Sources and methods

This page explains where our information comes from, how we decide what to publish, what the three labels on our claims mean, and how we fix mistakes. It applies to every page on PlaguePrimer.

What we cover

We cover one event, the suspected plague case reported in Irkutsk, Russia, in early October 2026, and the public health ideas you need to follow it.

• The full story and the timeline track what has been said about the case, and by whom.
• The Plague explained pages cover how plague and other infections spread and how outbreaks are contained, using plague as the example.

Which sources come first

We rely on sources in this order:

1. The World Health Organization (WHO).
2. National and regional health authorities. For this event that mainly means Russia's public health agency, Rospotrebnadzor. For background we also use agencies such as the US Centers for Disease Control and Prevention (CDC) and the European Centre for Disease Prevention and Control (ECDC).
3. Peer-reviewed research in medical and scientific journals.
4. News organizations that publish under their own name, such as international wire services.

We name the source in the sentence and link to it. For example: "WHO said on [date] that…". When we can find the original statement, we link to it rather than to a page that repeats it.

Rospotrebnadzor and other Russian authorities publish in Russian. When we can find the original, we link it, summarize it in English and translate any quote ourselves. When we can't, we link the named news organization that reported it and say so in the sentence. For example: "Rospotrebnadzor said, as quoted by Interfax, that…".

We don't treat anonymous social media posts, forums or unsourced videos as evidence. If a claim from those places is spreading widely, we may mention it, labeled Unconfirmed, to tell you that we could not verify it.

How we label claims

On the home page, the full story and the timeline, each claim about the Irkutsk case carries one of three labels. A label tells you how solid the source of a claim is. It does not describe the state of the case.

Confirmed

the health authority's own statement, or 2+ independent outlets

Reported

one outlet only, an unnamed or non-health official, or a preliminary detail

Unconfirmed

circulating, we could not verify

What counts as each:

• Confirmed. A health authority, such as WHO, Rospotrebnadzor or another national or regional health agency, has stated it on the record, and we can show it in one of two ways: we link to the authority's own statement, or at least two independent named news organizations report it. Independent means each has its own account of the statement, not one repeating the other.
• Reported. It appears in reports by named news organizations or in official notices, but doesn't meet the bar for Confirmed. This includes a health authority's statement that only one news organization has reported, reports that quote unnamed officials, and details that officials describe as preliminary.
• Unconfirmed. It is circulating, but we could not trace it to a health authority, an official notice or a named news organization. We include it only when it is widely shared, to say that it is not verified.

How we apply them:

• Confirmed means a health authority said it, not that it can never change. If an authority revises a statement, we update the claim and note the change in the timeline.
• When a claim moves from one label to another, for example from Reported to Confirmed, we change the label and add a dated entry to the timeline.
• When sources disagree, we show each version with its source and date, and say that they disagree. We don't pick a side unless a health authority settles the question.
• Until a health authority confirms the cause, our headlines call the case "suspected".

The state of the event itself, such as "Under investigation", is written in plain words in the status line at the top of the home page, the full story and the timeline, with an "as of" date. All three pages show the same status line, and the labels are never used for it.

How we date pages

• Checked: every explainer and event page shows the last date we re-read the sources behind it and confirmed the page still matches them. A page can be checked without being changed.
• Updated: when we change what a page says, its updated date changes too.
• Timeline entries are dated by when the source published the information.
• Policy pages like this one show a "Last updated" date.

What we don't do

• We don't forecast case numbers, spread, or the outcome of the investigation.
• Figures on our explainer pages, such as typical incubation periods for plague, come from WHO, CDC or published research and are dated. They describe plague in general. They are not estimates for the Irkutsk case.
• We don't give personal medical advice. See our medical disclaimer.
• Our pages are not reviewed by a practicing clinician. We don't describe them as medically reviewed.
• We don't publish the names or personal details of patients, health workers or their contacts, even when they circulate online.

Corrections policy

If we get something wrong, we fix it and say so.

• Factual errors. We correct the page and add a note in the "About this page" box at the foot of the page, saying what changed and on what date.
• Changes to a conclusion. If a correction changes what we say about the Irkutsk case, for example what has been confirmed, we also add an entry to the timeline.
• Small fixes. Typos, broken links and wording changes that don't change the meaning are fixed without a note.
• We don't remove a correction note once it has been published.

To report an error, write to support@plagueprimer.com. Please include the page address, the sentence you think is wrong and, if you can, a source. We read every report. We may not reply to each one, but corrections appear on the page itself.

Image sources

All photos on this site are in the public domain and credited below. Diagrams are our own and are simplified on purpose.