Person-to-person bird flu transmission scare

You may want to remain alert for bird flu as a new study has provided an evidence of probable transmission of the avian influenza virus between two unrelated individuals.

Previous reports of person to person transmissions have all occurred in family clusters, suggesting that either common exposures or genetic susceptibility might contribute to the infection. However, the new study describes two patients who shared the same ward in a district hospital in Zhejiang Province.

The first (index) case was a 49 year old man, who was diagnosed with H7N9 virus on 24 February and was admitted to a specialist hospital ward with intensive care facilities. He died of multi-organ failure on 20 April.

The second case, a 57 year old man with a history of chronic lung disease (COPD), developed flu-like symptoms after staying on the same ward of the district hospital as the index case for five days (18 to 23 February). He was diagnosed with H7N9 virus on 25 February and died of respiratory failure on 2 March.

The second patient had no history of poultry exposure for 15 days prior to his illness. Samples from his home, from chickens raised by his neighbours, and a local chicken farm were all negative for H7N9 virus.

Yet the genetic sequence of H7N9 virus from the second patient was nearly identical to that from the index patient, and genetically similar to the virus samples taken from the live poultry market visited by the index patient.

The researchers stress that they cannot completely rule out an unidentified environmental exposure that might explain the H7N9 infection in the second patient.

However, because no other common exposure was identified, they say it seems most likely that the H7N9 virus was transmitted from the index case to the second case during their stay on the same ward.

They say these results should raise our concern about the increasing threat to public health and they call for better training and hospital hygiene as well as enhanced surveillance of both patients with influenza-like illness in hospitals and chickens in live poultry markets.

"We must remain alert for (re)emerging infections, including avian influenza, particularly when we still cannot tell how risks to humans will evolve. We also need to invest more in clinical, epidemiological, and virological research to unravel the risks posed by sporadic human infections with any avian influenza virus," they conclude.

The study appears in The BMJ.