0:00:00.299,0:00:05.130
Con il susseguirsi della pandemia, [br]la preoccupazione ricade sulle varianti,

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di cui numerosi esempi[br]rilevati in Sud Africa,

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Brasile e Regno Unito.

0:00:10.320,0:00:12.943
Ma le varianti sono complicate.

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Ogni variante si crea [br]da un insieme di mutazioni,

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ciascuna delle quali [br]potrebbero variare il virus SARS-CoV-2

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in modi imprevedibili.

0:00:22.379,0:00:26.030
Quindi cosa si intende [br]quando parliamo di varianti?

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E cosa potrebbe significare[br]per il futuro della pandemia?

0:00:30.854,0:00:34.828
I virus si moltiplicano [br]copiando ripetutamente i loro genomi.

0:00:34.828,0:00:38.953
Ma come una vecchia fotocopiatrice,[br]le copie non escono sempre perfette.

0:00:38.953,0:00:42.286
Ogni copia imperfetta è una variante.

0:00:43.120,0:00:47.376
Normalmente le imperfezioni o le mutazioni[br]non cambiano il comportamento del virus,

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e spesso lo rendono[br]meno efficace del ceppo originale.

0:00:51.610,0:00:54.541
Ma di rado, le mutazioni[br]possono variare il virus

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in maniera molto importante.

0:00:56.431,0:00:58.565
Possono renderlo più contagioso,

0:00:58.565,0:01:01.742
o più capace di evitare [br]il sistema immunitario.

0:01:03.109,0:01:06.000
Più un virus si replica senza controllo,

0:01:06.000,0:01:09.987
maggiori sono le probabilità [br]di queste rare mutazioni.

0:01:10.560,0:01:12.065
Può succedere quando il virus

0:01:12.065,0:01:14.948
si diffone velocemente[br]attraverso una popolazione,

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o quando incontra un ospite[br]con meno capacità di combatterlo,

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come le persone con un sistema immunario[br]compromesso da cure mediche

0:01:22.287,0:01:24.597
o chi ha l'HIV+.

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