Everything you wanted to know about swine flu
John McConnell, an editor at The Lancet and founding Editor of The Lancet Infectious Diseases, is answering questions about the swine flu:
What is the science behind how new flu strains arise – this one has pig, human and bird components (mainly pig). How has it got this way and how is it able to gain each of these components?
The basic science is explained on Wikipedia’s pandemic page in the epidemic and pandemic spread section. Quite how the current swine H1N1 acquired its genetic elements might take a while to work out and may never fully be understood
Is there anyone who can talk about the discrepancy in the numbers – why is the testing taking so long? Are they re-testing samples? Someone who could give us a perspective on where we are up to with this
Testing isn’t taking a long time. There are only a limited number of laboratories around the world that have the expertise to do virological typing. In the long term, if the epidemic spread and cases become more numerous, it is likely that only a limited number of suspected cases will be confirmed by typing.
We are interested in how long it will take to come up with a viable vaccine for this particular strain of flu, and how long after that it could be massed produced.
I’d estimate 4-6 months to produce sufficient vaccine for a national population-wide immunisation programme … A decision to produce vaccine against H1N1 would not necessarily come at the expense of the seasonal flu vaccine, but we have nothing like the capacity to vaccinate the whole world’s population and, as always, the poorest and most vulnerable people will be last in the queue for vaccine.
We also are interested in the genomutability — if that’s the correct term — of this strain; quite how much potential does it have to alter as it spreads.
The flu virus is unstable and unpredictable. If anyone knows the answer to this question please let me know. However, there is no evidence that the virus will cause more serious disease as it spreads. If anything, disease morbidity is more likely to decrease in the long-term as population-wide (herd) immunity increases.
I’m also getting asked by the news editor whether this is all hype. Someone who can shed light on that would be very useful!
No, it’s not all hype. My feeling, based on what we know so far, is that estimates of tens of millions of deaths are hype, but what we might see is a pandemic of relatively mild illness similar to the 1968 pandemic. The 1968 pandemic caused by the H3N2 flu virus is estimated to have caused an excess mortality of around 1 million people—ie, equivalent to the mortality of about two annual flu seasons. However, I am definitely not predicting 1 million deaths from H1N1 because there is insufficient evidence on which to base a prediction.
I am still looking at why there are deaths in Mexico and not elsewhere. The CDC says there are hospital admissions there and they expect deaths so does this support the ‘iceberg’ theory that we were only seeing the worst cases reported in Mexico and if there are sufficient cases elsewhere we will see deaths there too.
Every year, seasonal flu causes 250 000-500 000 deaths in vulnerable, and otherwise healthy, people. So it is likely we will see deaths outside Mexico from H1N1. Indeed, the death of a 23-month-old child in Texas was reported this morning. Many mild cases may have gone unreported in Mexico, which, if this is the case, means that the death rate in Mexico is not as high as it appears to be.