Russia has responded to concerns about a possible plague outbreak after a laboratory worker died in the Irkutsk region of eastern Siberia. It has said it was an isolated incident confined to the lab and posed no threat to the public. However, the US has called for more transparency in the matter, prompting international debate.

Russia's health watchdog Rospotrebnadzor has dismissed the reports. It said in a statement on Wednesday that there was no risk of infection for the people of the Irkutsk region. It said that medical tests had been carried out on those who had been in close contact with the deceased worker, and none had shown signs of infection or dangerous pathogens. It said that precautionary and preventive measures had been fully implemented and that the World Health Organization (WHO) had been informed of the situation.

Kremlin spokesman Dmitry Peskov also responded to the matter. He confirmed that the WHO had been informed last week in accordance with the rules. He accused some media outlets of spreading false information. The US has lodged a diplomatic complaint seeking more transparency over the incident. He said that only official statements should be trusted.

According to a local TV channel in Irkutsk, the woman died on October 2 in a hospital in the town of Shelekhov. The hospital was immediately quarantined and those who had been in close contact with her were put under observation. Officials announced that none of them had developed symptoms of plague as of Tuesday.

World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus also confirmed this. He said that Russian authorities had informed him that no cases of plague had been recorded in the region. The WHO had previously assessed that the risk of the disease spreading outside Russia was very low. Russian authorities described the deceased's illness as a common "respiratory viral infection".

On the other hand, the US expressed concern over the incident. US Secretary of State Marco Rubio said that the available details were very limited and it was unclear whether the condition was minor or serious. He urged Russia to share more information. 

The incident is reminiscent of the debate over the origins of Covid-19. Unlike bubonic plague, which is usually spread by rodents, pneumonic plague, which is spread from person to person through respiratory droplets, is the most dangerous. It is against this backdrop that international concerns have been expressed.