When preparing for the possible sustained transmission of the novel 2019 coronavirus (2019-nCoV), both public health officials and physicians alike would benefit from looking to the past. In a viewpoint article published in JAMA, David L. Swerdlow, MD, and Lyn Finelli, DrPh, highlighted 3 previous viruses that caused pandemic conditions: the 2009 pandemic influenza A(H1N1) virus (also known as swine flu), the severe acute respiratory syndrome coronavirus (SARS), and the Middle East respiratory syndrome coronavirus (MERS).
Though these viruses were all of public health concern, none had a combination of high transmissibility and high severity, which are the 2 most critical factors that affect the course of an epidemic. The basic reproduction number (R0), defined as the number of additional people that is infections by 1 person over the course of their illness, is used to measure the transmissibility of a virus. A value of R0 <1 is associated with a tapering pattern of infection, whereas a value >1 is linked to potential sustained transmission.
The influenza A(H1N1) virus that caused the swine flu pandemic, which originated in the United States in 2009, had R0 values of 1.7 and was responsible for roughly 201,200 deaths across 120 countries. However, the illness was not as severe as the influenza pandemic of 1968 (30-times higher mortality rate), or the 1918 pandemic (1000-times higher mortality rate).
Conversely, the SARS and MERS pandemics of 2003 and 2012 to the present, respectively, cause severe disease states. However, these infections were not as transmissible as initial concerns suggested. Initial R0 values were >2.0, which is indicative of near certain global transmission; however, there were a total of 8098 reported cases, and 774 deaths in 37 countries that were associated with SARS. This demonstrated a case-fatality rate of 9.6%. The article articles highlight the rapidly severe course of illness as the cause of this low transmissibility because it allow simply and quick recognition and isolation of individuals with the infection.
The course of the MERS pandemic has proven similar to SARS. Since 2012, there have been 2494 cases of MERS and 858 deaths across 27 countries related to the infection. This is a case-fatality rate of 34%, but an R0 score of <1.
Although it is not yet possible to determine the trajectory of the 2019-nCoV, the medical community can look to previous preparedness plans to develop current guidance. For example, the United States Department of Health and Human Services’ Pandemic Influenza Plan incorporates a combination of pharmaceutical and nonpharmaceutical interventions, including school closings and antiviral prophylaxis, to interrupt and slow influenza transmission. When MERS emerged in the Middle East, preparedness plans included a surveillance plan, laboratory testing, and contact tracing guidance, as well as infection control guidance developed for public use.
Despite these preparations, Swerdlow and Finelli questioned whether the world is ready for a respiratory virus that is both highly transmissible and highly severe. They cited a series of modeling articles published after the identification of influenza virus H7N9 in China in 2013. Presented scenarios used clinical attack rates of 20% to 30% to estimate a severity of 669,000 to 4.3 million hospitalizations and 54,000 to 538,000 deaths.
“The scope, morbidity, and mortality [of the 2019-nCoV] will depend on the combination of severity and transmissibility,” the article authors wrote. A combination of “nowcasting” how many cases have already occurred and forecasting how many cases are likely suggests that rapid person-to-person transmission is possible.
Disease modelers have estimated the R0 to be 2.2 for 2019-nCoV. A statistic from the University of Hong Kong estimates that the outbreak may affect upwards of 150,000 people per day in China at its peak. In terms of severity, 14% of 2019-nCoV cases have been described by the World Health Organization as severe; the case-fatality rate is currently 2.1%, although this may be an underestimation.
“In preparing for possible sustained transmission of 2019-nCoV beyond China, applicable lessons from previous experiences with epidemics/pandemics of respiratory viruses should be carefully considered to better control and mitigate potential consequences,” Drs Swerdlow and Finelli concluded. “Countries have been successful in the past, and there is nothing yet to predict that this time it is likely to be worse.”
Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Swerdlow DL, Finelli L. Preparation for possible sustained transmission of 2019 Novel Coronavirus: Lessons from previous epidemics [published online February 11, 2020]. JAMA. doi:10.1001/jama.2020.1960