23 Jan 2020
Kylie Carville: Virus threat drops when we get preparation right (Herald Sun)
A nervous world is watching as a new virus spreads out of China but Australia can cut the risk of exposure if governments prepare properly, writes Royal Melbourne Hospital epidemiologist Kylie Carville from the Doherty Institute.
This is an exerpt from an article that first appeared in the Herald Sun.
AFTER the SARS and MERS viruses we are now seeing headlines about “2019-nCoV”. But what does this mean at home and for those travelling overseas? Where do these new viruses come from and how worried should we be?
Viruses from the coronavirus family cause respiratory illnesses: colds or flus. But those viruses also circulate in animals and an animal virus may change enough, or mix with a human version, to be able to infect us.
It’s estimated that 60-80 per cent of new viruses in humans come from animals. SARS was linked to civet cats in live animal markets, although the primary reservoir is bats. MERS was linked to camels and camel products. The first cases of 2019-nCoV have been linked to a seafood market in Wuhan, China, that also sells live animals.
The risk we face from a new respiratory virus depends on the virus and our response. The key viral characteristics are how well it spreads and how sick it makes people. If it spreads easily but doesn’t cause severe illness, it’s not a problem, even if it spreads globally and becomes pandemic.
If it causes severe illness but is not easily transmissible, it’s a concern to residents and travellers in the region in which it emerged, but it’s unlikely to become pandemic.
When a new virus transmits reasonably effectively and also causes severe illness, there is potential for a damaging pandemic.
It takes time to determine those characteristics after a new virus emerges, so there will be global monitoring of the situation. Through the International Health Regulations, countries have agreed to notify the World Health Organisation of “an event that may constitute a public health emergency of international concern”. Global awareness means countries can prepare.
Chinese authorities reported 2019 n-CoV less than a month ago. We know there has been some person-to-person transmission and cases have been reported from at least five countries. But we don’t know how easily the virus can be transmitted between people. Early indications from limited data are that it does not seem as clinically severe as MERS (case fatality rate of 35 per cent, compared with 11 per cent for SARS), nor possibly as transmissible. Understanding will evolve as experience accumulates. It is thought to take about a week from infection to signs of illness, but we don’t know how long someone is infectious, whether there are asymptomatic infections and whether some types of people are more likely to become severely ill.
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