Scientists trying to gauge the severity of the threat of a swine influenza pandemic face many important knowledge gaps.
Even the death toll from the outbreak, which is thought to have begun more than a month ago in Mexico, and has now spread to several continents, is open to question. Some 150 people have died in Mexico but the number of cases, dead or alive, that have actually been confirmed in the laboratory is much lower at 26 — which means there is little data available for scientists attempting to assess the virus. Read more