The National Health Board of Denmark has announced the first known case ofpandemic H1N1 flu resistant to the antiviral drug Tamiflu. They stress, though, that "there is no evidence" that the virus has spread.
The case is likely to be isolated, but calls into question the policy in most European countries of giving low doses of Tamiflu to people in contact with infected people. The Danish case, a contact of someone who caught swine fluabroad, was given Tamiflu as prophylaxis to prevent her getting sick, but she developed symptoms anyway.
She then took Relenza, another antiviral drug, and recovered. The State Serum Institute in Copenhagen found that her virus carried a mutation giving resistance to Tamiflu, and assumes this emerged during treatment rather than having been there already.
"Such a development is no surprise from a scientific point of view," said David Reddy, head of the pandemic taskforce at Swiss company Roche, which produces Tamiflu. Like antibiotics, antiviral drugs favour the survival of strains that resist the drug.
Despite this, H1N1 viruses that resist Tamiflu are quite capable of spreading. The normal seasonal H1N1 virus became almost entirely Tamiflu resistant over the past two years, for reasons that are not yet understood. Scientists fear the pandemic virus, also a member of the H1N1 family, might acquire Tamiflu resistance by interbreeding with these ordinary strains.
It might also evolve resistance by exposure to the drug. Denmark has had only 37 known cases of the pandemic flu so far, so it is still trying to limit the virus's spread by giving Tamiflu to contacts of cases. Once the virus is spreading widely, such efforts to limit the spread of individual cases are abandoned as pointless.
Other scientists warned this month that "it is not yet clear whether large-scale prophylaxis is justified, given the potential risks of high-level resistance developing". Prophylactic doses are half those used for treatment, and such low doses can favour the emergence of resistant strains.
We have stocked Tamiflu antiviral at home. Ideally within 6 hours and at the very latest within 48 hours of flu symptoms we will commence Tamiflu treatment. I bought Tamiflu online (£50 per dose) from pimsreg.com registered with the Royal Pharmaceutical Society of Great Britain (RPSGB) and listed in "websites displaying the internet pharmacy logo".
Update 26 July 2009: Tamiflu - currently one dose is free to people exhibiting swine flu symptons - get Tamiflu from the UK Government Pandemic Flu site.
On 1 September my son went down with, what our doctor said 'ticked all the boxes' as swine flu. After 102F, vomiting, diarohea, headaches ... and taking tamiflu (our emergency stock) and on Thursday Relenza, he seems on the mend (4 September 8pm).
Diagram of influenza virus nomenclature (for a Fujian flu virus)
Structure of the influenza virion. The hemagglutinin (HA) and neuraminidase (NA) proteins are shown on the surface of the particle. The viral RNAs that make up the genome are shown as red coils inside the particle and bound to Ribonuclear Proteins (RNPs).