenville Site [Last Updated On: May 13th, 2012] [Originally Added On: May 13th, 2012]
- 2 molecular biologists from NYC to share $500K medical prize for pioneering research on cells [Last Updated On: May 13th, 2012] [Originally Added On: May 13th, 2012]
- Two Molecular Biologists Get $500K Medical Prize [Last Updated On: May 13th, 2012] [Originally Added On: May 13th, 2012]
- Pair of molecular biologists receive Albany Medical Center Prize [Last Updated On: May 13th, 2012] [Originally Added On: May 13th, 2012]
- CNIO scientists successfully test the first gene therapy against aging-associated decline [Last Updated On: May 16th, 2012] [Originally Added On: May 16th, 2012]
- Cancer Institute of New Jersey Aims to Advance Personalized Cancer Treatments Through 'Precision Medicine' [Last Updated On: May 16th, 2012] [Originally Added On: May 16th, 2012]