Two of the three Fatima children were dead within three years of the apparitions, and the thing that killed them killed a very large number of Portuguese people in the same months.
The pandemic in Portugal
The influenza pandemic of 1918 and 1919 reached Portugal in the summer of 1918 and moved through the rural interior in the autumn. Country parishes had almost no medical provision. In hamlets like Aljustrel the disease went through whole households at once, and the Marto family was one of the households it took.
Francisco
He fell ill in the autumn of 1918, recovered enough to be moved about the house, weakened again over the winter, and died on 4 April 1919 at Aljustrel, ten years old.
Jacinta
She was ill at the same time and did not recover. The infection settled in her chest and became a purulent pleurisy. She was taken to Lisbon, operated on, and died in hospital on 20 February 1920, nine years old, away from her family.
Why it matters to the account
The apparitions are said to have included a statement that two of the children would be taken soon and the third would remain. The difficulty is dating that claim. It reaches us through the memoirs Lucia dos Santos wrote from the 1930s onward, after both of her cousins were dead, and there is now no way to establish what was being said about it in 1917. That is not an accusation against anyone. It is the ordinary problem with the Fatima record, which is a record of what one surviving witness recalled rather than a record of the events.