BELFAST, Northern Ireland — Hand-washing is the first line of defense against COVID-19 and many other diseases. Yet 1 in 4 health care centers around the world has no hand-washing facilities, and in the lowest-income countries, almost half have no clean water. A lack of facilities means over 2 billion people are forced to seek care in a place where there is no clean water and 1.5 billion people visit health care facilities with no sanitation services at all. Advocates say that needs to be understood in order to help low- and middle-income countries control the virus. “The vital role of good hygiene in preventing hospitals [from] becoming breeding grounds for disease is being woefully overlooked as part of the global response to COVID-19,” said Tim Wainwright, chief executive of WaterAid. In a statement for WaterAid, Rhoda Phandama, a nurse and midwife in Malawi, added that the Katimbira Health Centre in Nkhotakota, where she works, doesn’t have enough soap.