How We Know
This slate says solved. That claim rests on proving a negative, which is harder than proving a positive and is the reason certification took two years after the last case. This page covers how smallpox was counted, why the counting was wrong by two orders of magnitude for most of the programme, and what is not measured now.
Why This Disease Was Measurable At All
Three properties made smallpox findable, and none of them is guaranteed for the next disease. It had no animal reservoir, so every chain of transmission ran through a person. [2] It produced a rash distinctive enough to be recognised without a laboratory, so a case could be identified by a health worker at a door. There were no long-term carriers, so someone who recovered stopped being a source. A disease missing any one of those is a different problem, and the strategy that worked here would not transfer to it unchanged.
The Counting Was Wrong By A Hundredfold
In 1967 an estimated 10 to 15 million people were infected per year. The reported figure was 132,000. [19] This was not a slightly incomplete count. It was wrong by roughly two orders of magnitude, and every plan built on it was planning against the wrong number. In 1973 a WHO search team found around 10,000 cases in an Indian state that had been reporting about 500 a week. [19]
Estimated infections per year, 1967 [19]
10-15 M
Cases actually reported that year [19]
132 K
Ratio between the two [19]
~100x
What Replaced It
Searching. Reports moving up through a hierarchy of offices arrived late and sometimes altered on the way, [24] so the programme stopped waiting for them and went looking instead. By late 1974 in India some 33,000 district health personnel and more than 100,000 additional field workers were searching house to house across 575,721 villages and 2,641 cities, reaching every one of the country's 100 million households in a six-day period each month. Each nationwide search consumed about eight tons of paper forms. [4] Breman puts the peak figure at more than 150,000 field workers. [3] Both are cited here because both are sourced and they do not agree.
Proving A Negative
Certification did not mean nobody had seen a case. It meant two years had passed with no case detected by a surveillance system judged capable of detecting one had it existed, verified by independent international experts rather than by the programme. [22] That second clause is the whole thing. An absence of reports from a system that could not see is indistinguishable from an absence of disease, which is exactly the trap the 132,000 figure had already sprung once. [19]
The measurement failure and the measurement fix are the same story told twice. Passive reporting could not see 99% of cases in 1967. Certification in 1979 was designed by people who knew that, which is why the standard is about the capability of the surveillance system and not about the case count it produced.
Where The Data Is Weak
Four gaps. The first is the one that matters, because it is about the thing this slate says is solved.
Nobody can prove where all the virus is
The 1980 record says six laboratories were known to retain variola. [2] In July 2014 vials labelled variola and apparently dating from the 1950s turned up in an unused portion of a storage room in an FDA laboratory on the NIH campus, and PCR confirmed variola DNA. [12] The qualifier in the 1980 wording was carrying more weight than it looked. An inventory of declared stocks is not an inventory of stocks.
Mpox surveillance is thin where mpox is
The case counts that show the post-vaccination rise are drawn largely from suspected rather than confirmed cases, in the countries with the least diagnostic capacity. [17] The trend is clear enough to act on and too coarse to measure against. A better-instrumented baseline would change what can be said here.
Population immunity is inferred, not measured
The claim that immunity has lapsed rests on knowing when countries stopped vaccinating and how old people are. [21] This slate cites no serological survey establishing current orthopoxvirus immunity in any population. If one exists it belongs here, and if none exists that is itself the finding.
Emergency response capacity has been measured once
The 2003 United States programme is the only audited attempt at rapid smallpox vaccination cited on this slate, and it reached 6% of its first-stage target by week ten. [18] One data point from one country in one year is what the world knows about its own ability to respond.
The highest-value contribution to this slate would be a sourced answer to the third item. Everything on the still open page about waning immunity currently rests on an inference from vaccination dates rather than on a measurement of people.