CAIRO — Heshmat Youssef used to make a decent living sailing foreign tourists down Egypt’s Nile River. Since political unrest flared, business has dried up faster than water in the desert.

Riots and killings that spiked after the Aug. 14 crackdown against followers of ousted President Mohammed Morsi have delivered a severe blow to Egypt’s tourism industry, which until recently accounted for more than 11 percent of the country’s gross domestic product and nearly 20 percent of its foreign currency revenues.

The chairman of the Egyptian Airports Company, Gad el-Karim Nasr, said arrivals at Egyptian airports have dropped by more than 40 percent from Sunday through Tuesday compared to the same time the previous week. He said that in the same time-frame, 13,000 tourists, mostly from Germany and Italy, have left the Red Sea resorts of Sharm el-Sheikh and Hurghada — with only 3,000 new arrivals.

With governments in the U.S. and Europe advising their citizens to avoid Egypt, the impact threatens the livelihood of the one in eight Egyptians who earn their money from tourism.

“We want to live in stability and for tourism to come back,” said Youssef, who hasn’t seen holidaymakers in weeks. “Let us eat already. We are extremely tired.”

The latest shock occurred just as Egypt’s tourism industry, which injected more than $10 billion into the economy last year, was slowly recovering from the blow suffered from the 2011 uprising against ousted President Hosni Mubarak.

That uprising had already prompted some U.S. operators to pull out of Egypt.