Question

1. SARS emerged in 2003, spread to 26 countries with more than 8000 cases (WHO) with a case fatality rate (CFR – the death rate) of 11%. MERS emerged in 2012 and had a CFR of 35%. It is very difficult to estimate the CFR of COVID-19 worldwide, and CFRs will differ in different countries (due to health systems, and underlying population demographics), but ranges seem to be between 0.5% and 3%. Why is SARS-CoV-2 more dangerous than SARS-CoV-1 or MERS given it has a lower death rate? (~300 words, include a short reference list)

Answer 1

The coronavirus SARS-CoV-2 is the pathogen that causes COVID-19. Even though it has a lower death rate of 0.5% to 3%,

SARS-CoV2 is a novel coronavirus identified as the cause of coronavirus disease 2019 (COVID-19) that began in Wuhan, China in late 2019 and spread worldwide.

MERS-CoV was identified in 2012 as the cause of Middle East respiratory syndrome (MERS).

SARS-CoV was identified in 2003 as the cause of an outbreak of severe acute respiratory syndrome (SARS) that began in China near the end of 2002.

COVID-19 summary, as of April 9, 2020:

• Pathogen: SARS-CoV-2
• Total number of cases: 1,490,790
• Number of cases in the U.S.: 432,438
• Total number of deaths: 88,982
• Case fatality rate: 1.38% to 3.4%
• Mode of transmission: Droplets produced by coughing, sneezing, or talking, limited evidence of other routes
• Mean incubation period: 5 days
• Key symptoms: A fever, a dry cough, shortness of breath
• At-risk groups: Adults aged 65 and over, and people of all ages with underlying medical conditions
• Treatment: No specific treatment, although several candidate drugs are undergoing testing
• Vaccine: No vaccine, although several candidate vaccines are in development.

Despite the lower case fatality rate, the overall number of deaths from COVID-19 far outweighs that from SARS or MERS.

Early COVID-19 cases were linked to a live animal market in Wuhan, China, suggesting that the virus was initially transmitted from animals to humans. Person-to-person spread occurs through contact with infected secretions, mainly via contact with large respiratory droplets, but it could also occur via contact with a surface contaminated by respiratory droplets and possibly by aerosol transmission of small respiratory droplets. Researchers are still learning how readily this virus spreads from person to person. It is known that symptomatic, as well as asymptomatic and presymptomatic patients, can transmit the virus. The virus appears more transmissible than SARS.

Super-spreaders played an extraordinary role in driving the 2003 SARS outbreak and may also play a significant role in the current COVID-19 outbreak and estimates of transmissibility. A super-spreader is an individual who transmits an infection to a significantly greater number of other people than the average infected person. Persons with minimal or no symptoms may also be able to transmit disease, making it difficult to control the outbreak.

Situations with high risk of transmission include facilities such as nursing homes, long-term care facilities, prisons, and on board ships. Such situations involve high population density and often difficulty in maintaining avoidance precautions. The residents of nursing homes are also at high risk because of age and underlying medical disorders.

Reference

1. Severe Acute Respiratory Syndrome Coronavirus as an Agent of Emerging and Reemerging Infection Clin Microbiol Rev. 2007 Oct; 20(4): 660–694.

2. Pathology and Pathogenesis of Severe Acute Respiratory Syndrome Am J Pathol. 2007 Apr; 170(4): 1136–1147.