COVID-19

I am moving my English blogs on COVID-19 and ORTEC to this site.
Nederlands

Simple and complex

Basis of virology is simple.
More infections imply

  • More people with disease
  • More hospitalizations
  • More lockdown
  • More economic damage
  • More damage to society
  • More people with long-covid
  • More deaths
  • Virus epidemics grow exponential.
    • Weekly doubling imply 1000-fold after 10 weeks.
    • More infections are harder to control
  • More virus variants will evolve
Herd immunity might end an epidemic when the maximum number of people has been infected or vaccinated if the virus induces lasting sterilizing immunity.
  • Coronaviruses don’t induce herd immunity.
  • Herd immunity through natural infection has never been a strategy against a severe pathogen.

Some aspects of SARS-2 are more complex, but these do not change the list above:

Excess mortality correlates with corona-related mortality
Virus-immune pathology
  • Acute mortality due to wrong immune activation
  • Escapes of early neutralization by immune system
  • Late onset on immune activation
  • Immune overreaction on high virus load
  • Immune suppression mitigates severe disease

Who will develop long covid?

Long covid has been seen frequently in all age groups and all severities, in about 1 in 10 patients
  • In contrast to acute disease, little is known about long covid.
  • Long covid is probably a collection of diseases and mechanisms.
  • The risk of long covid does not have a strong association with age or disease severity.
  • About 5 to 15% still have serious complaints after 3 months. The number of diseased people declines over time but still about 1% might suffer more than a year.
  • We do not know if it will cure spontaneously in all cases. ​
Acute disease is severe
  • Pneumonia
  • Delayed acute sepsis-like disease
  • Risk factors identified
    • Elderly
    • Male
    • Cardiovascular disease
    • Diabetes
    • Overweight
    • Diminished cellular immune responses
    • Decrease type I interferon production
    • Vitamin D deficiency
  • Relative high risk of death for every group
    • Serious for children compared to other childhood diseases
Long-term disease is serious
  • Neurological damage (brain fog, loss of smell/taste)
  • Immune dysregulation
  • Damage to various organs
  • Different risk factors (women, most unidentified)
    • Little difference between young-old
    • Possible related to immune escape virus & mild disease
Symptoms are poor indicator of infectivity
  • Most virus before symptoms
  • Asymptomatic people can spread the virus
  • RT-PCR is most sensitive test
  • Rapid antigen test is good indication of infectivity at that timepoint.
Immunity wanes
  • After infection and vaccination.
  • Rapid loss of sterilizing immunity
    • No chance on herd immunity
  • Reinfections can cause (severe) disease
  • Virus never fades out - unlike influenza
  • Vaccines protects against disease for 6-9 months
Seasonal variation in R0
  • In moderate climate higher R0 in winter
Facemasks protect from infection
  • Medical facemasks offer better protection
Virus variants might cause more severe disease
  • Higher virus titers
  • Later innate immune control by better escape
  • Antigen-specific escape
This has impact on strategies how to control the epidemic.