Incubation period: Time from exposure to symptom development is between 2-14 days.

Prophylaxis and treatment: Currently, there is no approved treatment options in Europe and there is no available vaccine. Avoiding exposure by adhering to recommended hygiene procedures, isolation of COVID-19 infected persons and social distancing are the only prevention strategies (see: Box 1. The WHO recommendations).

EBMT guidelines: Due to fast spreading of COVID-19, panel of experts of EBMT recommends the following guidelines for recipients and donors of hematopoietic cells before the beginning of any of the transplant procedures (mobilization, apheresis, marrow harvest, conditioning). These guidelines will be updated when new information is obtained about COVID-19 epidemiology and clinical outcome.

Recipients:

1. In case of diagnosis of COVID-19: According to ECDC recommendations, patients ought to be deferred for at least three months. However, this is not always possible due to the risk from the underlying disease. Therefore, in patients with high risk disease, HCT should be deferred until the patient is asymptomatic and has three repeated virus PCR negativity at least one week apart. In patients with low-risk disease a three-month HCT deferral is recommended.
2. In case of symptoms of an acute respiratory tract infection (fever, cough or other symptoms attributed to viral respiratory infections), patients shall be tested for respiratory viral infections preferably by multiplex PCR and depending on which virus is detected, deferral of HCT should be considered.
3. In case of close contact with a person diagnosed for COVID-19 any transplant procedures (PBSC mobilization, BM harvest, conditioning) shall not be performed within at least 14 preferably 21 days from the last contact. Patient should be closely monitored for the presence of COVID-19, with confirmed PCR negativity.
4. Stem cell transplant patients should refrain from non-necessary travel to areas designated as high-risk areas by the WHO.
5. In case of travel to a high-risk area or a close contact with person travelling from a high-risk area for COVID-19 (as defined by health authorities*), any transplant procedures (PBSC mobilization, BM harvest, conditioning) should not be performed within at least 14 preferably 21 days from the last contact.

Donors:

1. In case of diagnosis of COVID-19, donor must be excluded from donation. At this time, it is not possible to give recommendations when such an individual can be cleared for donation.
2. In case of close contact with a person diagnosed with COVID-19 donor shall be excluded from donation for at least 21 days. Donor should be closely monitored for the presence of COVID-19.
3. In case of travel to high-risk areas for COVID-19 (as defined by health authorities*) or being a close contact with person travelling from such an area, donor shall be excluded from donation for at least 21 days.
4. Consider cryopreservation of the graft from the unrelated donor at least 21 days before starting the preparative regimen. Request an update information about donor health condition 21 days after cell donation.
5. If possible, ensure that an alternative stem cell source will be available.
6. Donors within 21 days before donation should practice good hygiene (see: Box 1. The WHO recommendations) and avoid crowded places and large group gatherings.