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Essential Science: Coronavirus Covid-19 spread ‘underestimated’

The new data relating to zoonotic coronavirus Covid-19 contradicts information supplied by the World Health Organization (WHO). The data is drawn from a detailed examination of earlier studies into coronavirus transmissibility.

MERS virus as seen on electron microscopy.

MERS virus as seen on electron microscopy.
CDC / Wikimedia commons

Virologists from Umeå University in Sweden have looked at the WHO conclusions, where Covi-19 coronavirus is said to have a transmissibility, expressed as a reproduction number, of between 1.4 and 2.5. As Lab Manager magazine reports, the Swedish researchers have come up with a different – and higher – figure.

Virus transmissibility

Viral transmissibility can be considered using different measures. One approach is to assess the reproduction number, which is a measurement of the number of people a contaminated person can transmits the virus to within a given population. The higher the number calculated then the more transferable the virus is considered to be and hence the risk to the general population becomes greater. Such data also indicates the speed of the spread of a virus, since each person infected has the potential to infect the same high number of people.

The COVID-19 outbreak has claimed the lives of eight people in the Islamic republic since Wednesday ...

The COVID-19 outbreak has claimed the lives of eight people in the Islamic republic since Wednesday, the first deaths from the disease in the Middle East

The basic reproduction number, which is used by epidemiologists for a range of infective agents, is influenced by a range of factors, such as the duration of infectivity of affected patients, the infectiousness of the organism, and the number of susceptible people in the population that the affected patients are in contact with.

READ MORE: Gamification is aiding discovery of coronavirus medicine

When the reproduction figure drops below 1.0, then virologists expect a virus to begin to die out and viral transmission rates fall.

New figures for the infectivity of Covid-19

The scientists from Umeå in Sweden teamed up with virologists from Heidelberg in Germany, and Zhangzhou in China, to undertake a detailed review of all published data pertaining to the novel coronavirus.

This review identified twelve studies that contained a suitably rich stream of detailed data. Such research looked at the viral infectivity growth rate by presenting case data in relation to the Chinese population. Such data was then subjected to rigorous statistical and mathematical modelling.

Instead of the coronavirus having a relatively low transmissibility., the new data shows that transmissibility has increased, and it is closer to 3.28 (the mean result from the studies, with a median of 2.79). This puts the rate of viral reproduction at a level far higher than WHO figures, which fall within the range 1.4-2.5.

It should be noted that any estimate of the reproduction number will depend on the estimation method used as well as the validity of the underlying assumptions.

Implications of the new findings

In essence, the new research shows the infectivity rate of Covid-19 is greater than official estimates predict. This means that protective measures need to continue to be enforced, such as isolation, and new methods for controlling population movement and person-to-person contact will need to be considered.

Commenting on the findings, lead researcher Professor Joacim Rocklöv sates: “Our review shows that the coronavirus is at least as transmissible as the SARS virus. And that says a great deal about the seriousness of the situation.”

Furthermore, despite the control measures that have been put into place, Covid-19 has already spread to a far greater extent than SARS.

File photo: Deborah Cannon of the Special Pathogens Branch as she processes SARS specimens.

File photo: Deborah Cannon of the Special Pathogens Branch as she processes SARS specimens.
CDC/ Media / Anthony Sanchez

ALSO READ: Novel coronavirus is very similar to SARS-CoV

Covid-19 and SARS are genetically very similar, and both are enveloped coronaviruses, formed of a single strand of RNA (Covid-19 has the same angiotensin-converting enzyme-2 (ACE2) as SARS). Severe acute respiratory syndrome-related coronavirus (SARS-CoV) is thought to have originated from bats, making a species jump to infect humans, and there was a spate of associated infections in 2003.

Research paper

The new research has been published in the Journal of Travel Medicine, where the research paper is titled “Review of the basic reproductive number for 2019 novel coronavirus.”

Essential Science

This article is part of Digital Journal’s regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue.

FlexCase  a prototype flexible e-ink smartphone cover

FlexCase, a prototype flexible e-ink smartphone cover
Media Interaction Lab / Microsoft Research

Last week we looked at a technological development at that is helping to turn smartphones into portable laboratories, where devices can be used to carry out basic diagnostic tests. Such technology can assist in remote areas where medical services are required.

The week before we weighed in on a research study that considered the microbiome of the human gut and raised the idea that gut bacteria influence how the colon moves. With this insight medics can show how digestion is controlled along with offering new reasons for poor digestive health.

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Written By

Dr. Tim Sandle is Digital Journal's Editor-at-Large for science news. Tim specializes in science, technology, environmental, business, and health journalism. He is additionally a practising microbiologist; and an author. He is also interested in history, politics and current affairs.

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