Media Briefing: Influenza A (H1N1)
(Conducted by Dr. Jon K. Andrus, Pan American Health Organization, June 4, 2009)
Good afternoon. Welcome again to members of the press corps on the line, and thank you for taking the time to listen to today's briefing by the Pan American Health Organization on the Influenza A (H1N1) epidemic.
- As of 4 June 2009, 66 countries have officially reported >19,000 cases of influenza A(H1N1) infection, including 125 deaths.
- Globally, WHO acknowledges that there appear to be 3 patterns of H1N1 viral spread:
- We have advanced spread in the US, Canada and Mexico with a mixed pattern where cases are increasing in some locations, declining in others, and increasing again in yet other areas after having decreased there.
- We have a transition in some countries in Europe, Asia, South America and Australia where there are larger numbers of cases and early spread into the community.
- There are limited cases in some other countries where the cases relate to travellers or communities.
- WHO calls this outbreak "moderate" rather than "mild" for three reasons:
- We know that the infection can be fatal both in those with underlying conditions and in perfectly healthy people too.
- We know that the overall number of serious and fatal cases is limited. However, we do not have a complete picture yet and do not know with any accuracy how many people are infected or seriously ill.
- But WHO has taken this to mean that we should expect outcomes to be similar to the pandemics of 1957 and 1968, when 1-4 million people may have died in each.
- There are other reasons why experts argue this is a moderate outbreak:
- The secondary attack rate in school children-that is, the percent of contacts of a known case who become infected-may be as high as 33%. This is higher than with seasonal influenza.
- The reproductive rate measuring the number of secondary cases produced from exposure to an infected case, ranges from 1.4 to 1.6, based on the Mexican data. Seasonal influenza has a reproductive rate a little bit less, at 1.3.
- In terms of clinical severity, in the US and Canada, 2 to 5% of infected people were hospitalized; in Mexico it was approximately 6%.
- Of all the deaths in the US and Canada, 2/3s occurred in people with chronic medical conditions. In Mexico, about 50% of deaths were in this category.
- We know that many developing countries just don't have the capacity to respond to the outbreak in the same way countries with more resources have been able to respond.
- Future impact remains to be seen, particularly over the next few months in the south. We will need to see how the virus evolves in the Southern Hemisphere over the next few weeks and then in the Northern Hemisphere in the fall.
- The best scientists and doctors in the world are working on this, but they cannot predict what is going to happen.
- Preliminary evidence suggests that the virus is displacing the seasonal virus in the southern cone countries.
- So, the bottom line is that we cannot be complacent. What may be happening in Chile is what happens with the usual evolution of a pandemic. The pandemic virus actually replaces the seasonal virus. We need to monitor this carefully because we also know that the virus is at risk for changing partly as a result of co-circulating with seasonal viruses.
- At this point in time, we remain at Phase 5 but are getting closer to Phase 6.
- Given the fact that we are getting closer to Phase 6, WHO held consultations 3 days ago, on June 1st, with over 30 experts from 23 countries, as well as experts from WHO country and regional offices to discuss the needs and concerns of countries and the steps WHO needs to take when considering when and if to go to Phase 6. Consensus was reached on the following:
- WHO will continue to use geographical spread for phase 6. There was overwhelming consensus from the experts to add an assessment of severity as well and to provide countries with guidance on how to construct severity scales that are relevant to individual countries' specific contexts.
- It is difficult to assess severity, but such an assessment must reflect the virulence of the virus, prevalence of risk factors related to the individual host, the vulnerability of populations, and countries' resilience or the capacity of health care systems to cope with a rapid increase in H1N1 patients.
- To that end, WHO will provide a global assessment and guidance, which is useful for the countries and can be adapted to local needs.
- Severity will vary over time and between and within countries, and this must be reflected in the assessment.
What WHO will do
As a result of this consultation and other discussions, WHO will finalize measures to assess severity and will provide simple, accessible guidelines to countries to help them prioritize and calibrate their actions. WHO will also help the public to better understand the meaning of Phase 6. WHO will coordinate such work with the International Health Regulations Emergency Committee.
Examples of actions that WHO would not recommend countries undertake, given the "moderate" nature of the epidemic, include:
- No trade restrictions on or culling of pigs
- No travel restrictions or border closures
PAHO looks forward to continue working very closely with key partners such as CDC of HHS of USA, and Public Health Canada to provide the best technical cooperation possible to our member countries.
Thank you. I will take any questions that you may have.