Thursday, 30 January 2020

Forecasting the number of potential coronavirus cases




Chinese health authorities reported a group of cases of viral pneumonia to the World Health Organization (WHO) in late December 2019 and this new virus is now referred to as 2019-nCoV. The number of cases is almost eight thousand and is growing at an alarming rate of 40% per day. A total of 170 people have died as a result of the virus. The coronavirus appears to be contagious before symptoms appear with an incubation period of 10 to 14 days, making it incredibly difficult to identify cases. The number of cases reported by the National Health Commission in China and the WHO are crucial for facilitating decision-making about the virus.  A wikipedia website is dedicated to collecting the timeline statistics for the virus [1]. By plotting the number of confirmed cases it is apparent by eye that the numbers are growing exponentially which is demonstrated by the straight line on the above log-scale chart. If the virus maintains this trajectory, the number of cases could surpass 100,000 by 04-Feb-2020. While this projection demonstrates its potential based on the existing cases, it is expected that a coordinated response will reduce the rate and eventually prevent the progression of the virus. There is no doubt that the situation will likely get worse before the virus is brought under control.

Investigations suggested that the source of the virus is a seafood and animal market in Wuhan, a large city with eleven million inhabitants in eastern China. It was initially believed that people were at risk due to exposure to animal markets, but later developments and the dramatic increase in confirmed cases clearly demonstrates that person-to-person infection is occurring. China has announced the virus can be spread by touching and contact and it is likely that it could also be spread via fine, airborne particles, which are inhaled into the lungs of the recipient [2].

On 23-Jan-2020, the WHO Director-General Tedros Adhanom Ghebreyesus stated “This is an emergency in China, but it is not yet a global health emergency”. Apparently the WHO emergency meeting struggled to reach a decision, explaining that at that time all the deaths, and 575 of the 584 reported illnesses, took place in China.

The response to the threat of the virus has been considerable, especially within China.  The Chinese President, Xi Jinping, told the head of the WHO on 28-Jan-2020 that the new coronavirus is a “devil” and that China is confident of winning the battle against it. China has has issued the largest quarantine in human history with 16 cities in lockdown (approximately 46 million people) in an attempt to contain the virus.  Cases have now been confirmed in 19 countries outside mainland China, including those as far away as the US, Canada, France, Germany and Australia. In recognition of the severity of the situation, the US, UK, European Union and Australia are airlifting their citizens from the city of Wuhan.

On 29-Jan-2020, the WHO announced that the "whole world must take action" and Tedros Adhanom Ghebreyesus, added that the WHO "deeply regrets" referring to the worldwide risk from the virus as "moderate" in three reports last week instead of "high" [3].  The initial decision by the WHO on 23-Jan-2020 to not declare 2019-nCoV a global health emergency seems to have ignored the obvious and alarming trend and demonstrated a remarkable level of optimism that the virus could be managed and contained within China.

The 2019-nCoV virus has a mortality rate of approximately 2% based on confirmed cases making it less deadly in comparison to two previous epidemics. The 2002/03 SARS outbreak (Severe Acute Respiratory Syndrome) started in Guangdong Province of China and killed 774 people out of a total 8,096 infected [4]. The 2012 MERS outbreak (Middle East respiratory syndrome) killed 858 people out of the 2,494 infected [5]. These numbers imply mortality rates of 9.6% and 34.4% for SARA and MERS respectively.

Seasonal flu typically kills 290,000 to 650,000 people per year, according to the WHO [6]. Two-thirds (67%) of seasonal influenza deaths occurred in those greater than or equal to 65 years of age [7]. Unlike seasonal flu, however, there is no vaccine for the new coronavirus, which means that vulnerable members of the population are at risk. Chinese officials have already released the genetic code of the virus,  which will enable scientists to identify its origin, understand potential mutations and most importantly how to protect people against it. While research is underway, estimates for the time taken to obtain a vaccine range from several months to a year. 

Given the concerning increase in confirmed cases, it is important to acknowledge the substantial risk posed by this new coronavirus. History provides some chilling evidence of previous pandemics. In the 20th century, three influenza pandemics occurred: Spanish influenza in 1918 (40–50 million deaths), Asian influenza in 1957 (two million deaths), and Hong Kong influenza in 1968 (one million deaths) [8]. Surely the risk of an emerging pandemic is enough to warrant concerted action. It may finally be time for the WHO to recognise this virus as a high worldwide threat and start coordinating a rapid global response.

References
[1] Timeline of the Wuhan coronavirus outbreak, Wikipedia. 
[2] How contagious is the Wuhan coronavirus and can you spread it before symptoms start? The Conversation 28-Jan-2020.
[3] Coronavirus: Whole world 'must take action', warns WHO. BBC News 28-Jan-2020.
[4] Severe Acute Respiratory Syndrome (SARS), World Health Organization. 
[5] Middle East Respiratory Syndrome (MERS), World Health Organization.
[6] Influenza (Seasonal),World Health Organization.
[7] Global mortality associated with seasonal influenza epidemics: New burden estimates and predictors from the GLaMOR Project. J Glob Health. 2019 Dec; 9(2): 020421.
[8] Influenza, Wikipedia.

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