Evidence ledger

The map is only as trustworthy as its source classes.

The ledger separates official case evidence, reported positives, monitoring signals, media-only leads, duplicates, and corrections.

Embedded evidence map

The same geography can mean different things depending on evidence class. The ledger explains the source basis behind each marker.

Why an evidence ledger matters

Many outbreak maps are easy to copy. A marker, a dark background, and a few alarming numbers can be assembled quickly. What is harder to copy is evidence discipline. A defensible hantavirus map needs to show why each marker exists, whether it changes the confirmed count, and what source would be required to promote or downgrade it. That is the reason this evidence ledger is not optional content. It is the trust layer that makes the live map worth returning to.

The highest evidence class is an official health source. For the MV Hondius event, the WHO Disease Outbreak News item is the central source because it gives the official case baseline, the clinical summaries, the deaths, and the risk framing. It also explains the likely exposure investigation and the difference between ship risk and general public risk. If a marker or number conflicts with WHO's baseline, it is either excluded or labeled as a later reported update.

The next class is national or local health authority information. These sources matter for local risk because imported cases, quarantine instructions, and contact tracing are often published by the country handling the passenger. A country health authority can upgrade a local risk card from watch to confirmed imported case. It can also downgrade a rumor by stating that no local case has been identified. Those statements carry more weight than general aggregation.

Reputable media is the third class. It is valuable because journalists may report evacuation, repatriation, or positive tests before a public-health page is updated. But media reports need labels. If a Guardian article reports that an American and a French passenger tested positive, the map can show those as reported positive passengers, while keeping them separate from the earlier WHO baseline. That label protects the count from inflation.

Manual leads and competitor entries are the weakest public class. They can help identify where to look next, but they do not automatically become public case counts. A competitor sidebar may list suspected entries in many countries. Some may be useful clues; others may be duplicates, unverified contacts, or vague location notes. Low-confidence leads stay away from confirmed totals and carry an explanation of their weak status.

How the ledger prevents bad data

The main failure mode of a live map is duplicate inflation. If ten articles repeat that three people died, the death count is still three, not thirty. If multiple outlets mention a Spanish quarantine group, the group does not become multiple groups unless the source clearly identifies new people. If a suspected case later becomes confirmed, the same record changes status rather than becoming a second record. This is basic, but many fast maps fail here.

The second failure mode is category confusion. Monitoring is not infection. Passenger nationality is not local transmission. A medical destination is not community spread. A ship route is not an origin by itself. The ledger gives every row a count basis and relation statement so a map marker does not carry more meaning than the evidence supports.

The third failure mode is stale data. A tracker can say "live" while actually using a curated seed dataset. That is acceptable only with clear labeling. The current dataset is manually curated event intelligence, not automated live surveillance. If automated source checking is added later, the ledger can show last checked time, source result, and whether a change was accepted, rejected, or held for review.

Corrections are part of the evidence chain. A corrected suspected case, a duplicate media mention, or a downgraded country signal remains understandable after the fact. A map change can come from a new official source, a superseded old source, or removal of a weak lead. That transparency keeps trust during a fast-moving story.