global response

Explainer: Here's what we know so far about how Covid-19 is spreading

Where did the new coronavirus Covid-19 come from, and what does it want?

shutterstock_1626897328 A 3D medical illustration of the coronavirus 2019-NCoV infection. Shutterstock / Corona Borealis Studio Shutterstock / Corona Borealis Studio / Corona Borealis Studio

HOW IS THE new coronavirus Covid-19 spreading?

There’s been an increased focus on the new coronavirus in recent days after the number of confirmed cases in Italy soared to over 350 over the weekend.

This has led to the Irish government requesting that the Ireland-Italy Six Nations match scheduled for 7 March in Dublin to be called off, and concern among parents whose children had attended skiing holidays in Italy recently.

The fact of the matter is, there’s a lot we don’t know about Covid-19, which is precisely why the global community is taking significant measures to contain the virus. 

The World Health Organization (WHO) is a specialised agency of the United Nations that is concerned with world public health. On 11 February, WHO chief Tedros Adhanom Ghebreyesus said that the key question in the battle against the novel coronavirus is how quickly it is spreading beyond China.

“The detection of a small number of cases [outside of China] may indicate more widespread transmission in other countries; in short, we may only be seeing the tip of the iceberg,” he warned.

Now, countries outside China are reporting more new cases than China itself. Confirmed cases currently stand at over 81,000 (78,000 of these in China), with 2,762 deaths (2,715 of these in China). Over 30,000 people have recovered from the virus.

  • You can view a map of where cases have been confirmed here.

Here’s what we know so far about how the virus is spreading.

Where did it come from?

Covid-19 broke out at a seafood and live animal market in Wuhan, a province in China, on 31 December 2019.

As with SARS (Severe acute respiratory syndrome-related coronavirus) and MERS (Middle-East respiratory syndrome-related coronavirus), the virus is thought to have originally been shed by bats, passed onto an intermediary animal, and was then passed onto humans.

With SARS the intermediary animal was cats, and with MERS the intermediary animal was a camel. The death rate for those coronaviruses was 9.5% and 34.5% respectively.

World Health Organization (WHO) / YouTube

The coronavirus is a family of viruses which includes the common cold and the flu – it’s given its name because of the crown shape on the molecule.

The strain at the centre of this outbreak is called Covid-19, (or 2019-NCoV) and is a respiratory virus (some coronaviruses can cause gastrointestinal symptoms).

How does it spread?

It is thought that it spreads through specific contact with an infected person: if their coughs, sneezes, droplets of saliva or other body fluids are passed onto another person through their eyes, mouth or nose.

Scientists have deduced from what we know so far that a person needs to be within a metre of an infected person to risk catching it – as that’s the zone where bodily fluids can be projected through a cough or sneeze. The virus can’t get through skin.

It can only last on surfaces for a limited time – if the area the coronavirus is on is exposed to direct sunlight, it won’t last as long as it would in darkness.

Very simple precautionary measures can lower your risk from contracting Covid-19 and other coronaviruses, including:

  • Washing your hands frequently and properly
  • Coughing or sneezing into a tissue
  • Coughing into your elbow or away from other people if you don’t have a tissue.

If you are infected, wearing a mask can protect others. / YouTube

Dr Cillian De Gascun, the chair of the HSE’s Coronavirus Expert Advisory Group, said that “at this point in time, there’s no indication for people to wear a face mask”.

The group is a part of the National Public Health Emergency Team, which assesses Ireland’s preparedness and makes recommendations of actions it should take. Speaking to today, De Gascun said:

Hand sanitiser is important, but that’s important as a general means of protecting ourselves against infection. So realistically, if we practice good hand hygiene and good respiratory etiquette, then we will protect ourselves from the majority of respiratory virus infections.

How does the spread of Covid-19 compare to that of other viruses?

SARS, another coronavirus, infected 8,000 people over eight months. Covid-19 has infected at least 80,000 people in two months.

