Why the timeline is organized by nodes
An outbreak timeline is more useful when it follows evidence changes rather than every calendar day. The practical question is whether the situation changed and whether that change affects a country, travel history, or close-contact group. For that reason, each step here is a case discovery, clinical event, public-health notification, evacuation node, or country signal. A node can share the same date as another node, but it still matters if it changes the interpretation of the map.
The first important distinction is between likely exposure, illness onset, and confirmation. WHO's account of the MV Hondius event says the first probable case boarded on 1 April after more than three months of travel in Argentina, Chile, and Uruguay. That matters because WHO's working hypothesis is not that the virus magically began in the middle of the ocean. The hypothesis points toward probable environmental exposure before boarding, especially in Argentina. The map begins with land-based exposure context and a boarding investigation point, then shows the ship-linked cluster as the event that carried the public-health response forward.
The next distinction is between a case's location and the location where the evidence became visible. Case 2 became medically important around the St Helena and Johannesburg part of the story; Case 3 was also medically evacuated and hospitalized in Johannesburg. These are not signs of South African community spread. They are medical destination and response nodes. The timeline explains what the marker means before a country marker is mistaken for a local outbreak.
By early May, confirmation and notification changed the situation again. WHO says the United Kingdom notified WHO through the International Health Regulations about severe respiratory illness aboard the Dutch-flagged ship, including deaths and a critically ill passenger. WHO later reported a baseline of eight cases, including three deaths, with six laboratory-confirmed Andes virus infections. That is the central official baseline. Reputable media reports after that baseline may still be important, but they are not silently merged into official counts without a label.
Country signals near the end of the timeline are different from the early clinical nodes. Spain, the United Kingdom, Canada, Ireland, Turkey, Japan, Australia, France, and the United States each enter the event story for different reasons. Some represent quarantine or isolation reporting. Some represent passenger nationality. Some represent reported positive tests after evacuation. The evidence class identifies whether a country is confirmed, watch, media-only, or low known risk.