Virus scanner: ter info

Viruses do not exist. Viruses are computer simulations that fit observations. They are nothing more than models we create ourselves. No virus has ever been physically isolated, and a definition for 'virus' has been devised that is still not met. Thus the repeated complaints from virus deniers against virus variants. (Those 'postulates' themselves are partly outdated - but that is also another discussion).

All in all a challenging and therefore amusing controversy, but this site is about an infectious respiratory disease - from viruses or something else - and the response to it. The question is how proportionate and substantiated the response was and is, especially in the Netherlands. Call it a virus, an exosome, a replicon, or a self-replicating pathogen - the name does not change the reality: contamination between individuals exists, is experimentally reproducible, and the discussion about what to call it only distracts from pandemic handling: how do we deal with infections: can we prevent or moderate them and at what cost? We still have to learn to deal with infections; viruses or not.

Are there studies on this?

Especially in the initial investigations, forcing infections was not always easy.¹November 2020 article: Hard evidence of infectious aerosols Het druppeldogma zat in de weg. Men heeft het vaak geprobeerd met neusdruppels: vrij kansloos, want dat is alsof je een schuimblusser probeert aan te steken met een lucifer en als dat niet lukt concludeert "er bestaat geen vuur" of "overslaande brand is onmogelijk". De neus, slijmvliezen en bovenste luchtwegen (aka mucosale bescherming) vormen immers de belangrijkste firewall tegen pathogenen, die binnen minuten worden afgevoerd richting slokdarm, weg van de ontvankelijke longen. In latere studies gaat dat een stuk beter. Er staan er hieronder enkele genoemd.

Another basis of evidence is the fact that - in other types of research - serial passage is used: how a pathogen adapts to a new host. This is studied by transferring infections from animals to other animals. So that works without any problems. Also a number of links to studies.

Finally, a few studies with ferrets that infect each other, in different setups. Poor animals...

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Contact or air

1. The Poker Experiment (Dick et al., 1987) ²Dick EC, Jennings LC, Mink KA, Wartgow CD, Inhorn SL. Aerosol transmission of rhinovirus colds. J Infect Dis. 1987;156(3):442-448. PubMed: https://pubmed.ncbi.nlm.nih.gov/3039011/ JSTOR (full text): https://www.jstor.org/stable/30134751

Already treated in 2023³Playing poker with infections https://virusvaria.nl/pokeren-met-besmettingen/:

What happened:

• 8 sick Donors played 12 hours of poker with 12 healthy Recipients
• Half of the Recipients were physically prevented from touching their faces
• A separate experiment tested only contaminated objects (cards, tokens, furniture — zero Donors in the room)

The outcome:

• Aerosol-only: 56% contaminated, all routes: 67% contaminated (difference not statistically significant)
• Fomites-only: 0% besmet

There is something transmissible that goes from person to person through the air. Fomites do nothing. The discussion about what exactly it is, virus or not, is irrelevant to the outcome.

2. EMIT-1 proof-of-concept (2012) ⁴Killingley B, Enstone JE, Greatorex J, et al. Use of a human influenza challenge model to assess person-to-person transmission: proof-of-concept study. J Infect Dis. 2012;205(1):35-43. PubMed: https://pubmed.ncbi.nlm.nih.gov/22131338/ DOI: https://doi.org/10.1093/infdis/jir701

Donors en Recipients in quarantaine without mechanical ventilation.
Secondary attack rate: 16%. Transfer takes place.

3. EMIT-1 follow-on (Killingley et al., 2020) ⁵Nguyen-Van-Tam JS, Killingley B, Enstone J, et al. Minimal transmission in an influenza A (H3N2) human challenge-transmission model within a controlled exposure environment. PLOS Pathog. 2020;16(7):e1008704. Full text (open access): https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1008704 DOI: https://doi.org/10.1371/journal.ppat.1008704

Same setup, but now with mechanical ventilation. Secondary attack rate: 1.3%. Turn on the ventilation, and the transmission disappears. Ventilation only dilutes things floating through the air. The agent appears to be transmissible through the air.
"The main difference between these studies was mechanical building ventilation, suggesting a possible role for aerosols."