“That’s quite concerning, that’s why we need to take it seriously because it has become transmissible quite quickly,” De Gascun said.

From the cases identified so far, it’s suggested that every infected person passes on the virus to an average of 2.2 other individuals. This is known as the reproductive number.

That is a higher rate than the winter flu (1.3), lower than an infectious disease such as the measles (more than 12), and comparable to SARS (3).

What does Covid-19 ‘want’?

The first cases of human viruses tend to be the most deadly; the death rate eases off as the virus spreads, because the virus is looking for something or someone to live in, and it can’t do that if it kills its host. 

The virus begins to multiply in a person’s lower respiratory tract, which is why those who are infected develop a fever and cough early on. Most people will recover within a few days – over 30,000 people in China have recovered from the virus.

When does a person become infectious?

Identifying when an infected person becomes infectious, or when they pass on the virus to other people, is crucial in containing and managing the spread of a virus.

We don’t exactly know how long it takes for an infected person to be infectious, or whether an infected person can pass on the virus before they show symptoms.

Scientists initially thought the virus became contagious several days after symptoms started to appear, as happened with SARS. They now think it could be infectious earlier than that.

Close contact seems to be spreading Covid-19

upi-20200219 Staff prepare to help passengers testing negative for the Coronavirus disembark from the Diamond Princess at the Daikoku Pier in Yokohama. UPI / PA Images UPI / PA Images / PA Images

The Diamond Princess, is a cruise ship that has been docked off a pier in Yokohama, has been in since early February after a former passenger who got off the boat in Hong Kong had tested positive for the virus.

Despite the quarantine, the number of people aboard the ship has risen to 691. Passengers began leaving the ship after the quarantine method was criticised for failing to stop the spread of the virus.

“We’re seeing many countries with imported cases, it hasn’t managed to sustain transmission. So it’s really only close household contacts, obviously healthcare workers are affected,” De Gascun says. 

The natural experiment on the Diamond Princess demonstrates that given the correct circumstances, the virus can infect a large number of people quite quickly. 
We’re not seeing airplanes coming over with half the plane sick. Individuals are flying home, but they’re not infecting the whole airplane. 

“So, is casual contact sufficient? Possibly not?”

“What we’re looking at and trying to learn from is the transmission clusters that are well described – so the guy in the UK who was in France, the cases in Germany that had the link in Singapore, where we can map out the transmission dynamics quite well.

“But the problem is they’re small numbers by definition so are they the norm or are they the exception?”

How prepared is Ireland to stop it spreading? / YouTube

“We’ve been trying to get the balance right between the appropriate preparedness, but also without causing local panic,” says De Gascun. 

“At the moment, this remains a significant public health emergency for China,” he told last week, before Italy was added to the list of affected regions.

De Gascun said that up until this point, Ireland had been at “quite a low risk” because there are no direct flights between Ireland and China at this time of year. 

“Part of the reason the virus has been contained as much as it has is he fact that China has implemented such incredible containment measures, such as closing airports canceling public transport, you know, restricting public gatherings.

So what that did was give other countries, time to prepare and plan and put measures in place like we have in Ireland.

Currently, Ireland is at the early-detection/ containment phase of preparations. Because of this, screenings at ports and airports is viewed as unnecessary at this point. 

Coronavirus HSE HSE

“What we’ve learned from Berlin, London, and Singapore initially,” De Gascun says, “was that those imported cases didn’t necessarily need to give rise to sustained human-to-human transmission or standard well practiced infection prevention control procedures could contain it quite readily.”

De Gascun said that because China are “firefighting”, it was “really difficult” to tease out a pattern of how the virus is being transmitted.

“When you’re dealing with [over 80,000 cases and up to 3,000 deaths], it’s very difficult trying to figure out: when does this person become infectious, when did that person get exposed. So that’s the thing we’re still trying to figure out.”

You can find advice from the HSE on the new coronavirus Covid-19 here

With reporting from Nicky Ryan.

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