Table 3.

Examples of emerging human respiratory viral diseases without sustained human-to-human transmission

Virus	Originating animal host	Characteristics	No. of cases; CFR
SARS-CoV	Bat	First emerged in China in November 2002.76 Causes severe acute respiratory syndrome (SARS). Transmission through superspreading events in healthcare facilities.77	8422 cases; CFR:10%78
MERS-CoV	Bat	First emerged in the Middle East in 2012.79 Causes Middle East respiratory syndrome (MERS). Outbreaks from 2012 to 2019 in Saudi Arabia and one outbreak in South Korea (2015).	2502 cases; CFR: 34%79
Avian influenza A (H5N1 and H7N9)	Birds/poultry	Subtypes of influenza viruses detected in birds (having killed millions of poultry) but with ‘pandemic potential’ (WHO).80 H5N1 first detected in humans in 1997 in China with widespread emergence in 2003–2004; no sustained community-level transmission.80 H7N9 first detected in humans in China in 2013.81	H5N1: 649 cases; CFR: 60%82  H7N9: 571 cases; CFR: 37%81
Ebola virus	Bat	First appeared in 1976 and caused over 20 documented ‘major’ outbreaks.83 Largest epidemics in 2014–2016 in Guinea, Liberia and Sierra Leone. Ongoing epidemic in the Democratic Republic of Congo.	Over 30 000 cases; average CFR: 50%83

CFR, case fatality rates.