Report of the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19) | INTENSIVE Review

Report of the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19). 16-24 February 2020. [Accessed 7 April 2020] Available at URL: https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf

Report of the WHO-China Joint mission on COVID-19 is a key document prepared by 25 national and international experts from China, Germany, Japan, Korea, Nigeria, Russia, Singapore, the United States of America and the World Health Organisation. This document provides a detailed description of the epidemic in China along with the measures taken by the Chinese government to control the epidemic. It also identifies major knowledge gaps in the natural history of the disease and the prevention of disease spread. This document was published on 24^th February. The data from this report have helped in modelling the disease outbreak in the rest of the world.

This post provides a summary of the report for clinicians managing COVID-19.

The SARS-CoV-2 virus

• Zoonotic virus
• Caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (previously called novel coronavirus)
• Isolated from BAL samples taken on 30^th Dec 2019, from a patient with pneumonia of unknown cause in Wuhan Jinyintan Hospital.
• Belongs to Betacoronavirus 2B lineage
• Forms a clade within the subgenus sarbecovirus, Orthocoronavirinae subfamily
• 96% identical to bat SARS-like coronavirus strain BatCov RaTG13
• 104 strains isolated from various parts of China during the outbreak which showed 99.9% homology without any significant mutation.
• Causes bilateral diffuse alveolar damage with fibromyxoid exudate with changes consistent with acute respiratory distress syndrome
• Virus isolation from various inoculated cell lines (for eg human airway epithelial cells), demonstration of cytopathic effects, inoculation of transgenic animal models with the virus and subsequent detection and isolation from the lung and intestinal tissue of infected animal demonstrated that SARS-CoV-2 caused COVID-19.

The Outbreak (see Figure 1)

• Bat is the reservoir -> Unknown intermediate host -> animal to human transmission
• Most likely occurred in Hunan Wholesale Seafood Market, Wuhan, Hubei Province
• Visitors and workers to the market acquired infection initially
• Human to human spread occurred at some point afterwards which seeded the community outbreak in Wuhan and then to Hubei province
• During the Chinese New Year period infected individuals quickly spread the disease throughout China and the rest of the world
• Majority of limited local transmission outside Wuhan in China occurred in household contacts.
• Estimated basic reproduction number Ro (average number of secondary cases from one case in a susceptible population) — 2-2.5
• 3 Jan 2020- WHO notification about the epidemic by China
• 10 Jan 2020- whole genome sequencing shared by China
• 23 Jan 2020- cordon sanitaire around Wuhan and neighbouring municipalities
• By 20 Feb 2020- total 55,294 laboratory confirmed cases in China
• Samples collected between November and December 2019, from severe acute respiratory infection and influenza-like illness surveillance systems did not test positive for SARS-CoV-2 suggesting that there was no disease in the community prior to its detection

Figure 1. Schematic showing the spread of outbreak from Wuhan to the rest of China.

Routes of Transmission

• Droplet and fomite transmission
  • Primary mode
  • Close, unprotected contact between the infector and infectee
• Airborne spread-
  • not reported,
  • possible in health care facilities with aerosol-generating procedures
  • not a major driver of transmission
  • Recent simulation studies show that in an aerosolized environment the virus is alive up to 3 hours.
• Faecal-oral route
  • role and significance yet to be determined
• Transmission in health care settings and among health care workers
  • 2,055 HCWs- 88% from Hubei- had COVID-19 diagnosis
  • High during the initial part of the outbreak in Wuhan when experience with the disease was lower
  • Few from nosocomial outbreaks in Wuhan
  • Probably most contracted from household cases

Age

• median age 51 (IQR 39-63) yrs
• Age range 2 days – 100 yrs
• 77.8% of patients between 30-69 yrs
• COVID-19 in Children (<19 yrs age)
  • 2.4% of all reported cases from China
  • Role in disease transmission yet to be established
  • Children identified mainly through contact tracing
  • Child to adult transmission not described in China
  • 2.5% of children develop severe disease
  • 0.2% of children develop critical disease

