Latest on coronavirus transmission

By June 28, 2020Science, Society

Renyi Zhang, from Texas A&M University, and colleagues have published a paper (June 11) in the Proceedings of the National Academy of Sciences of the USA in which they determine the dominant method of transmission of Covid-19. They analysed trends and mitigation measures from January 23 to May 9 in three epicentres (Wuhan, Italy and New York City). Covid-19 broke out in Wuhan in December 2019. The numbers of confirmed infections and fatalities in China dominated the global trend during January and February 2020, but in China these have declined sharply since February. The epicentre shifted from Wuhan to Italy in early March and to New York City (NYC) in early April. By April 30, the numbers of confirmed Covid-19 cases and deaths, respectively, reached over 200,000 and 27,000 in Italy and over 1,000,000 and 52,000 in the United States, compared to about 84,000 and 4,600 in China. The cases and fatality curves in Italy have slowed since mid-April, while the numbers in the world and the United States continue to increase. At the time of writing of this article (June 28), China was still getting about 20 new cases per day (total cases 84,726; deaths, 4,641); Italy about 175 new cases per day (total cases 240,136; deaths 34,716); and the USA about 40,000 new cases a day (total cases 2,590,282; deaths 128,108). Globally, the number of cases has now passed 10 million, with a daily increase of nearly 200,000, while the number of deaths has now passed 500,000, and is increasing at over 4,000 per day2,3.

Zhang and colleagues analysed the trend and mitigation measures in the three epicentres. Their results showed that the airborne transmission route is highly virulent and is the dominant mode of spread for Covid-19. They were able to discern the most effective mitigation measures from the trends of the pandemic in the various epicentres. Their analysis has shown that the use of a face mask is the dominant factor in shaping the trends of the pandemic. It is the single protective measure that has most significantly reduced the number of infections. Other mitigation measures, such as social distancing, implemented in the United States and in many other places, including Australia, were insufficient by themselves in protecting the public. Their work has also demonstrated that sound science is essential in decision-making for the current and future public health pandemics1. It is also important that we learn from what worked this time around, ready for the next one, which will come. Taiwan learned this in 2003.

Taiwan suffered 346 cases and 73 deaths from the SARS virus in 2003 which, being of the coronavirus family and closely related to the virus that causes Covid-19, is transmitted much the same way; by airborne droplets from coughing, sneezing or talking. As a consequence, when Covid-19 raised its ugly head, Taiwan struck hard and struck early, and started shutting down travel in December 2019, before it had its first confirmed case. Australia didn’t start doing that sort of thing until much later4. In addition, Taiwan’s relatively low COVID-19 transmission rate is attributed to the fact that a majority of people in the country wore face masks in public5. In Australia only a very small minority of people have worn face masks in public. Wearing a face mask may not necessarily prevent you from contracting the virus (although it is 70% effective), but it is even more likely stop you from transmitting it5. One factor which also had an impact in Australia, as in the USA, was the cultural aversion to wearing face masks. As a consequence, Taiwan, in which wearing masks is not uncommon in ‘normal’ times, and which has a similar population to Australia, had only had 447 cases and 7 deaths from Covid-19, while Australia has had 7,641 cases and 104 deaths2. The ‘she’ll be right’ or ‘I’m alright, jack’ attitude may be our enemy. We should learn from other countries’ successes and not have to learn from our own mistakes again and again. People’s lives depend on it.



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