An article claiming that researchers have not proven that SARS-CoV-2 causes COVID-19 uses outdated criteria and contains incomplete facts to substantiate its arguments. The article focuses on how researchers did not comply with Koch’s postulates – a set of criteria from the 19th century to show that a microbe causes a disease – as it was originally understood.
Koch’s postulates were presented in 1890 (here and here), at a time when germ theory was still controversial and before the discovery of viruses, to which Koch’s postulates, as they were originally written, did not apply. Koch himself acknowledged that the postulates had exceptions (here), and that they have not yet been established for many disease-causing microbes. Modern criteria confirming that a virus causes a disease have been shown for COVID-19.
KOCH SE POSTULATE
The article (here) states: “Koch’s postulates are the decisive criteria for the scientific detection of a virus” then lists these postulates in their original form. Postulate one: “The micro-organism must be detectable in all cases of diseases with the same symptoms, but not in healthy individuals.”
This postulate was obsolete even in Koch’s own time as symptomatic carriers of disease – causing microbes were discovered, prompting Koch to modify or abandon this postulate (here and here and here). Postulate two: “The microorganism can be transferred from the sick individual to a pure culture (isolation).”
It is generally understood that the microbe must be able to grow into something that is a sterile growth medium. Many types of diseases with microbes, including bacteria, can still not be cultured as such (here and here), but are well established as a cause of disease. Viruses cannot reproduce themselves, and therefore cannot be cultured at all as a ‘pure culture’ as Koch would provide, but it is well established that viruses cause diseases (here and here and here). Apostles three and four also cannot be fulfilled as written if the pure culture of the disease is not available.
Postulate three: ‘A previously healthy individual, after infection with the microorganism from the pure culture, shows the same symptoms as the one from which the microorganism originally originated.’
Although deliberate infection of people with diseases has historically been done, it is rare due to ethical issues. However, the UK Ethical Body for Clinical Trials last month approved a COVID-19 challenge study in which healthy young volunteers will be exposed to the SARS-CoV-2 virus in a safe and controlled environment (here).
In most cases, the individuals who use the third postulate tend to be animals. This makes it impossible to fulfill this postulate, and by extension, the fourth postulate, in diseases specific to humans (here). Postulate four: “The microorganism can be transmitted from the infected and sick individuals to a pure culture.” Although it is not an original postulate of Koch (here), it is actually a repetition of step two with another source.
The article further states: “From textbooks (eg White / Fenner. Medical Virology, 1986, p. 9), as well as from leading virus researchers such as Luc Montagnier or Dominic Dwyer, it has been found that the cleaning of particles – ie the separation of ‘ an object of all that is not that object, such as the Nobel Prize winner Marie Curie in 1898 purified 100 mg of radium chloride by extraction from tons of pitchblende – is an essential prerequisite to prove the existence of a virus. The textbook for medical virology can be viewed online (here). Page 9 appears to be missing, but later references to Koch’s postulates (pp. 238-244) acknowledge the limits of these postulates and do not imply that they must be adhered to in order to cause disease. The book notes: ‘two tools that are crucial to help the epidemiologist are immunological examinations and demonstration of the presence of the viral genome in tumor cells using nucleic acid probes or the polymerase chain reaction’. INSULATION The article states that methods of not counting the virus causing COVID-19 as it did not ‘purify the virus’.
Siouxsie Wiles, associate professor at the Department of Molecular Medicine and Pathology at the University of Auckland, addressed claims like this, saying: ‘viruses need a host host to repeat’, so samples of the virus always mix with other genetic material (here and there) here), but it does not prevent the virus from being studied or genetically traced. Luc Montagnier, who is referred to in the article to support his argument that a particle should be isolated to determine causality, specifically rejected the proposition that purification is necessary to isolate viruses (here).
NOTE OF COVID-19 Virus research has been transformed by genetic techniques developed decades after Koch’s death (www.pnas.org/content/106/1/6 and here and here). These techniques were used to identify COVID-19 (here and here and here).
Updated criteria for determining viruses that cause disease are sometimes still called Koch’s postulates (here) This means that animals are infected with the suspected virus (here and here) and that viruses are grown in cells (here), which are not a “pure culture” as Koch would have understood it (here) and would not meet the purification criteria mentioned earlier, although other microbes would be removed (here).
VERDICT False. Koch’s postulates, as originally understood, do not need to be demonstrated to determine that a microbe is causing a disease. SARS-CoV-2 causes COVID-19 and is shown to do so by modern standards, including criteria based on Koch’s postulates, as well as genetic techniques developed only decades after Koch’s death.
This article was produced by the Reuters Fact Check team. Read more about our work to actually check social media posts.