4. EMIT-2 — naturally infected Donors, still ventilation dependent⁶Coleman KK, Bischoff W, Tellier R, et al. Evaluating modes of influenza transmission (EMIT-2): Insights from lack of transmission in a controlled transmission trial with naturally infected donors. PLOS Pathog. 2026;22(1):e1013153. https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1013153

Naturally infected Donors (no lab inoculation, mild symptoms, possible cross-immunity in recipients, 8 people 2-4 hours in a room with one donor), limited ventilation but high air recirculation, regulated climate (temp, humidity). Zero transmission. Mild symptoms and cross-immunity probably played a role.
Conclusion: without concentrated respiratory plumes - no transmission.
(Note: they made the donor cough several times. However, they would have been better off letting him sing some carnival songs, as evidenced by this piece in Nature, February 2019⁷Nature, februari 2019 https://www.nature.com/articles/s41598-019-38808-z)

Serial passaging

Serial passage involves infecting a healthy animal with tissue from a sick animal. That healthy animal becomes sick. A healthy animal is then 'infected' with that new lung tissue, etc. → repeat 10-20 times. At the end, the mutations of the tissue are mapped.

5. Serial passaging: A/Kansas/14/2017 H3N2 — 17 passages⁸Dynamic adaptation mutations and pathogenic characterization of a mouse-adapted seasonal human H3N2 influenza virus. Virol J. 2025.
Full text: https://virologyj.biomedcentral.com/articles/10.1186/s12985-025-02793-9

17 passages in mice. Wild type: zero detectable RNA in lungs. Passage 17: $10^{10}$1010 copies/mL, lethal. Fourteen specific mutations accumulated (Virology Journal, 2025).

6. Serial passaging: A/Switzerland/9715293/2013 H3N2⁹Synergistic PA and HA mutations confer mouse adaptation of a contemporary A/H3N2 influenza virus. Sci Rep. 2019;9:16616. Full text: https://www.nature.com/articles/s41598-019-51877-4 DOI: https://doi.org/10.1038/s41598-019-51877-4

Serial passages, polymerase activity increased >300%. Synergistic mutations in HA and PA caused lethal pneumonitis where the wild type did nothing (Scientific Reports, 2019).

7. Serial passaging: A/HK/1/68 H3N2 — genomische analyse¹⁰Ping J, Keleta L, Forbes NE, et al. Genomic and protein structural maps of adaptive evolution of human influenza A virus to increased virulence in the mouse. PLOS One. 2011;6(6):e21740. Full text: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021740

39 variants from 10 independent passages. 51 of 115 mutations under positive selection, 27 parallel mutations. Virulence increased by factor >$10^5$105.

8. Serial passage: SARS-CoV-2 Beta — IFITM3 as a barrier¹¹IFITM3 deficiency drives SARS-CoV-2 adaptation while preserving variant-specific traits. Nat Commun. 2026. Full text: https://www.nature.com/articles/s41467-026-68485-2

20 passages in IFITM3-deficient mice. Virus replicated more efficiently in mice, but at the same time lost fitness in human cells. A classic host-adaptation trade-off (Nature Communications, 2026).

9. Serial passing: SARS-CoV-2 Beta and Delta — parallel evolution¹²SARS-CoV-2 rapidly evolves lineage-specific phenotypic changes during serial passage in hACE2 transgenic mice. Commun Biol. 2024;7:248. Full text: https://www.nature.com/articles/s42003-024-05878-3

20 passages. Early passage virus (P2) versus late (P21): dramatic difference in virulence, weight loss, and mortality. TNF-deficient mice were spared — the mechanism has been causally demonstrated (PNAS, 2023).

