There is indeed a worldwide shortage of PPE - totally avoidable, but another discussion
The main risk of transmission is aerosol. The HEPA filters on the AC should provide protection so the risk is to CC within 2M of passengers. ie uncirculated air. The number of asymptomatic patients (those infected but not ill but shedding virus) has been low but is now 2-5% in the UK possibly reaching 10% next week. This is no longer negligible and at long last most healthcare systems are starting universal precautions ie assuming everyone is positive
NO flights should still be happening but there are repatriation flights and if it was up to me I would recommend coveralls, FFP3 masks and goggles and gloves. There is no evidence the risk to cc is that much less than to healthcare workers......However they need to be trained and it will not be easy to doff on board so long haul flights will be difficult
The one thing that is clear is that ordinary surgical masks are effectively useless unless a passenger actually sneezes in your face.
Aircrew are only at risk from each other plus the difficulty of getting airside - airports have some of the highest risk of all. But no PPE is sensible on the flightdeck