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27 Feb 2020

A 101 on the novel coronavirus

What is a coronavirus?

Coronaviruses are family of viruses that infect people and a wide range of animals. Human coronaviruses generally cause a mild illness like the common cold. When animal coronaviruses infect humans, they can cause severe disease. This happened in 2002/2003 with severe acute respiratory syndrome (SARS) and since 2012 with Middle East Respiratory Syndrome (MERS). The latest coronavirus infection, now officially named COVID-19, is considered novel as it had never been identified prior to December 2019.

What do we know (and not know) about this new virus?

How is the virus transmitted? How long is the virus incubation period? Can someone not showing symptoms pass on the infection? How contagious is it? What is the mortality rate? We need accurate answers to predict how the outbreak will progress and determine effective prevention measures.

There has been an increasingly rapid stream of information becoming accessible online at an unprecedented rate, providing a description of this emerging epidemic in real-time. The first patients were reported in Wuhan in December 2019 as having pneumonia of unknown cause.  Several days later, Chinese researchers identified the causative agent: a novel coronavirus strain. Now there is global collaboration as researchers investigating this outbreak share their work rapidly and openly.

However, many key questions for mapping the outbreak remain unanswered due to an information delay. There is a significant time lag from an individual becoming infected, to then becoming symptomatic, to seeking care and being tested and reported. In mid-January, there were still only 41 laboratory-confirmed cases, and now there are over 18,445,787 confirmed cases.

New diagnoses will always precede recovery (or death) by days to weeks and what we see in real time is merely the tip of the iceberg.

How dangerous is it and who is most at risk of catching it?

COVID-19 causes respiratory illness with most cases reporting mild symptoms similar to the common cold or flu. A proportion of people, especially older people and people with pre-existing medical conditions develop severe pneumonia, and over 697,998 people have died. Surprisingly, for unknown reasons, younger people appear to be more protected, which is similar to a trend observed during the 2003 SARS epidemic.

There have been a total of 18,733 cases of COVID-19 infection in Australia to date, and 232 confirmed deaths. Worldwide, out of 18,445,787 confirmed cases there have been 697,998 deaths.

The true case-fatality rate is still being assessed due to variation in reporting between countries and the lag time between diagnosis and death/recovery. There is likely an underestimation of the total number of cases, as the bulk of COVID-19 infections might remain largely unrecognised, compounded with the skewing of case fatality estimates towards patients presenting with more severe disease who seek medical attention. It is clear, however, that number of deaths is rising every day.

How long is it between catching it and getting sick?

It is essential to know the incubation period, the time between initial infection and onset of symptoms, to determine the appropriate duration of quarantine. Emerging data estimate the incubation period to be around 6.4 days, ranging from 2-11 days.  This long incubation period means that people can be unaware that they are sick for about a week, and there have been multiple reported cases of people transmitting the virus prior to the onset of symptoms.

Airport screening is also being used to identify infected travellers to limit the spread between countries, as was done during the 2003 SARS epidemic and 2009 H1N1 influenza A (Swine Flu) pandemic. Thermal testing is currently being used to identify passengers with fever before boarding flights, however the rate of transmissible infections from asymptomatic travellers have to be considered. A new study predicted that 46% of infected travellers will board planes with undetected infections, therefore limiting the effectiveness of airport screening and risking spread to other passengers and diverse locations.

How is the virus transmitted?

It is likely that the virus was initially transmitted to humans from bats, as there is increasing evidence that demonstrates a link between the COVID-19 and similar coronaviruses circulating in bats. How the jump occurred remains unclear, but the infection may have occurred directly from bats or through an unknown intermediary animal.

The mode of human-to-human transmission also remains unknown. During previous coronavirus outbreaks, human-to-human transmission occurred through droplets, contact and contaminated objects. The transmission mode of the COVID-19 may be similar and the World Health Organization (WHO) infection prevention and control guidelines are based on this.

Are there any medications to prevent or treat COVID-19?

As COVID-19 is a virus, antibiotics have no effect in treating infection. Researchers are currently exploring existing antiviral drugs that are used in HIV and Ebola infection for their effectiveness against COVID-19.

Clinicians have jumped straight to clinical trials in the face of an outbreak, similar to the fast-tracking of access to experimental Ebola drugs in 2014. It also may be possible to design a drug that will block the ability of the virus to infect human respiratory cells, similar to the design of Relenza and other drugs used to treat influenza.

Do masks provide any protection?

Masks can help limit the spread of respiratory viruses that are transmitted by droplets from an infected person’s cough or sneeze. However, given that the mode of transmission for COVID-19 has not yet been confirmed, wearing a mask is not guaranteed to keep you safe.

The WHO advises on the rational use of medical masks to avoid wastage of precious resources. News reports suggest that masks have sold out in stores across Asia and supermarket aisles are bare as people panic-buy and stock-pile items.

Australia had already depleted its supply of P2 masks before COVID-19 officially reached Public Health Emergency status. These masks filter fine air pollutant particles and have been used as protection against the severe smoke haze caused by bushfires. Another type of protective mask is the surgical mask, worn by medical staff to prevent transmission of diseases by exposure to large droplets from patients. Individuals experiencing cold- or flu-like symptoms and healthcare workers are therefore encouraged to wear surgical masks to reduce the likelihood of spread, but Australian health authorities do not recommend masks for the general population.

How is Australia/Melbourne going to be affected by the outbreak?

The virus is highly contagious and infectious. Epidemiologists measure contagiousness by defining a reproductive number (R0), that is, the number of people an infected person transmits to. Early models indicated an R0 of 2.2, but a more recent estimate claimed 4.7-6.6, meaning that each infected person spreads the infection to around 5 either people. Notably, this value is for the situation in Wuhan and the spread of virus in Australia may be lower given our preparedness.

Mathematical models suggest that the outbreak will peak in Wuhan in mid-late February, however, we simply do not have enough information to accurately predict and map the COVID-19 outbreak and how it will affect us here.

How is the Doherty Institute involved in controlling the outbreak?

The Victorian Infectious Diseases Reference Laboratory (VIDRL), located at the Doherty Institute, had an existing pan-coronavirus PCR assay, a method of detecting the presence of viral DNA in a person to confirm infection, and it was simply a matter of adapting it to aid in COVID-19 detection and diagnosis. VIDRL has also maintained the ability to recover viruses in culture, a technique that many laboratories around the world have discontinued.

On 24 January, the first COVID-19 case was diagnosed in Melbourne. The VIDRL team isolated the virus from this patient in cultured cells. By 28 January, they had successfully grown and isolated the virus and shared it with public health laboratories around the world as well as the WHO  – the first time this had been done outside of China. This allowed the team to sequence the full genome of the virus and share the information worldwide to aid in diagnosis and treatment development. Australian researchers, including those at the Doherty Institute, are now playing a role in vaccine development with the new information obtained from the lab-grown virus.

*This outbreak is ongoing and some of the information eg R0, number of cases, severe cases, deaths and recovered cases will change.

The information above is correct as of 27 February, 2020.

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