10. Serial passaging: SARS-CoV-2 N501Y VIC2089 — 21 passages¹³SARS-CoV-2 mouse adaptation selects virulence mutations that cause TNF-driven age-dependent severe disease with human correlates. PNAS. 2023. PubMed: https://pubmed.ncbi.nlm.nih.gov/37523564/

21 passages. Early passage virus (P2) versus late (P21): dramatic difference in virulence, weight loss, and mortality. TNF-deficient mice were spared — the mechanism has been causally demonstrated (PNAS, 2023)

11. Natural serial passage on an industrial scale: Danish mink¹⁴Emergence and spread of SARS-CoV-2 variants from farmed mink to humans and back during the epidemic in Denmark, June-November 2020. PLOS Pathog. 2024;20(7):e1012039. Full text: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1012039

Large-scale natural serial passage. ~136 human-to-mink transmissions, ~59 mink-to-human transmissions, mink-to-mink transmission between farms. The Y453F Spike mutation emerged early and dominated — population-scale adaptive evolution (PLOS Pathogens, 2024).

12. H5N1 — transmission between mammals¹⁵Eisfeld AJ, Biswas A, Guan L, et al. Pathogenicity and transmissibility of bovine H5N1 influenza virus. Nature. 2024. https://www.nature.com/articles/s41586-024-07766-6

Bovine H5N1 transmission from mother to pup in mice. Inefficient but real respiratory droplet transmission in ferrets. The authors: "a paradigm shift."

13. Bonus: systematic review confirms aerosol as dominant route¹⁶Transmission route of rhinovirus — the causative agent for common cold. A systematic review. Am J Infect Control. 2023;51(4):438-445. https://www.ajicjournal.org/article/S0196-6553(22)00866-5/fulltext

Conclusion after 25 studies: "Moderate evidence that airborne transmission is the major transmission route of rhinovirus in real-life indoor settings."

Physically separated ferrets

These are perhaps the strongest experiments yet.

14. Zhou et al. (2018) — from impactor-studie¹⁷Zhou J, Wei J, Choy KT, et al. Defining the sizes of airborne particles that mediate influenza transmission in ferrets. PNAS. 2018;115(10):E2386-E2392. PubMed: https://pubmed.ncbi.nlm.nih.gov/29463703/ Full text: https://www.pnas.org/doi/10.1073/pnas.1716771115

The setup:

• Two stainless steel chambers, one for Donor frets, one for Recipient frets
• Connected by a impactor — a plate with holes that separates particles by size
• Four different impactors tested: 50% capture efficiency at 9.9μm, 5.3μm, 2.5μm, en 1.0μm
• Air flow exclusively from donor to recipient chamber via a vacuum pump
• HEPA filters on inlet and outlet

Large droplets (>10μm) are struck against the impaction plate due to their mass and inertia. Only small aerosols make the turn and reach the receiver.

Results:

• Transmission via particles >1.5μm was successful
• With the 9.9μm and 5.3μm impactors: transmission occurred
• With the 2.5μm impactor: reduced transmission
• With the 1.0μm impactor: no transmission via natural exhalation - but there is with artificial aerosolization of the virus
• Donors were the most contagious for fever, and remained contagious for up to 5 days
• Viral load in the air correlated with transmission success

The implication: the infectious particles are in the fine aerosol fraction (1.5-10μm), not in the large droplets that settle within a meter. This explains why ventilation has such a dramatic effect in the EMIT studies — it dilutes precisely these particle sizes.

15. Kutter et al. (2012) — pandemic vs seasonal influenza in ferrets¹⁸Kutter JS, Spronken MI, Fraaij PL, Fouchier RA, Herfst S. Exhaled aerosol transmission of pandemic and seasonal H1N1 influenza viruses in the ferret. PLOS One. 2012;7(4):e33118. Full text: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0033118

The setup:

• Two rooms connected by one 7×7×15cm tunnel with mesh at both ends
• Air flow 12 L/min from donor to recipient
• No direct contact possible — only what floats through the tunnel
• Exposure: 3 hours (to approximate real human exposure time) and continuous (>24 hours)

Results:

• Continuous exposure: robust transmission
• 3-hour exposure: viral RNA in the throat, but below the infection threshold
• Seasonal flu produced lake virus in exhaled air, but pandemic strains were more efficient in transmission, i.e. more transmission per exhaled virus particle
• This shows that transmission efficiency depends not only on the amount of exhaled virus, but also on intrinsic properties of the strain

