Modern Australian

Writers Wanted

How contagious is the Wuhan coronavirus and can you spread it before symptoms start?

  • Written by C Raina MacIntyre, Professor of Global Biosecurity, NHMRC Principal Research Fellow, Head, Biosecurity Program, UNSW

Cases of the Wuhan coronavirus have increased dramatically over the past week, prompting concerns about how contagious the virus is and how it spreads.

According to the World Health Organisation, 16-21% of people with the virus in China became severely ill and 2-3% of those infected have died.

Read more: The Wuhan coronavirus is now in Australia – here's what you need to know

A key factor that influences transmission is whether the virus can spread in the absence of symptoms – either during the incubation period (the days before people become visibly ill) or in people who never get sick.

On Sunday, Chinese officials said transmission had occurred during the incubation period.

So what does the evidence tell us so far?

Can you transmit it before you get symptoms?

Influenza is the classic example of a virus that can spread when people have no symptoms at all.

In contrast, people with SARS (severe acute respiratory syndrome) only spread the virus when they had symptoms.

No published scientific data are available to support China’s claim transmission of the Wuhan coronavirus occurred during the incubation period.

However, one study published in the Lancet medical journal showed children may be shedding (or transmitting) the virus while asymptomatic. The researchers found one child in an infected family had no symptoms but a chest CT scan revealed he had pneumonia and his test for the virus came back positive.

How contagious is the Wuhan coronavirus and can you spread it before symptoms start? 2-3% of those infected with the Wuhan coronavirus in China have died. Yuan Zheng/AAP

This is different to transmission in the incubation period, as the child never got ill, but it suggests it’s possible for children and young people to be infectious without having any symptoms.

This is a concern because if someone gets sick, you want to be able to identify them and track their contacts. If someone transmits the virus but never gets sick, they may not be on the radar at all.

It also makes airport screening less useful because people who are infectious but don’t have symptoms would not be detected.

How infectious is it?

The Wuhan coronavirus epidemic began when people exposed to an unknown source at a seafood market in Wuhan began falling ill in early December.

Cases remained below 50 to 60 in total until around January 20, when numbers surged. There have now been more than 4,500 cases – mostly in China – and 106 deaths.

Read more: Coronavirus outbreak: WHO's decision to not declare a global public health emergency explained

Researchers and public health officials determine how contagious a virus is by calculating a reproduction number, or R0. The R0 is the average number of other people that one infected person will infect, in a completely non-immune population.

Different experts have estimated the R0 of the Wuhan coronavirus is anywhere from 1.4 to over five, however the World Health Organisation believes the RO is between 1.4 and 2.5.

Here’s how a virus with a R0 of two spreads:

How contagious is the Wuhan coronavirus and can you spread it before symptoms start? The Conversation If the R0 was higher than 2-3, we should have seen more cases globally by mid January, given Wuhan is a travel and trade hub of 11 million people. How is it transmitted? Of the person-to-person modes of transmission, we fear respiratory transmission the most, because infections spread most rapidly this way. Two kinds of respiratory transmission are through large droplets, which is thought to be short-range, and airborne transmission on much smaller particles over longer distances. Airborne transmission is the most difficult to control. SARS was considered to be transmitted by contact and over short distances by droplets but can also be transmitted through smaller aerosols over long distances. In Hong Kong, infection was transmitted from one floor of a building to the next. Read more: Wuhan coronavirus: we still haven't learned the lessons from SARS Initially, most cases of the Wuhan coronavirus were assumed to be from an animal source, localised to the seafood market in Wuhan. We now know it can spread from person to person in some cases. The Chinese government announced it can be spread by touching and contact. We don’t know how much transmission is person to person, but we have some clues. Coronaviruses are respiratory viruses, so they can be found in the nose, throat and lungs. The amount of Wuhan coronavirus appears to be higher in the lungs than in the nose or throat. If the virus in the lungs is expelled, it could possibly be spread via fine, airborne particles, which are inhaled into the lungs of the recipient. How contagious is the Wuhan coronavirus and can you spread it before symptoms start? We still don’t know exactly how it’s transmitted but it could be through fine, airborne particles. David Chang/AAP How did the virus spread so rapidly? The continuing surge of cases in China since January 18 – despite the lockdowns, extended holidays, travel bans and banning of the wildlife trade – could be explained by several factors, or a combination of: increased travel for New Year, resulting in the spread of cases around China and globally. Travel is a major factor in the spread of infections asymptomatic transmissions through children and young people. Such transmissions would not be detected by contact tracing because health authorities can only identify contacts of people who are visibly ill increased detection, testing and reporting of cases. There has been increased capacity for this by doctors and nurses coming in from all over China to help with the response in Wuhan substantial person-to-person transmission continued environmental or animal exposure to a source of infection. Read more: Are you in danger of catching the coronavirus? 5 questions answered However, with an incubation period as short as one to two days, if the Wuhan coronavirus was highly contagious, we would expect to already have seen widespread transmission or outbreaks in other countries. Rather, the increase in transmission is likely due to a combination of the factors above, to different degrees. The situation is changing daily, and we need to analyse the transmission data as it becomes available.

