* Japan to start trials 'as soon as possible' - govt spokesman
* Total infection cases at 520, most from cruise liner
* US, other countries evacuating nationals from Diamond Princess
Japan plans to trial HIV medications to treat patients infected with coronavirus as its growing number of cases poses an increasing threat to the economy and public health, the government's top spokesman said on Tuesday.
The government was making "preparations so that clinical trials using HIV medication on the novel coronavirus can start as soon as possible," Yoshihide Suga told a briefing, but added he could not say how long a new drug would take to be approved.
Japan had 520 confirmed infections by Monday, including 454 cases from the Diamond Princess cruise ship quarantined off the port of Yokohama, the health ministry said, with one death from the virus.
On Tuesday, there was three more cases confirmed with the virus in Wakayama Prefecture, local media reported.
As the contracting economy fuels a risk of recession, the spread of the virus has prompted Tokyo to put limits on the size of public gatherings while some companies are telling employees to work from home.
The HIV trials come as those drugs have been touted as a potential cure for the coronavirus around the world. With no therapy yet proven 100% effective, the epidemic has killed close to 1,900 people in mainland China.
People in China have begun exploring unorthodox ways to get treated, with some appealing to HIV patients and unauthorised importers for medicine.
In Thailand, doctors said they appeared to have had some success in treating severe cases of the virus with a combination of medications for flu and HIV.
As demand for masks skyrockets, police are investigating a theft of 6,000 surgical masks reported by the Kobe Red Cross Hospital in the central Japanese city, a hospital official told Reuters.
Japanese officials have vowed to work hard to avoid disruptions to the Olympic Games, which start in Tokyo in July. But growing concern over the virus spurred Mongolia's Olympics archery team to cancel training in Japan, the Kyodo news agency said.
On Monday, US government evacuation flights flew home more than 300 Americans who had been on the Diamond Princess cruise ship.
With more than 3,000 passengers and crew, the ship has been in quarantine since early this month, after a passenger who had left it in Hong Kong was diagnosed with the virus.
About half of those aboard are Japanese and the rest foreign nationals, many of whom have expressed frustration over the quarantine.
The liner will receive meals from World Central Kitchen, a non-profit set up by celebrity chef Jose Andres, in a bid to reduce the burden on crew, said Rai Caluori, vice president of vessel operator Princess Cruises.
Foreign governments including Australia, Canada, Italy and South Korea also plan to take citizens off the cruise liner.
A plane chartered by the Canadian government has left for Japan to evacuate its nationals, TV Asahi said. Canada has said 14 days of quarantine await them on their return.
South Korea is also sending a government charter flight on Tuesday to take home four citizens, and a Japanese spouse, who have no symptoms, a South Korean official said.
Japanese who test negative will begin disembarking as early as Wednesday, health minister Katsunobu Kato said.
"Everyone wants to return home as soon as possible, so considering that feeling, we are making preparations," Kato told reporters.
Disembarkation was set for Feb. 19 to 21, Japan's vice health minister said, according to a copy of a letter circulated on Twitter by a passenger using the handle @daxa-tw.
The letter told passengers that Yokohama health authorities would take their temperatures before they left the ship.
Japan's health ministry could not immediately be reached for confirmation.