AZ Alkmaar have been hit by 13 positive coronavirus cases, but their Europa League clash with Napoli on Thursday will still go ahead as planned.
The Dutch side had already confirmed that eight players would be unavailable for the trip to Napoli after they tested positive for Covid-19, and on Tuesday afternoon it was announced that a further five in their squad had been diagnosed with the virus.
The players who have returned positive tests have not yet been named, but will be revealed when AZ make the trip across Europe to Italy to kick-start their Europe League campaign on Wednesday.
The positive cases leaves boss Arne Slot with just 17 available players to choose from.
Despite the high number of infections, AZ insisted their opening Group F match with Napoli will still be played, although local authorities could prohibit the match from going ahead.
A statement released by the club on Tuesday read: 'AZ has carefully followed the applicable procedures in recent months. The majority of the positively tested players show no symptoms.
'Because infections were detected during the selection, AZ took preventive action and carried out additional tests, among other things, so that the cases now demonstrated could be detected.
'Last week, nine people tested positive, three of them have now tested negative.
'AZ is scheduled to play Napoli. This match will continue, according to UEFA, unless the local authorities prohibit it.'
Earlier this month, health authorities in Naples - known as ASL - stopped the Serie A club from travelling to Turin to face Juventus due a Covid-19 spike.
Napoli were given a one-point deduction and forced to forfeit the game, handing Juventus a 3-0 victory after they failed to fulfill the fixture.
The Serie A giants have however submitted an appeal to The High Court of Sports Justice and reports in Italy claim they are optimistic of the Italian Football Federation's decision being overturned and replaying the game against Juventus at a later date.