Authors: C Raina MacIntyre, Professor of Global Biosecurity, NHMRC Principal Research Fellow, Head, Biosecurity Program, UNSW

Read more http://theconversation.com/how-contagious-is-the-wuhan-coronavirus-and-can-you-spread-it-before-symptoms-start-130686

NEWS

Google and Facebook shouldn't subsidise journalism, but the government could

Jeff Chiu/APYou might have missed it – what with the biggest recession since the 1930s and a pandemic going on – but there may be big, and bad, changes happening...

COVID-19 has offered us an unexpected opportunity to help more people quit smoking

ShutterstockSmokers are worried. A respiratory disease is running rampant across the globe and people with unhealthy lifestyle habits appear to be especially vulnerable. We know smokers hospitalised with COVID-19 are...

who was Jeanne Barret, the first woman to circumnavigate the globe?

A modern portrait of Jeanne Barret disguised as a man, based on the author's interpretation.Timothy Ide, Author providedIn 1765, a young, peasant woman left a remote corner of rural France...

Greyhound pups must be tracked from birth to death, so we know how many are slaughtered

ShutterstockIt’s been more than four years since New South Wales greyhound racing was rocked by a special inquiry that found overwhelming evidence of systemic animal cruelty, including mass killings. Overbreeding...

We looked at 35 years of rainfall and learnt how droughts start in the Murray-Darling Basin

The extreme, recent drought has devastated many communities around the Murray-Darling Basin, but the processes driving drought are still not well understood. Our new study helps to change this. We...

As a second wave of COVID looms in the UK, Australia is watching closely

Aaron Chown/AAPThe United Kingdom has already been battered by COVID-19, with about 410,000 cases and more than 41,000 deaths.But after some respite over summer — and entreaties to “Eat Out...

Testamentary trusts are one of the last truly outrageous means of avoiding tax

Scott Graham/UpsplashIt’s one thing to bring forward tax cuts, as the government is thinking of doing in the October budget.It’s another to leave wide open an arrangement that allows substantial...

Can Morrison use his 'bully pulpit' to inspire the confidence vital for economic recovery?

We’ve all observed Scott Morrison’s pragmatism in this pandemic but COVID has highlighted another notable feature of his political style.The prime minister is a great admirer of Theodore (“Teddy”) Roosevelt...

Government proposes changes to smooth the path for borrowers

The government has announced reforms to facilitate an increased flow of credit to households and businesses.A key change will be that banks and other lenders will be able to rely...

Keating is right. The Reserve Bank should do more. It needs to aim for more inflation

Ashwin/ShutterstockFormer prime minister Paul Keating isn’t alone in wanting the Reserve Bank to do much more to ensure economic recovery.In an opinion piece for major newspapers he has said it...

COVID will leave Australia with smaller economy and older population: Frydenberg

Josh Frydenberg has painted a sombre picture of the outlook for the Australian economy, saying that by mid next year it is set to be 6% smaller than forecast at...

Expanding Victoria's police powers without robust, independent oversight is a dangerous idea

ERIK ANDERSON/AAPThe state of emergency that has been issued in Victoria during the pandemic is to be taken seriously. Police are undoubtedly one component of the state’s health response, needed...



News Company Media Core

Content & Technology Connecting Global Audiences

More Information - Less Opinion













Popular articles from Modern Australian

Fitness Tips: 3 Ways to Stay in Shape At HomeWear a Mask and protect yourself in StyleWellness expert:  Cutting up your fruit cuts the goodness out of themRegain Your Natural Smile Getting Porcelain Crowns in MelbourneIs Photography Still Important In 2020?Thinking of Hiring a Boat? Check these Facts FirstDo You Know that Certain Serious Athletic Injuries Can Turn into Medical Malpractice?Most In-Demand Suburbs for Property Buyers in Australia Post Covid-19What Is Selective High School?Optimise Your Diet with Multitasking Nutrients What to Look for When Buying a Table SawWhat To Consider When Choosing A Rifle Scope You Actually NeedHow to Find Water LeaksDownsizing to move house – tricks and trapsBest 2020 & 2021 Honeymoon Spots