* Existing unit in Monrovia overflowing, new ward delayed by protests
* Liberia faces "humanitarian crisis" - assistant health minister
* U.S. charity fighting virus withdraws non-essential staff
By David Lewis
DAKAR, July 30 (Reuters) - An isolation unit for Ebola victims in Liberia's capital, Monrovia, is overrun with cases and health workers are being forced to treat up to 20 new patients in their homes, government officials said on Wednesday.
Protests by the local community against the construction of a new isolation unit at Elwa Hospital have ended, said Tolbert Nyenswah, an assistant minister of health, but patients with Ebola symptoms will have to wait at home until work is finished.
West Africa is battling the worst Ebola outbreak on record, with 672 people believed to have died in Liberia, Guinea and Sierra since the epidemic began in February, according to the World Health Organisation.
"The staff here are overwhelmed. This is a humanitarian crisis in Liberia," Nyenswah told Reuters by telephone. "People are being given care at their homes until we can move them to the new unit."
Nyenswah said the suspected patients were being treated by trained medical staff with full protective gear, but it would take at least 24-36 hours to build the new unit.
Initial resistance to building a new isolation unit highlighted the fear and mistrust health workers have faced across West Africa as they battle the outbreak, which has strained the region's weak health systems.
Dozens of local health workers have died treating patients and two Americans working for Samaritan's Purse, a U.S. charity operating in Liberia, were infected over the past week.
Samaritans Purse said on Wednesday that Kent Brantly, a doctor working for Samaritan's Purse, and Nancy Writebol, a colleague who was also volunteering in Liberia, had shown a slight improvement but were still in serious condition.
The organisation said that it was withdrawing non-essential staff from the country because of instability and security issues. (Editing by Daniel Flynn, Larry King)