London, April 8 : Two cases of avian flu in a Chinese family have given rise to speculations that the H5N1 virus may have acquired mutations that let it pass from one person to another.
Dr. Yu Wang of the Beijing-based Chinese Centre for Disease Control and Prevention says that a father was probably infected by his dying son in Jiangsu Province last December.
The son was a salesman who was infected by H5N1 avian flu virus when he went to a poultry market six days before falling ill. He was admitted to hospital owing to his constantly worsening condition, where he died five days later.
The doctors believe that his father probably caught the infection while taking care of him at the hospital, for samples of H5N1 virus taken from them were genetically identical, except for one small change.
The father, however, saved survived after being treated with antiviral drugs and blood plasma from a woman who had been deliberately infected with inactive H5N1 in a clinical trial. He spent 22 days in hospital.
Given the rapidity with which flu virus mutates, the researchers believe that the fact that the strains that infected the two men were identical is strong evidence of direct son-to-father infection.
"If we continue to experience widespread, uncontrolled outbreaks of H5N1 in poultry, the appearance of strains well-adapted to human beings might be just a matter of time," Times Online quoted Jeremy Farrar, a doctor at the Hospital for Tropical Diseases in Vietnam, as saying.
A team of doctors identified and followed up 100 close contacts of the father and son for 10 days. Eight of them had been exposed to both men, but none developed H5N1 flu.
The team came to the conclusion that the son passed the infection to his father, probably at the hospital.
They also explored the possibility of the father catching the infection when he visited another market to buy vegetables, where poultry were being slaughtered.
However, the father's insistence that he did not go anywhere near them gives further support to the proposition that he caught avian flu from his son.
In their study report, appearing in the journal Lancet, the researchers have revealed that other cases of suspected person-to-person transmission have also been between blood relations, suggesting that there may be a genetic susceptibility to H5N1 infection.
However, Wendy Barclay, Chair in Influenza Virology at Imperial College London, said: "Although it is possible that the father did catch H5N1 influenza from his son, there is no virological evidence to support the idea that this strain of H5N1 virus has acquired mutations that allow it to pass readily from one person to another."