The latest from Medscape:
Potential Impact of Swine Flu: An Expert Interview With Neal A. Halsey, MD
Laurie Barclay, MD
April 30, 2009 — Editor's note: The outbreak of swine influenza A (H1N1) viral disease is continuing to grow in the United States and globally, with 91 laboratory-confirmed US cases and 1 death, according to US Centers for Disease Control (CDC) information updated April 29 at 11 am EST. The World Health Organization (WHO) has issued a phase 5 pandemic alert, and the CDC has implemented its emergency response and warned that the more recent illnesses suggest a pattern of more severe disease associated with this virus in the United States. Because most people are not immune to this new viral strain, the CDC expects more confirmed cases, more hospitalizations, and more deaths in the near future.
To learn more about the potential impact of H1N1 viral disease on public health, as well as treatment and prevention strategies, Medscape Infectious Diseases interviewed Neal A. Halsey, MD, professor in the Department of International Health, Bloomberg School of Public Health, Johns Hopkins University in Baltimore, Maryland. Dr. Halsey's primary research and teaching effort is directed toward the prevention of infectious diseases with the safest vaccines possible. He has conducted or participated in epidemiologic studies of vaccine-preventable diseases and phase 1, 2, and 3 vaccine trials for influenza, hepatitis B, hepatitis A, inactivated polio virus, pertussis, Haemophilus influenzae type B, tetanus, Lyme disease, rotavirus, and Argentina hemorrhagic fever viruses
Medscape: How serious is the swine flu situation?
Dr. Halsey: The swine flu changes things and will change priorities for many people. The evidence that we have so far is that this does represent a potential threat to global public health, and a lot of resources are going to have to go into trying to prepare as best we can to minimize the impact.
That will include development, as rapidly as possible, of vaccines against this new strain and making those vaccines rapidly available. If we see more widespread transmission, especially this year, then drug therapy will be an important part, especially here in the developed world.
We need low-cost drugs against influenza in the developing countries as well, because we won't have enough vaccines to protect the population against this new virus. We don't have sufficient vaccine production capacity in the world to make enough vaccine for everybody.
The biggest concern I have is that this will distract us from use of other vaccines that also can protect against disease, like the new pneumococcal vaccine, and even the push to continue to introduce the Hib vaccine. But this new influenza is a serious threat.
Medscape: Are existing influenza vaccines effective against the new strain?
Dr. Halsey: No.
Medscape: How long would it take for a new vaccine to be developed and produced against this virus?
Dr. Halsey: That's what the manufacturers are going to be asked this week, and the answer, with the traditional method, is that we usually give manufacturers 4 to 6 months. They find out about the virus that's going to go in at the end of January, beginning of February, each year, and they make the vaccine, and make it available beginning as early as the end of September, beginning of October.
They've already been making the vaccine they thought was going to be in widespread use, and the key question is whether they should stop what they're doing and put the effort into producing vaccine against this new strain, and that will have to be answered.
There are some new technologies that are being used that may be more rapid in terms of making new vaccine, but they have not yet been widely used. All vaccines currently approved for use require eggs for production, and the supply of eggs is likely to be limited and the manufacturers do not have the capacity to produce enough vaccine for everyone, so there will be shortages.
A number of the manufacturers are experimenting with making cell-based vaccines that don't require eggs; that also could speed up the process, but so far, none of those vaccines that I know of has been approved for use. If we had the production capacity using these cell-based vaccines, it could be more rapid.
I'm sure that both the CDC and WHO are meeting with manufacturers of flu vaccines, and they're all looking at this, trying to determine what their capability will be, but we don't have any answers yet.
Medscape: Are antiviral drugs such as Tamiflu effective against this strain?
Dr. Halsey: Oseltamivir, or Tamiflu, and zanamivir (Relenza) are effective against this strain, but amantadine and the older drugs are not. They've tested the virus and it is susceptible to oseltamivir and zanamivir, which is the only good news out of what we've heard so far.
Medscape: Are there any concerns, with this new strain being a mixture of swine and avian and human strains, that this was in any way genetically engineered or terrorist-related?
Dr. Halsey: No, it doesn't look that way to me. We have been anticipating a potential pandemic from a virus that would come through that same kind of mixing. We know that especially pigs, or swine, are a great mixing bowl, because they are susceptible not only to the swine flu, but also influenza from birds and influenza from humans. So the same pig can have in its body simultaneously several different infections with several different viruses and allow for that mixing. This happens naturally, and that's part of why, especially in Asia, we've been seeing some problems with transmission. You don't need to invoke any concern about bioterrorism to explain how this may have happened.
Medscape: What do you see as the overall potential impact of this swine flu?
Dr. Halsey: The swine flu epidemic, or if it turns out to be a pandemic, which is what we're all concerned about, may turn out not only to have a significant effect on public health and potential mortality, but it could also potentially impair everything else we're trying to do with regard to immunization, in terms of using everybody available to deal with this problem.
It also could have a significant exacerbating effect on the global economy. They've already shut the schools in Mexico; they didn't have audiences for the soccer matches. You can imagine the impact it will have with regard to travel. Some individual countries in the European Union have issued some statements, or cautionary advisories, with regard to travel.
Imagine what the economic impact of loss of tourism in Mexico is going to be, and potentially the United States. So I see this as rapidly having an exacerbating effect on the current recession. This is not a small issue.
