Table 1

Epidemiological and other characteristics of events

Event	PHEIC Declaration3 4	Date of initial event detection	WHO notified of event	Date of first EC3 4	No countries affected prior to first EC	No countries affected at declaration or, if not declared, no countries affected by last EC	No countries affected over course of event	Regions affected over course of event	Case fatality ratio
H1N1 (2009)	Declared PHEIC	18 March 2009: initial cases of influenza-like illness detected27	24 April 2009: WHO releases first disease outbreak News on H1N1 and influenza-like illness in USA and Mexico27	25 April 2009	23	23	>21427 *	Worldwide27	Of symptomatic cases: 0.0275% (range: 0% –1.2%)28
MERS-CoV (2013)	PHEIC not declared	13 June 2012: first novel coronavirus case admitted to hospital29	22 September 2012 WHO first notified of novel coronavirus11	9 July 2013	911	2611 12	2711 30	Middle East, Africa, Southeast Asia, Europe, North America11	36% (range: 20%–43%)31–34
Polio (2014)	Declared PHEIC	1 January 2014: trend of rising poliovirus international spread noted3	1 January 2014: trend of rising poliovirus international spread noted3	28–29 April 2014	103	103	1735 36	Africa, Middle East, Pacific35 36	Estimated 0.025%–0.05%37
EVD (2014)	Declared PHEIC	26 December 2013: first case develops symptoms38	23 March 2014: Guinea MoH notifies WHO of EVD outbreak with 49 cases and 29 deaths14	6–7 August 2014	414	414	10²⁶	Africa, North America, Europe39	62.9%40
Zika (2016)	Declared PHEIC	1 July–28 November 2015: detection of relationship between Zika and neurological disorders15	1 December 2015: WHO & PAHO publish joint findings on Zika and neurological disorder relationship15	1 February 2016	2516 17	2516 17	8717 41	Africa, North America, South America, Central America, Southeast Asia, Western Pacific17 41	For fetuses born to Zika-infected mothers: 8.3% –10.5%42 43
Yellow Fever (2016)	PHEIC not declared	5 December 2015: first cases identified18	21 January 2016: Angola notifies WHO of Yellow Fever outbreak18	19 May 2016	43	43	444	Southeast Asia, Africa3 44	8.8%45
EVD (2018)	PHEIC not declared	3 May 2018: Provincial Health Division reports febrile, haemorrhagic cases and deaths19	8 May 2018: DRC MoH notifies WHO19	18 May 2018	146	146	146	Africa46	61%47
EVD (2018)	Declared PHEIC	28 July 2018: North Kivu Provincial Health Division notified DRC MoH of acute haemorrhagic fever cases3	1 August 2018: EVD cases confirmed, DRC MoH declares outbreak3	17 October 2018	13	23	23	Africa3	67%14
COVID-19 (2020)	Declared PHEIC	24 December 2019: Wuhan city health commission notes cases of viral pneumonia48	31 December 2019: WHO China Country Office notified of cases of pneumonia of unknown aetiology⁴¹	22–23 January 2020	43	183	21349 *	All regions affected21	Too early to report

Polio spread over course of event is non-cumulative. Information is current as of 9 March 2020.
*Includes countries, territories and areas.
EC, Emergency Committee; EVD, Ebola virus disease; H1N1, influenza A; MERS-CoV, Middle East respiratory syndrome coronavirus; MoH, Ministry of Health; PAHO, Pan American Health Organization; PHEIC, Public Health Emergency of International Concern.