Experts still unclear over how illness spreads

SCIENTIFIC VIEW:A LEADING Irish influenza expert said it was unclear how easily the swine flu spread between humans and too early to predict whether it would lead to a global pandemic.

Luke O’Neill, professor of biochemistry at Trinity College, said the World Health Organisation’s decision to upgrade its alert level to five, the second-highest, was precautionary and designed to make countries stock up on antiviral drugs and activate their pandemic “preparedness” plans.

The ease with which the virus spread between humans had yet to be established, he said, and there was still a chance human-to-human infections were “unusual in some way”, or resulted from contact with highly infected people.

Speaking at a briefing on the virus at TCD’s science gallery yesterday, Prof O’Neill said the scientific community was “very much in the early stages of the understanding the virus” and there had only been nine confirmed deaths directly as a result of the flu.

He said a significant number of human-to-human infections would have to be confirmed before the WHO raised its alert level to six, which would indicate a full-blown pandemic.

Prof O’Neill said there was growing concern that young healthy adults appeared to be succumbing to the virus in greater numbers, a phenomenon observed in the 1918 Spanish flu pandemic which is estimated to have killed more than 20 million people.

Usually the elderly and very young are most vulnerable because their immune systems may be impaired or underdeveloped. One theory is that this flu may be causing the immune system in otherwise healthy people to overreact and destroy lung tissue, causing a type of “collateral damage” in the body, said Prof O’Neill. “It’s possible that a very strong immune response to the virus is what actually kills people.”

However, the outbreak may be contained as the virus appeared to respond well to antiviral drugs such as Tamiflu, provided it was administered soon after the onset of symptoms.

The main worry would be if the virus mutated into a more virulent form and started to kill people quickly, “so it is essential that we have a vaccine ready for that eventuality”, said Prof O’Neill.

TCD’s professor of experimental immunology, Kingston Mills, said there was still no clear explanation as to why all the fatalities, with the exception of a two-year-old boy who died in Texas on Monday, had been confined to Mexico. Viruses often become more virulent as they evolved “but it may be the reverse in this case”.

The people who died in Mexico may have come into direct contact with animals and contracted a more virulent form of the virus.

“Those who are getting it from other humans may be getting a milder version,” Prof Mills added.

It is also possible that the victims in Mexico may have had other underlying infections such as tuberculosis, HIV or Hepatitis C, which are more prevalent there.

More worryingly, it may be the case that “we haven’t begun to see what the effect of the virus is in countries, like the US, because it has only been there a short time”.

Prof Mills said many scientists believed the virus may have been in Mexico for several months before it was identified. It would take between three to six months to develop a vaccine because of the laborious procedure involved.