Case definitions determine who may be, and who is, part of an outbreak

31 December 2019 Cluster of cases of pneumonia of unknown aetiology (unknown cause) detected in Wuhan City, Hubei Province, China. China alerted the World Health Organization (WHO) China Country Office. (1)

Case definitions determine who may be, and who is, part of an outbreak. “Pneumonia of unknown aetiology,” is a definition used in surveillance which includes standardised, specific criteria, established following the Severe Acute Respiratory Syndrome (SARS) outbreak in 2002-2003. (2)

Common exposures in those meeting the case definition can then be investigated. The Huanan Seafood Wholesale Market was quickly identified as being associated with the majority of early cases of pneumonia of unknown aetiology. As a result, there was an early intervention to reduce the spread from this source.

1 January 2020 Huanan Seafood Wholesale Market in Wuhan city closed for environmental sanitation and disinfection as it was associated with many early cases of the pneumonia of unknown aetiology outbreak.

Outbreak response requires coordination at all levels. The Central Committee of the Communist Party of China and the State Council launched a national emergency response. Internationally, on 2nd January 2020, the incident management system (IMS) of the WHO was activated. More on the role of the WHO from Dr Socé Fall next week. From 31st December to 3rd January there were 44 people identified with pneumonia of unknown aetiology in Wuhan, China. Identifying the causal agent was essential. Initial investigations found that the outbreak was not due to seasonal influenza, Severe Acute Respiratory Syndrome (SARS) or Middle Eastern Respiratory Syndrome (MERS). Deep sequencing to detect genetic material is the most powerful tool we have to identify organisms, and this was used to identify this novel coronavirus. More on this from Prof Hibberd later in the week.

7 January 2020 The Chinese authorities identified a novel type of coronavirus (subsequently named SARS CoV-2) as a cause of the pneumonia outbreak.

Whole-genome sequence data of the causal agent can be used to develop other, simpler, diagnostic tests. Making these data available quickly was important in developing kits for testing suspected cases.

12 January 2020 China shared the genetic sequence of the novel coronavirus (1)

In this early phase, protocols for diagnosis and treatment, surveillance, epidemiological investigation, management of close contacts and diagnostic testing were being developed.

Other countries were also searching for cases, and then determining whether the case arose from transmission within the country, or if it had been imported. Appropriate public health interventions could then be taken.

13 January 2020 Thailand reported the first confirmed case of the novel coronavirus outside China. This was confirmed as an imported case from Wuhan, China. (1)

Within days, Japan and the Republic of Korea also reported imported cases of a novel coronavirus from Wuhan, China. Cases further afield followed. (1)

Bar chart showing an increase in cases of COVID-19 over the first two months of the outbreak in Wuhan, with interventions taken.

Figure 1. The onset of Illness among the First 425 Confirmed Cases of Novel Coronavirus Infected Pneumonia (NCIP) in Wuhan, China (3)

20 January 2020 The USA reported its first confirmed case, in someone who had returned to Washington State on 15th January 2020 after visiting family in Wuhan, China. (4)

As the outbreak progressed in China, the main strategy was to reduce the intensity of the epidemic and to slow down the increase in cases. China put in place legal measures to support control.

20 January 2020 COVID-19 was included in the statutory report of Class B infectious diseases and border health quarantine infectious diseases in China. (2)

Temperature checks, health care declarations, and quarantine against COVID-19 were instituted at transportation depots in accordance with the law in China. Nationally, wildlife markets were closed and wildlife captive-breeding facilities were cordoned off. The outbreak was also closely monitored internationally.

22 and 23 January The WHO Director-General convened an Emergency Committee under International Health Regulations (2005) on whether to declare the outbreak of novel coronavirus a Public Health Emergency of International Concern (PHEIC). At that time, the advice was that the event did not constitute a PHEIC, but the Committee members agreed on the urgency of the situation and suggested that the Committee should be reconvened in a matter of days to examine the situation further. (5)

Cases in other regions were identified.

24 January 2020 The first report of a case in Europe was reported by Ministère des Solidarités et de la Santé in France. This was not unexpected given the growing number of cases reported outside of China by this time. (6)

Interventions in China continued, with updating of protocols for diagnosis, treatment and epidemic prevention and control; case isolation and treatment were strengthened. On 23rd January strict traffic restrictions were put in place. Other measures included cancelling mass gatherings. More details on the response in China will come in the course next week. The outbreak continued to be closely monitored internationally.

Corona Timeline

30 January 2020 The WHO Director-General declared the 2019 nCoV (former name of COVID-19) outbreak a Public Health Emergency of International Concern under International Health Regulations (2005). (7)

Prof Heymann will discuss the process for declaring a Public Health Emergency of International Concern later in the week. The focus on containing the outbreak continued on the advice of the WHO Scientific and Technical Advisory Group for Infectious Hazards (STAG-IH), working with the WHO secretariat, after reviewing of the information available on 7th February. (8)

11 February 2020 The virus, and the disease it causes, were officially named. The novel coronavirus was named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the disease it causes COVID-19. (9)

Surveillance of the outbreak continued, and with new data, case definitions for COVID-19 were updated.

27 February 2020 WHO updated the case definitions for COVID-19 for suspected, probable or confirmed cases. (10)

Surveillance continued worldwide, and the first case in sub-Saharan Africa was reported.

28 February 2020 Nigeria reports the first case of COVID-19 in sub-Saharan Africa. (1)

The number of cases reported, and the countries with cases have increased, with Iran and Italy particularly affected.

11 March 2020 The WHO Director-General declared the COVID-19 outbreak a pandemic. (11)

Resources for up to date information on the COVID-19 outbreak can be found in the See Also section of this step. The COVID-19 tracker includes updated numbers of cases worldwide.

© London School of Hygiene & Tropical Medicine 2020