Mar 20, 2007 (CIDRAP News) – Hong Kong officials have reported that a 9-month-old girl is infected with the strain of avian influenza known as A/H9N2, which has caused mild human illness in the city three times before and is considered capable of evolving into a pandemic strain.

The Hospital Authority in Hong Kong said the baby girl has only mild symptoms but is in isolation at Princess Margaret Hospital, according to an Agence France-Presse (AFP) report today.

Thomas Tsang, head of the Hong Kong Centre for Health Protection, said test results today confirmed that the virus is H9N2, according to the story.

The same strain infected two girls in Hong Kong in 1999 and a 5-year-old boy there in 2003; all had mild illnesses and recovered.

Tsang said the baby girl became ill Mar 4 with an upper respiratory tract infection and fever and was hospitalized at United Christian Hospital from Mar 6 to 9, AFP reported. The story did not make clear when she was admitted to Princess Margaret Hospital.

The Hospital Authority said it was "very concerned" about the case and that United Christian Hospital would "conduct a review" of all healthcare workers who had close contact with the girl, according to AFP.

A report from Deutsche Presse-Agentur (DPA) today said the girl was believed to have contracted the virus from a market in a densely populated area of Hong Kong.

The AFP report quoted Tsang as saying in a statement, "Further genetic sequencing is being conducted to determine if the virus is completely of avian origin. This is an isolated case and the source of infection is being investigated. Based on previous experience, however, we will look especially into bird-to-human transmission."

The Centre for Health Protection said the girl"e;s family members were well and she had not been taken outside Hong Kong recently, according to AFP.

In 2004 the US National Institute of Allergy and Infectious Diseases (NIAID), concerned that H9N2 could evolve into a pandemic strain, contracted with Chiron Corp. (now part of Novartis) to produce a vaccine against the virus. Last September scientists reported that the experimental vaccine generated a good immune response in a phase 1 clinical trial.

The contract called on Chiron to make 40,000 doses of the vaccine, based on an inactivated strain of H9N2 developed by the Centers for Disease Control and Prevention.

The report on the clinical trial results said H9N2 viruses are widespread in Eurasian poultry. Two of the three different Asian lineages of these viruses can bind to human as well as bird cell receptors (sialic acid residues) and therefore may be more likely to infect humans than other avian flu viruses are, the authors wrote.

The H9N2 strain of avian flu is distinct from the lethal Asian strain of H5N1 virus, which has killed millions of poultry in Asia, Africa, and Europe and caused 281 human illness cases, 169 of them fatal, according to the World Health Organization"e;s current tally.