Influenza virus H1N1 Mexico 2009

As all of us, you probably have been following with the utmost attention the recent events on human cases of influenza A/H1N1 virus in Mexico and elsewhere.

To avoid panic and make the right decisions, here are some information to keep in mind and disseminate within your technical services.

The current Epidemic

The influenza virus involved has elements of human, pigs and avian influenza viruses. Moreover, it appears that no human victim of this flu was in direct or indirect contact with pigs. Finally, to date, no swine mortality due to this virus strain was observed. We invite you to use the term "swine influenza", used by the media, with the greatest caution, or better, to avoid it.
We must therefore keep a cool head and avoid panic amongst farmers and consumers that could be catastrophic for the pig industry of your respective countries.
The situation is exactly opposite to what we experienced with the highly pathogenic avian influenza:

 The avian flu is a disease affecting susceptible birds and that can exceptionally be transmitted to humans in case of close and prolonged contact (zoonosis). The pandemic risk from H5N1 is possible but not predictable or quantifiable.
In this case, the issue is was to protect humans against a possible contamination by virus or a mutated virus from an animal.

In contrast:
 The influenza A/H1N1 virus strain circulating in Mexico and elsewhere, is a human virus whose pathogenicity for other species (pigs, poultry etc.) is to date unknown.
Efforts should be therefore made to protect pigs (or avian) against possible contamination of human origin.

Actions to be considered:

We propose to settle two levels of alert:

 Level 1 (current): Inform farmers about what swine influenza is and what the current epidemic is. (see attached OIE monograph and FAO brief);
Encourage farmers to strengthen biosecurity measures (in particular prohibit farms’ access to outsiders and avoid pigs straying).

If psychosis effects can already be felt, it would be urgent to communicate on this topic keeping in mind the above information.

 Level 2: Enhanced surveillance with reporting of suspected cases and shipment of ad-hoc samples (nasal swabs) to reference laboratories. [1]

Rapid influenza A antigen detection:
The tests that you are using for highly pathogenic avian influenza H5N1 are perfectly usable for a first field diagnostic, in order to confirm a suspicion of swine influenza A.

Level 2 will be particularly appropriate if cases of human influenza A/H1N1 were reported in your country.

Conclusion

We must mobilize our public health colleagues who are primarily concerned in implementing preventive measures and awareness in the main risky entry points such as sea port and airports for people travelling to or from affected countries.

OIE Swine influenza