CROI 2020 – COVID-19 transmission rate may be lower than expected

  • Liz Scherer
  • Conference Reports
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  • COVID-19 transmission rates might be lower than expected, according to Zunyou Wu, MD, PhD, chief epidemiologist of the Chinese Centers for Disease Control and Prevention.

Why this matters

  • While initial Chinese household transmission rates were 10% early in the outbreak, they quickly fell to 3%; highlighting the value of early diagnosis and isolation.
  • The likelihood of transmission was greatest at symptom onset but declined shortly thereafter.
  • Advise HIV-infected persons to have >30 days of HIV medication supply, set up an advanced care plan (including telemedicine), ensure influenza and pneumonia vaccinations are current.

Key points

  • Transmission from presymptomatic persons appears to be rare.
  • Viral shedding persists for 7-12 days in mild/moderate cases, >2 weeks in severe cases.
  • Initial population quarantine lasting 10 days across the entire Chinese population interrupted the transmission cycle for several weeks, leading to a steep decline in new cases and mortality rates.
  •  ~60M people in Hubei were placed in ‘cordon sanitaire’ (restricted movement in/out of a geographical area) for 50 days.
  • Data are currently lacking for immunocompromised people but severe illness risk is high for HIV-infected persons with lower CD4 cell counts and unsuppressed viral loads.
  • Incubation period averages 4-6 days.
  • Recovery: mild cases=2 weeks, more severe cases=3-6 weeks; mortality observed 2 months of symptom onset.
  • Common symptoms in hospitalized Chinese patients: fever, dry cough, headache, fatigue.
  • Truly asymptomatic cases are uncommon; most patients will develop symptoms.
  • Paediatric data are limited, possibly due to underreporting.
  • People with comorbid hypertension, diabetes, cardiovascular disease, chronic respiratory illness are at increased risk.
  • Case fatality rates: 0.5% to 3.5%; rates in >60 years=5% approaching 16% in ages >80; mortality linked to acute respiratory distress syndrome.


Reports of gastrointestinal manifestations are, "probably red herrings." Dr Wu emphasized while the virus has been isolated in stool, there is no evidence of fecal-oral transmission.