Sex

• Males – 51.1% of cases

Signs, Symptoms, disease progression and severity (see Table 1 and Figure 2)

• These are based on 55,294 lab-confirmed cases of COVID-19 in China
• Mean Incubation period 5-6 days (range 1-14 days)
• Median time from onset to clinical recovery
• For mild disease approximately 2 weeks
• For severe of critical disease- 3-6 weeks
• Fever, dry cough, fatigue and sputum production are the most common symptoms. (See Table 1 for other symptoms)
• Atypical symptoms of diarrhoea, nausea and vomiting are also seen.
• Disease severity ranges from asymptomatic infection to severe pneumonia and death
• Asymptomatic infection
  • Proportion of truly asymptomatic infection- unknown, most likely rare
  • Most go on the develop symptoms after the test is positive
• Mild to moderate disease
  • Seen in approximately 80%
  • Includes non-pneumonia and pneumonia cases
• Severe disease
  • Definition- RR≥30 breaths/min, or SpO₂ ≤93% at rest, or PaO₂/FiO₂ <300 mmHg and/pr lung infiltrates >50% of lung field within 24-48 hours
  • Seen 13.8% of cases
  • Time from symptom onset to severe disease- approximately 1 week
• Critical disease
  • Seen in 6.1% of cases
  • Definition-Respiratory failure, Septic Shock, MODS/MOF
• High-risk groups for severe infection and death
  • >60 yrs age
  • Comorbid conditions- HT, DM, cardiovascular disease, chronic respiratory disease and cancer

Table 1. Typical signs and symptoms of COVID-19

Mortality

• Most patients with mild/moderate disease recover
• Crude Fatality Ratio 3.8%
• Time from disease onset to death – 2-8 weeks
• CFR varies by location, the intensity of transmission and over time based on interventions to control the disease
• Highest mortality >80 yrs (21.9%)
• Higher amongst males (4.7% vs 2.8%)
• Higher rates in patients with co-morbid conditions: cardiovascular disease (13.2%), DM (9.2%), HT (8.4%), chronic respiratory disease (8.0%), and cancer (7.6%)

Figure 2. COVID-19 disease spectrum and outcome. Most of the patients recover from the illness.

The Chinese response to the epidemic

Chinese government’s aggressive use of non-pharmaceutical interventions- case isolation, scrupulous contact tracing, quarantining of contacts,  social distancing,  school closures, and lock-down measures –  contained and reversed the epidemic all over China including the worst affected areas in Wuhan. China isolated all the cases, built several hospitals, co-ordinated provision of medical supplies and transferred health care workers to the worst affected areas to treat the patients aggressively. The report gives detailed accounts of all the steps taken by the government to achieve this. Thus, the report provides a roadmap to contain the pandemic in other parts of the world.

Also, the report provides a list of recommendations for the rest of the world which had not seen many cases of COVID-19 when the report was published. The main recommendations for all the regions included aggressive case detection by testing and case isolation, meticulous contact tracing and quarantining the contacts.

Concluding remarks

In summary, for every epidemiologist and clinician managing COVID-19 patients, this is a key document. It provides a description of the basic epidemiology of COVID-19, enumerates the strategies that have worked in controlling the epidemic in China, and identifies knowledge gaps that need to be filled with future research.

Further reading

1. World Health Organisation. Report of the WHO-China joint mission on coronavirus disease 2019 (COVID-19). [Accessed 7 April 2020]. Available from URL: https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf
2. Zhu N, Zhang D, Wang W, et al. A Novel Coronavirus from Patients with Pneumonia in China, 2019. New England Journal of Medicine 2020;382(8):727-733. DOI: 10.1056/NEJMoa2001017
3. van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. New England Journal of Medicine 2020. DOI: 10.1056/NEJMc2004973