* Nasal swabs currently main source for tests in Japan
* New tests will reduce burden on patients, testers -health min
* New tests available for those with symptoms for up to 9 days
* Daily Tokyo infections topped 30 for first time in 19 days - NHK 

Japan on Tuesday approved saliva-based tests for the coronavirus, offering a safer, simpler way to diagnose infection than nasal swabs as it looks to boost its testing rates. Hours after the approval, the Tokyo government issued a stay-at-home alert following an increase in infections.
Currently, nasal swabs are the main source for tests in Japan, but these can expose medical workers to coughs and sneezes at the time of collection, making it necessary for them to wear full protective gear.
The saliva-based tests are able to be given to those who have had symptoms for up to nine days, the health ministry said. It wasn't immediately clear how much the change would boost overall testing capacity.
"This will vastly reduce burdens on patients as well as burdens that come with infection-prevention steps on the part of sample-collecting institutions," Health Minister Katsunobu Kato told reporters.
Japan falls well behind other industrialised nations in terms of its number of coronavirus tests. Critics say the low rate of testing has made it difficult to trace the virus, which has led to a series of in-hospital infection clusters.
As of May 20, Japan conducted 3.4 PCR tests per 1,000 people, far below Italy's 52.5 and 39 in the United States, according to Oxford University data. South Korea has carried out tests on 15 people per 1,000 people.
Japan, which lifted its state of emergency last week, has escaped an explosive outbreak, with nearly 17,000 infections and 898 deaths so far, according to NHK public broadcaster.
The Tokyo government issued an alert urging people to stay at home for non-essential business and to practise social distancing after 34 new infections on Tuesday, the most since May 9.
The health ministry said about two dozen different test kits, including one from Takara Bio Inc, have been approved for saliva-based PCR tests. Shares in Takara Bio jumped 4% on Tuesday.
Musashino Central Hospital in western Tokyo said 12 patients and three hospital workers had been confirmed with the virus, taking the total number of cases at the hospital to 31, forming the latest infection cluster.