Three laboratories in Democratic Republic of Congo have run out of supplies to test for Ebola, the World Health Organization said, as the outbreak of the dangerous Bundibugyo species of the virus continues to grow.

In the latest situation report, dated June 7 and released on Tuesday night, the agency said laboratories in Bukavu and Lwiro in South Kivu province, and Goma in North Kivu, had run out of stock. It said that the labs were awaiting the arrival of reagents - substances required to run the tests - to resume work on backlogged samples.

The WHO did not immediately respond to requests for comment about how many samples were awaiting testing.

There have been almost 600 confirmed cases in the Ebola outbreak and more than 115 deaths, the Congolese government announced on Tuesday evening.

Cross-border fatalities

There have also been 19 cases and two deaths in neighbouring Uganda linked to the epidemic, which the WHO has declared an international public health emergency.

Testing began slowly because the widely available Ebola tests did not immediately detect the Bundibugyo virus.

The outbreak continues to spread and has now affected 25 health zones in the provinces of Ituri, North Kivu and South Kivu.

According to health authorities, the outbreak caused by the Bundibugyo strain of the Ebola virus remains on an upward weekly trend. They said a recent slight decline reflected in the epidemic curve may be linked to delays in laboratory data updates.

Surveillance activities, case management and community awareness efforts continue in affected areas, the ministry said.