[PLEASE NOTE: This is an article from the early stages of our understanding of Covid-19 and our knowledge and understanding has since been updated and refined since it was originally published]
This is what we do and don’t know about the Wuhan coronavirus spreading around the world.
A fact-based approach to information about the current pandemic, suitable to support delivery of the Year 8, 9 and Senior Secondary National Curriculum for Biological Sciences.
For definitions of epidemic, pandemic and other terms useful for this topic please direct your students to https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section11.html
Word Count: 1395
Why This Matters: Investigations around the world are still piecing together the puzzle.
As the number of confirmed cases of the Wuhan coronavirus, properly named 2019-nCOV, in Australia hits five, experts are beginning to understand more about the outbreak and virus itself.
However, there are still many questions that don’t have answers. Here is what we know, and don’t know, already.
What is a coronavirus?
Coronaviruses are a group of viruses which cause infections of the respiratory system. While they’re a large family of viruses that are common in many different species of animals, including camels, cattle, cats, and bats, they rarely spill-over into humans.
There are 7 known coronaviruses that can infect humans, which include the cause of the current outbreak 2019-nCOV which emerged in Wuhan, China; SARS (Severe acute respiratory syndrome), which emerged in 2002 in Asia and killed 774 people; and MERS (Middle East respiratory syndrome) which first appeared in humans in 2012 and has killed 858 people mostly on the Arabian Peninsula.
The viruses themselves are covered with spikes which help it bind to cells in the host. Once bound, the virus infects the cell and hijacks the cell’s own machinery to replicate the virus, which are then released to infect other cells.
How many people are infected?
The majority of those infected have been within China, however at least 44 cases have been identified in 17 other countries.
So far there have been 5 confirmed cases in Australia, four in NSW and one in Victoria. There have been no deaths outside of China.
“Knowing what’s happened in other countries and knowing the traffic from that part of China to Australia, it’s highly likely we may see some more,” says Australia’s Chief Medical Officer Brendan Murphy.
How does it spread?
The initial cases of 2019-nCOV were traced to a live food market in Wuhan, which points to an animal-to-human transmission. The genetic sequence of virus samples from patients in the US were similar to that from Chinese patients, which suggests the virus recently emerged from a single animal source, according to the CDC.
Some early research compared similarities in the genetic code of the virus with species known to be sold in the market suggested the animal source may have been snakes, however more recent research has refuted that, suggesting instead the closest similarities were with bats. In another study published on the pre-print site biorxiv, scientists compared the genetic code of the virus with the coronavirus that caused SARS, and other bat coronaviruses. They found the new virus shared 80% of its genes with SARS and 96% of its genes with bat coronaviruses. However, further research will continue to confirm the animal origin of 2019-nCOV.
The recent spread has shown that the virus is capable of spreading from human-to-human. It it thought to spread from droplets sprayed when someone coughs or sneezes, similar to how influenza and colds spread. According to Raina McIntyre, who heads up the Kirby Institute’s Biosecurity Research Program, these droplets can hover around in airborne particles for hours.
“The focus in Australia should be on detecting new cases as soon as possible and isolating them, and preventing hospital outbreaks. Protecting our health workers is a high priority,” she says.
How infectious is it?
How easily a virus spreads person-to-person can vary. This transmissibility is one question that is still yet to be understood.
Some epidemiological studies have been narrowing in on the R0, a mathematical measure of how transmissible an infectious disease is. While most studies are suggesting an R0 of around 2.5 or more – meaning on average one person would infect at least another 2.5 people, the ranges across the studies stretch from 1.5 to 4 using different models and as reported numbers of infected change. This is similar to SARS, which initially had an R0 of 2.9, however dropped to 0.4 after control measures were put in place. (The most infectious virus is measles, with an R0 of 18.)
One big difference of the latest outbreak has been the speed of the spread. SARS took almost 5 months to spread to 3,000 people. 2019-nCOV has taken just 28 days.
After the confirmation of cases in NSW of people who travelled from Wuhan, NSW Chief Medical Officer Kerry Chant stated, “We do not believe that they were infectious at the time of their international flight.” It’s likely that statement was made based on the experience of SARS, when the risk of transmission was highest five to ten days into the illness. However, given the lack of knowledge around transmission and the virus life cycle of 2019-nCOV, it’s still unknown whether this virus shares those characteristics. Chinese officials have stated that the virus may be infectious before symptoms appear.
Despite this global spread the World Health Organisation has not declared the outbreak to be a global crisis. “Make no mistake. This is an emergency in China, but it has not yet become a global health emergency,” said WHO Director General Tedros Adhanom Ghebreyesus.
How deadly is it?
On the numbers that are available (as of Tuesday 28 January 2020), the mortality rate for 2019 nCOV is around 2.4%. That is far lower than many other coronavirus outbreaks, such as SARS which had a mortality rate of nearly 10%, and MERS which is around 35%.
However, the risk is higher for health workers, and people already in hospital, says McIntyre.
“During SARS, many health workers died, and 21% of all cases of SARS were in health workers. While the overall fatality rate is 2-5%, the fatality rate in hospitalised patients is 15% and higher in patients admitted to ICU.”
It’s always possible those numbers could change, or the virus mutates into a more fatal form. Recent surges in case numbers may have reflected a rise in infections, or increased testing and reporting.
“The genetic data we have seen does not suggest it is mutating rapidly,” says McIntyre.
What are the symptoms?
So far the symptoms reported commonly include fever, dry cough, fatigue or muscle pain and breathing difficulties. Less common symptoms reported include coughing up mucus or blood, headaches and diarrhea. The infection can then progress to pneumonia, where the lung become inflamed and fill with fluid.
Those symptoms can appear as few as 2 days or as long as 14 after exposure, according to the CDC. This estimate is based on what has been seen previously as the incubation period of MERS viruses.
“There is everything from the worried well to people who are desperately ill and have to be admitted to intensive care units. So clearly there is a spectrum of severity.”
What is the treatment?
“There is no recognised therapeutic against coronaviruses,” the WHO’s Health Emergencies Programme executive director Mike Ryan told a press conference last week.
“The primary objective in an outbreak related to a coronavirus is to give adequate support of care to patients, particularly in terms of respiratory support and multi-organ support.”
“The team hopes to develop a vaccine over the next six months, which may be used to help contain this outbreak,” says UQ’s Paul Young.
“The vaccine would be distributed to first responders, helping to contain the virus from spreading around the world.”
What can we do to protect ourselves?
As always, the best plan is to avoid infection.
The WHO encourages similar measures as you might take to avoid the flu – practice good hand hygiene, cover your mouth and nose when sneezing, and avoid people with flu-like symptoms. In addition, obviously, avoid travelling to areas with outbreaks.
If you do feel unwell, you should seek medical attention, but also take actions to avoid infecting others such as wearing a mask and staying away from others as much as possible.
“Potential patients have been advised to call ahead before going to the GP, and that in NSW, GPs have been advised to immediately contact their public health unit if a patient contacts them,” says Raina.
If you think you may have been infected with coronavirus, phone your GP or health clinic before visiting.
For more information contact the Public Health Information Line on 1800 044 599.
More information is also available at the Australian Government Department of Health website: health.gov.au/news/novel-coronavirus-2019-ncov
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