A woman working as a poultry slaughtering worker in Boluo country in Southern China's Guangdong province has contracted the dreaded H7N9 avian influenza, prompting authorities to confirm the virus can be transmitted to humans.

Since first being discovered in late March 2013, the novel bird flu strain has infected 134 people and killed 43 in China. The World Health Organization has earlier described it as "one of the most lethal influenza viruses seen so far."

The woman, named Chen and aged 51 years old, became ill on July 27. A day later, she was admitted to a local hospital. On August 3, she was transferred to a hospital in Huizhou City and is now in very critical condition.

People with whom Chen has had close contact with were likewise tested. Although her son gave off a low-grade fever on Friday evening, he tested negative however for H7N9. On early Saturday, his temperature returned to normal. Some 54 other people out of 96 who were in close contact with Chen had been cleared as safe. Health officials however said they all remain under close scrutiny.

Meantime, a recent study published in the British Medical Journal has revealed the virus can be indeed be transmitted between humans.

The study, carried out by Chinese researchers, analyzed the case of a 60-year-old infected father and 32-year-old daughter tandem. It was the father who first became infected with the H7N9 avian influenza because of his exposure to poultry. The daughter only got infected through his oral secretions.

The researchers said they were able to confirm the route of transmission from the index patient through genome sequencing, where the strains from both patients were discovered "almost genetically identical."

Both patients had died.

"To the best of our knowledge, this is the first report of probable transmissibility of this novel virus from person to person with detailed epidemiological, clinical, and virological data," researchers in China wrote. "The importance of an isolated case of such transmission means there is potential for greater human to human transmission. Thus, timely detection as well as rapid investigation and risk assessments of clusters is critically important as the increase in clusters might indicate potential transmissibility of a novel virus."

"The threat posed by H7N9 has by no means passed," James Rudge and Richard Coker of the London School of Hygiene and Tropical Medicine said in a commentary in the same journal.