16. Turgeon et al. (2019) — the three-chamber setup with particle separator¹⁹Turgeon N, Hamelin MÈ, Verreault D, et al. Design and validation with influenza A virus of an aerosol transmission chamber for ferrets. Int J Environ Res Public Health. 2019;16(4):609. Full text: https://www.mdpi.com/1660-4601/16/4/609

The setup:

• Three airtight chambers in series — index ferret in cage 1, two naive ferrets in cages 2 and 3
• Air flows from cage 1 → cage 2 → cage 3
• Between cage 2 and 3: a particle separator with adjustable cut-off size (5-8μm aerodynamic diameter)
• Cage 2 receives drops + aerosols; cage 3 receives only aerosols
• Ferrets stayed in the setup for 10-12 days — long-term natural exposure

Results:

• Influenza transmission via aerosols-only (cage 3): 2 out of 3 experiments
• Influenza transmission via aerosols + droplets (cage 2): 3 out of 3 experiments

The inescapable conclusion

The first few studies mentioned speak for themselves.

With serial passage, if it were a static toxin, each passage would greatly dilute it. You should see no more disease after 3-4 passes. It must therefore multiply in a host to regain a pathogenic effect ('viral' aspect).

You even see the reverse of weakening: the contagiousness of the disease becomes stronger, the agent adapts, the same mutations appear in independent experiments, and it develops resistance to antibodies.

The ferret experiments prove robust contamination (via aerosols).

Either way: something is replicating. Something mutates. Something evolves. A disease is transmissible from individual to individual. So again:

"Noem het een virus, een exosoom, een replicon, of een zichzelf vermenigvuldigend pathogeen agens - de naam verandert niets aan de realiteit: besmetting van een ziek naar een (vatbaar) gezond individu bestaat, is experimenteel reproduceerbaar, en de discussie over hoe we het moeten noemen leidt alleen maar af van de pandemie-handling: hoe kunnen we besmettingen voorkomen, matigen en behandelen."

Again: it's the aerosols

The public health implications are far-reaching, especially as current recommended measures to limit the spread of COVID-19 focus on social distancing, wearing face masks when around others and washing hands. As for aerosol transmission, measures such as physical distancing of one and a half meters indoors does not helpone false sense of security give and lead to exposure and outbreaks. Given the current rise in cases, clear guidance on control measures against SARS-CoV-2 aerosols is essential to help contain the COVID-19 pandemic…

The public health implications are broad, especially as current best practices for limiting the spread of COVID-19 center on social distancing, wearing of face-coverings while in proximity to others and hand-washing. For aerosol-based transmission, measures such asphysical distancingby 6 feet wouldnot be helpful in an indoorsetting,provide a false-sense of securityand lead toexposuresandoutbreaks. With the current surges of cases, to help stem the COVID-19 pandemic, clear guidance on control measures against SARS-CoV-2 aerosols are needed
International Journal of Infectious Diseases, November 2020²⁰IJID,November 2020:-Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients

The cover-up committee sits there and stares impassively when the one and a half meter rule is discussed. The drip dogma has brought an incredible amount of misery.

The dogma that infections of respiratory diseases occur via droplets and/or fomites creates more room for research in which an error - such as a lab accident - can have epidemic consequences. Thanks to the drip dogma, this danger is not recognized and experiments become easier and cheaper to carry out.

The basic assumption for any infectious respiratory disease should be that transmission occurs through the air unless proven otherwise. However uncomfortable that may be for virologists and pharmaceutical companies.

