Two hundred experiments set out to give healthy people a cold on purpose. The commonest result was that nobody caught anything.
The person who assembled that record is Daniel Roytas, a naturopath who lectured in naturopathic and nutritional medicine. He had spent a decade teaching infectious disease management, so when he first heard the claim that germs do not cause illness, he expected to dismiss it quickly. Instead he went to the primary literature in 2020 and stayed there for eighteen months, working through more than a thousand cited papers. That record lets you check this:
- The 203 catalogued human experiments, and what they kept finding
- A four-step test science wrote for itself, and how to apply it to any claim
- Grouped illness, which can point to shared surroundings rather than transmission
- Expectation alone, which has produced and dissolved a documented cold
- A steadier way to sit with a health question that unsettles you
What he found was not a single dramatic study. It was a pattern across the whole published record, and that pattern is what makes it worth your attention. Holding a question like this without rushing to a side is a skill, and the free course on observing your reactions before judging them builds it quietly.
Grouped illness is real, and it does not name its own cause
Someone visits a sick friend. Three days later they are ill. The sequence feels like proof, and it is worth being precise about what it actually shows.
It shows that two people shared something. It does not identify what that something was.
Medicine has fallen into that gap before, more than once. Sailors went down with scurvy in sequence for three centuries while doctors called it catching. Pellagra emptied wards and closed schools in the American South before anyone suspected diet. Both were missing nutrients.
The starkest case came in 1956. A fishing village in Japan watched neighbours, and then the local cats, lose control of their limbs and speech. Houses were scrubbed and the sick shut away. The poison was in the bay, dumped there by a factory.
Every one of those outbreaks clustered exactly as an infection would. The clustering was never the error. Reading a cause into it was.
An explanation medicine held for centuries, then set aside
The explanation you grew up with is newer than the one it pushed aside. For most of medical history the blame fell on air, damp and the turn of the seasons. Doctors made a speciality of it, charting pressure and humidity against the day an outbreak began.
By the early 1800s something like nine in ten British physicians did not think influenza was catching. That was not stubbornness. They had watched nurses tend flu patients through an entire epidemic and stay perfectly well. They had also seen one outbreak reach two far-apart cities on a single day, then take weeks to cover sixty kilometres.
A quarrel ran underneath all of it. Antoine Béchamp, working alongside Louis Pasteur, held that tiny particles within us change form to suit the tissue around them. Microbes would then be gathering at damage they had not caused. Surgeons reached much the same view from the operating table. One found his patients fared better washed with clean water than dosed with carbolic acid.
Apply the test science wrote for itself
You do not need a laboratory to check a germ claim. Medicine published its own checklist in the 1880s, and it runs to four conditions. Find the microbe in the sick and not the well. Grow it clean, on its own. Give it to a healthy host and watch the same illness appear. Then pull it back out of that host.
Anyone can hold a claim against those four conditions. What makes the history uncomfortable is that their author kept failing them. His cholera bacterium turned up thriving in people who felt perfectly fine, and condition one falls at that hurdle.
Viruses got their own version of the rules in 1937. Buried in the same paper, the man writing them admitted no one had ever actually seen a virus, and flagged places where his own criteria collided.
Today's version happens in a dish. A sick person's filtered fluid joins animal cells, antibiotics and serum, and when those cells start dying the dying is counted as the virus at work. The difficulty is that untouched dishes die too. The team behind the Nobel-winning measles work of 1954 wrote exactly that into their paper, and it changed nothing about how the method was used afterwards.
What the transmission record actually shows
Count them up and 203 attempts stretch from 1906 to 2020. About one exposed volunteer in three fell ill. So did about one in ten of the people handed nothing but salt water. Seventy-three of the studies failed to sicken a single participant.
The largest effort of all came in 1918, mid-pandemic. Military and public health teams ran 25 trials across three quarantine islands, working through 161 fit young men. They swabbed sick men's secretions into their noses, put sick men's blood under their skin, and sat them at the bedside to be breathed and coughed on at close range. Two caught flu.
If you keep one figure from all of this, make it a 1920 trial. Salt water alone brought on colds in nearly one recipient in five. The same researcher, dripping real mucus from flu sufferers into other noses, managed a lower rate than that.
When the dummy beats the real thing, any result without a control arm becomes hard to read. That is the same patient weighing I bring to a decision someone has been circling for months, because the habit travels well past health.
Expectation can produce a cold, and dissolve one
Picture a volunteer in 1930. He is informed that the fluid going up his nose came from someone with a streaming cold. It was sterile broth. By that evening he was properly unwell. Told the truth over breakfast, he was fine inside an hour.
File that under mechanism, not oddity. Researchers tracking over 2,500 people found the ones who expected to stay well largely did, and it held whichever arm of the trial they landed in. Elsewhere, cancer patients receiving only salt water lost their hair and felt sick, having been led to believe the drug was going in.
The same process runs between people. States pass through groups with no physical agent involved, which is why yawning spreads round a room. Its strongest form has real symptoms moving through a crowd with no toxin ever found. In 1990 more than four thousand people across eight towns sought care after an unusual smell was noticed. Teachers and doctors initially called it influenza. Patients recovered within fifteen minutes to two hours, and an international investigation found no cause.
Openness is doing quiet work in results like these. The people I see improve are usually the ones still willing to entertain a possibility they had already written off. I set that pattern out in these accounts of what openness made possible, and it has held ever since.
Weather, air and season shape the same symptoms
Here is the part that tends to land hardest, because it can be measured. Track the water actually held in the air, whatever the temperature reads, and flu follows it. Drop below a certain point and the risk climbs steeply. Some agencies forecast outbreaks from that number alone, without reference to anyone being infectious.
Cold on its own does plenty too. Two wartime trials put soldiers in wet trenches for three days and they sickened at four times the rate of the men in dry barracks. In a smaller test, ninety people sat with their feet in iced water and came down with colds at nearly triple the rate of those who did not.
Then there is what you breathe. Fine particles turn the thin fluid lining your airways more acidic. Cross a threshold and those lining cells start dying off and shedding, and the cough, the mucus and the inflammation that follow are precisely what gets called a cold. Winter stacks the deck, trapping dirty air low and adding what home heating puts into it.
Hold the question, rather than swapping one certainty for another
Nobody is asking you to decide germs are imaginary. The book is careful on this, disclaiming any medical guidance and any such assertion, and that framing shapes how it should be read.
The takeaway is a habit rather than a belief. Begin a disputed question near zero conviction instead of full. Build upward as evidence arrives. Keep the position loose, and watch for the moment certainty outruns what you can actually show.
That steadiness reaches well past colds and flu. It applies to every claim about your body you will meet in a lifetime, and it is the difference between reacting to a headline and reasoning through one.
None of this is medical advice, and none of it replaces your own doctor. Take it alongside the care you already have rather than instead of it, and raise anything that interests you with the clinician who knows your situation.
If a health question or a stuck situation would be easier to face with calm company, you can think it through together at an unhurried pace. Or begin on your own and put the question straight to the source and reason through the answer whenever it suits you.