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Footnotes

• 1
  November 2020 article: Hard evidence of infectious aerosols
• 2
  Dick EC, Jennings LC, Mink KA, Wartgow CD, Inhorn SL. Aerosol transmission of rhinovirus colds. J Infect Dis. 1987;156(3):442-448. PubMed: https://pubmed.ncbi.nlm.nih.gov/3039011/ JSTOR (full text): https://www.jstor.org/stable/30134751
• 3
  Playing poker with infections https://virusvaria.nl/pokeren-met-besmettingen/
• 4
  Killingley B, Enstone JE, Greatorex J, et al. Use of a human influenza challenge model to assess person-to-person transmission: proof-of-concept study. J Infect Dis. 2012;205(1):35-43. PubMed: https://pubmed.ncbi.nlm.nih.gov/22131338/ DOI: https://doi.org/10.1093/infdis/jir701
• 5
  Nguyen-Van-Tam JS, Killingley B, Enstone J, et al. Minimal transmission in an influenza A (H3N2) human challenge-transmission model within a controlled exposure environment. PLOS Pathog. 2020;16(7):e1008704. Full text (open access): https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1008704 DOI: https://doi.org/10.1371/journal.ppat.1008704
• 6
  Coleman KK, Bischoff W, Tellier R, et al. Evaluating modes of influenza transmission (EMIT-2): Insights from lack of transmission in a controlled transmission trial with naturally infected donors. PLOS Pathog. 2026;22(1):e1013153. https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1013153
• 7
  Nature, februari 2019 https://www.nature.com/articles/s41598-019-38808-z
• 8
  Dynamic adaptation mutations and pathogenic characterization of a mouse-adapted seasonal human H3N2 influenza virus. Virol J. 2025.
  Full text: https://virologyj.biomedcentral.com/articles/10.1186/s12985-025-02793-9
• 9
  Synergistic PA and HA mutations confer mouse adaptation of a contemporary A/H3N2 influenza virus. Sci Rep. 2019;9:16616. Full text: https://www.nature.com/articles/s41598-019-51877-4 DOI: https://doi.org/10.1038/s41598-019-51877-4
• 10
  Ping J, Keleta L, Forbes NE, et al. Genomic and protein structural maps of adaptive evolution of human influenza A virus to increased virulence in the mouse. PLOS One. 2011;6(6):e21740. Full text: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021740
• 11
  IFITM3 deficiency drives SARS-CoV-2 adaptation while preserving variant-specific traits. Nat Commun. 2026. Full text: https://www.nature.com/articles/s41467-026-68485-2
• 12
  SARS-CoV-2 rapidly evolves lineage-specific phenotypic changes during serial passage in hACE2 transgenic mice. Commun Biol. 2024;7:248. Full text: https://www.nature.com/articles/s42003-024-05878-3
• 13
  SARS-CoV-2 mouse adaptation selects virulence mutations that cause TNF-driven age-dependent severe disease with human correlates. PNAS. 2023. PubMed: https://pubmed.ncbi.nlm.nih.gov/37523564/
• 14
  Emergence and spread of SARS-CoV-2 variants from farmed mink to humans and back during the epidemic in Denmark, June-November 2020. PLOS Pathog. 2024;20(7):e1012039. Full text: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1012039
• 15
  Eisfeld AJ, Biswas A, Guan L, et al. Pathogenicity and transmissibility of bovine H5N1 influenza virus. Nature. 2024. https://www.nature.com/articles/s41586-024-07766-6
• 16
  Transmission route of rhinovirus — the causative agent for common cold. A systematic review. Am J Infect Control. 2023;51(4):438-445. https://www.ajicjournal.org/article/S0196-6553(22)00866-5/fulltext
• 17
  Zhou J, Wei J, Choy KT, et al. Defining the sizes of airborne particles that mediate influenza transmission in ferrets. PNAS. 2018;115(10):E2386-E2392. PubMed: https://pubmed.ncbi.nlm.nih.gov/29463703/ Full text: https://www.pnas.org/doi/10.1073/pnas.1716771115
• 18
  Kutter JS, Spronken MI, Fraaij PL, Fouchier RA, Herfst S. Exhaled aerosol transmission of pandemic and seasonal H1N1 influenza viruses in the ferret. PLOS One. 2012;7(4):e33118. Full text: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0033118
• 19
  Turgeon N, Hamelin MÈ, Verreault D, et al. Design and validation with influenza A virus of an aerosol transmission chamber for ferrets. Int J Environ Res Public Health. 2019;16(4):609. Full text: https://www.mdpi.com/1660-4601/16/4/609
• 20
  IJID,November 2020:-Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients