Freeman Spogli Institute for International Studies Program on Energy and Sustainable Development Stanford University

May 6, 2009 - CHP/PCOR News

Real time swine flu coverage: Stanford health experts regularly weigh in

By Teal Pennebaker

Stanford Health Policy experts use this forum to weigh in on the swine flu. Please note: the views expressed in each post are of the author and do not necessarily reflect the stance of Stanford Health Policy.

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Nayer Khazeni June 11, 2009 3:51PM PST: Over the past several weeks, WHO and international health experts have been closely examining whether the globally circulating novel A (H1N1) virus meets pandemic criteria. Today, WHO officially declared a pandemic. Director-General Margaret Chan gives a detailed explanation for the decision to raise the Pandemic Alert Phase to 6 ("Pandemic") at this time.

Daniella Perlroth May 6, 9:26AM PST: Consider that, so far, the swine flu of 2009 is providing a great "test run" of the global health care response to an actual deadly influenza pandemic (like a future H5N1?). Who can complain about a U.S.- acquired case fatality rate of .... 0.3% (2 confirmed deaths out of 642 cases as of this morning, and certainly there are a lot more unconfirmed cases out there). They made the right decision yesterday not to move forward with any more school closures. School closure alone isn't all that effective, but comes at substantial cost because parents have to forego work to stay at home with their kids.

Another thing we've learned from this: it appears unlikely that we are going to be able to stop influenza at its source (in this case Mexico) by slamming that area with millions of antiviral drugs, to prevent the virus from breaking out globally. This may sound amusing now, but that was the strategy ("ring prophylaxis") advocated by the WHO probably based on stochastic modeling. So maybe we can stop talking about this strategy (my google search of influenza and ring prophylaxis yielded 29,600 hits). And move on to those that would actually prevent influenza from spreading and people from dying (if it were actually severe, that is...).

May 6, 9:02AM PST: In a Time article, Douglas K. Owens weighs in on the effectiveness of Google's tracking of the epidemic.

Jay Bhattacharya May 5, 12:23PM PST: The CDC just announced that they will no longer be recommending that schools close because of the H1N1 flu. I think this means that we can declare this round with this virus over (though we should watch out for a resurgence in the late summer/fall which is what happened in 1918). Hand washing and other sensible precautions still make sense, but such precautions always make sense.

Jay Bhattacharya May 5, 9:10AM PST: Though this blog has been quiet, the swine flu keeps puttering along at a low level. In Santa Clara county, there have been a handful of confirmed H1N1 cases, but no deaths that I am aware of. County public health officials here have closed for varying periods of time at least seven schools that I know about. It will be interesting to see, ex post, whether the closing of the schools was worthwhile. I suppose the costs are low if the closure doesn't last too long--sort of like a snow day on the east coast--but the benefits may be low as well (at least in retrospect). Of course, that doesn't mean that the schools shouldn't have been closed, since officials in charge of making these decisions don't have the benefit of hindsight.

May 5, 7:51AM PST: In today's Mercury NewsDouglas K. Owens writes an op-ed about the vital role public health departments play in epidemics. But proposed budget cuts put these local resources in peril. Read Owens' op-ed "Who you gonna call? The role of public health departments."

Jay Bhattacharya May 2, 2:18PM PST: The latest reports I have seen seem to indicate that the H1N1 flu is not as virulent (at least in the cases seen in the US) as initially feared. Apparently though, the early infections during the 1918 flu epidemic were also not particularly virulent. At this point we don't know how this H1N1 virus will evolve, so it makes sense to keep taking sensible precautions.

These facts give us another reason not to overreact: it is possible that infection with the H1N1 virus currently circulating will provide resistance against a possibly more virulent later version.

May 2, 8:00AM PST: In a front page San Francisco Chronicle story, Douglas K. Owens comments on the aggressive response of public health officials to the swine flu, but notes his concern that "if this becomes widespread that our public health infrastructure is not going to be adequate to respond the way that we hope."

Kathryn McDonald, April 30, 5:04PM PST: I haven't seen very much in the press about one of the main reasons for a cautious approach - we do want this outbreak to settle down long before a single case arrives in a part of the world with high numbers of people with deficient immune systems and inadequate health care delivery systems. That's the horse that all the preparedness efforts are really trying to keep in the barn. Maybe we should be more worried about travelers from affected areas going to vulnerable places - low resource countries. They don't need any more infectious diseases than the ones that are already over-taxing their populations (e.g., HIV, tuberculosis, malaria, etc.).

Tamara Chapman, April 30, 5:54PM EST: Stanford Health Policy employee, reporting live from Washington, D.C. I spent all day Wednesday in a meeting at the Department of Health and Human Services (HHS) headquarters near Capitol Hill. Several meeting attendees are affiliated with our host organization, the Office of the Assistant Secretary for Preparedness and Response (ASPR). Here is what none of my ASPR colleagues were doing: panicking. Neither are the citizens and workers of D.C. panicking. The train is still packed, tourists are bustling, I have seen not a single mask, and, while of course in my meeting we informally discussed H1N1, we also managed to go about our normal non-flu business. When the government tells you to be cautious but not anxious, it seems to be practicing what it is preaching.

Before I make my way back to the west coast, I am taking a short trip to New York City. Admittedly, I used the fact that I have a health officer contact to inquire with an "insider" as to whether it is still a good idea to go through with the travel. According to him, I shouldn't be overly worried. I am still planning to make the trip in the morning. (I'll let you know if I see Joe Biden at the train station!) I am interested in seeing if and how the reaction and precautions taken by the public differ in New York from those in D.C.

Daniella Perlroth, April 30, 2:33PM PST: If you've recently returned from Mexico, enjoy time home. It's not that I don't want to see you, but it goes back to the reasons stated below related to asymptomatic shedding... you might be contagious before you get sick, so stay home for now! Especially if you went to one of these hot spots according to google. I'm not sure I could work as effectively if I kept going to the kitchen and bathroom here knowing that person-from-down-the-hall just got back with that amazing tan from Mexico...

Jay Bhattacharya, April 30, 10:01AM PST: I understand the reasoning behind inducing a needless panic--the panic, by inducing self-protective behavior makes itself needless. However, the costs of this ironic cry wolf strategy are substantial. First, consider the direct economic costs of panic: if everyone followed Vice President Biden's foolish advice to avoid planes, trains, and other confined spaces, this would more or less shut down the economy overnight. Second, the sort of self-protective activities people engage in during a panic are often very damaging in and of themselves, even if they cost nothing. It makes no sense to avoid contact with all Mexican-Americans in the U.S. just because the epidemic may have started in Mexico, yet this is a likely outcome of the sort of panic that I am seeing. Third, there's a real cost to the authority of public health officials (and political officials) from crying wolf. I no longer trust the folks who warned about a year 2000 computer bug catastrophe, even though their incitement to panic may have rendered the problem moot. Can we really afford to have the public not trust public health officials? What happens during the next epidemic?

The right strategy is to put out responsible advice that relies on well-established science and is honest about what we don't know.

Daniella Perlroth, April 30, 8:55AM PST: Asymptomatic viral shedding. If you are going to protect yourself, you need to understand this. It means that people shed the virus causing flu, and therefore can give it to you, when they feel entirely well. It happens for a few days before people actually get sick. They feel well, so even though the virus is being shed in high numbers from their nose, they proceed with their day as usual: using that atm machine just before you get there, standing behind you in the grocery line and then sneezing on you, shaking hands at your kid's school play, you get the picture.

By the time we recognize a case of flu, that person has shed for a day or more and made contact with maybe 2-10 unaware individuals who are now incubating the virus. If you understand this concept, when government asks you to "distance yourself socially," you just might be more likely to follow their instructions.

Keith Humphreys, April 30, 6:35AM PST: Please panic - it helps me relax.  Although we usually describe infectious disease warnings in virtuous terms ("educating the public"), what we are really doing is inducing fear that we hope will motivate behavior change. In principle, not getting an infectious illness in the future ought to drive preventive behavior now, but we never know if our preventive efforts actually paid off. The fellow who washed his hands 20 times a day may have been at no risk for swine flu in the first place, and was therefore wasting his time and rubbing his skin raw for nothing. What actually rewards preventive behavior more proximately is a reduced sense of anxiety: There, I've gone and bought a mask, I have just made myself safer and I feel more relaxed now. Health warnings drive up everyone's anxiety, making this sense of relief from preventive behavior more palpable and influential.

The irony is that engaging in preventive behavior is not the only way to become less anxious about getting swine flu or any other infectious disease. Because of "herd immunity" our efforts to prevent infectious disease radiate to those around us. The first year the Rotateq vaccine came out, a pediatrician advised me about whether I should have my twin sons vaccinated: "It works, but it's brand new, it may have side effects we don't know about yet." I asked her if other patients were getting the vaccine and she said "Yes, people are mad for it, it seems like all I am doing these days." So I didn't vaccinate my children. I knew that if everyone else was anxious enough to get the vaccine, my family would get lower disease risk "for free." To put it another way, I felt relaxed because everyone else was scared. And that season was the most mild for rotavirus in many years, with the reduction in infections being far greater than what the number of vaccinations explained directly. The rest of the reduction was experienced by parasites like me (Thanks everyone!).

Behavior that could prevent infectious disease thus involves a psychological gamble. Your anxiety about getting swine flu depends on the behavior of the people around you. To the extent that they panic and engage in intensive preventive efforts, their anxiety goes down. But so does yours even if you personally do nothing. If everyone you encounter is already washing their hands every 15 seconds and wearing a mask, your anxiety drops dramatically with no effort on your part. You can thus relax because everyone else in panicking.

Jay Bhattacharya, April 29, 9:18PM PST: A health economist friend of mine passed along the following link which shows the progress of the epidemic to date:

The link also tracks media mentions about the epidemic. At this point, it seems to me that the panic about the flu outstrips the actual harm it has caused, though that could change in the future.

For the record, the link that Dr. Perlroth posted gives the right advice on the topic: stockpiling Tamiflu is unnecessary at this point from a personal point of view, and harmful from a public health point of view.

Daniella Perlroth, April 29, 5:14PM PST: I've heard rumors of people ordering Tamiflu from an internet pharmacy in Canada yesterday.  Hmm.  This seems like a good cop-out suggestion for me to pass along to those long lost friends and relatives who want me to prescribe them a tamiflu stockpile, even though they haven't taken a Mexico jaunt in years and never leave their computer spreadsheets during daylight hours (not that I would know anyone like that).  Here's what the NEJM has to say on physicians like me prescribing Tamiflu.  Bottom line is don't do it now, as it takes away from the public good at this point in the near-pandemic.  Of course, that probably doesn't make would-be tamiflu stockpilers rest easier.  I'll let someone else opine on the relative risk of dying from swine flu versus getting hit by a car while biking home from the office tonight.  Especially when you haven't slept for days and forgot your helmet (as in my case).

Jay Bhattacharya, April 29, 5:02PM PST: I agree with my colleagues that this has the potential to be a major outbreak.  Still, there is no reason to panic.  Instead, common sense precautions will go a long way in limiting the spread of this H1N1 virus.  For instance, wash your hands more frequently than usual.  This is especially important for people who work in professions that require lots of interactions with the public.  Also, if you come down with flu-like symptoms, stay home from work until you feel better!  Most likely, you have a common cold, but there's no reason to risk getting your co-workers sick.

Douglas K. Owens, April 29, 4:50PM PST: Two factors are important in determining the impact of a flu pandemic on the population.  The first is the mortality rate in those who are infected. The second factor is how easily the virus is transmitted from person to person.  In studies that model the impact of flu, the ease of transmission is captured by a parameter known as the reproductive number.  The reproductive number represents the number of new infections that occur from each infected person in a completely susceptible population.  A reproductive number of two indicates that each person with flu will infect two more people on average, if all the person's contacts are susceptible.  In the 1918 flu epidemic, one of the worst on record, the mortality rate among people who were infected was about 2%, and the reproductive number was 1.8 to 2.0.

Both the mortality rate and ease of transmission are still uncertain for the 2009 swine flu.  Although the mortality in Mexico appears high, the true number of cases of flu is unknown, so it is not possible to determine the proportion of people who have died.  The mortality rate in the U.S appears to be low so far, but may evolve as the epidemic spreads.  The reproductive number is also not known.  However, the apparent high attack rate in some groups (such as the students in New York) and the fact that infection is occurring in many places are both of concern.  As more information becomes available to estimate the mortality and ease of transmission, the likely impact of the swine flu on the population will become clearer. 

Jay Bhattacharya, April 29, 4:34PM PST: There's a lot of misinformation out there about the how the swine flu is spread.  For instance, despite what you may have heard, it not true that you can catch the flu from eating pork or chicken or any other cooked food.  You catch it from being in close proximity to someone else with the flu.

Eran Bendavid, April 29, 3:27PM PST: Influenza is often classified according to the hemagglutinin (H) and neuraminidase (N) proteins.  The current swine flu is subtype H1N1, which is the same subtype responsible for the 1918 pandmemic flu.  Swine flu H1N1 cases have been reported in humans over the past several years, but the key step – transmission from one human to another – was absent until this episode.  The influenza virus has a remarkable ability to shuffle and reorganize its genetic code, and it seems this episode resulted from such a reassortment.  Because this strain has never caused a significant outbreak before, the entire population is susceptible, and it will take several months to develop an effective vaccine.  It has the makings of a major outbreak.

Nayer Khazeni, April 29, 3:07PM PST: The World Health Organization (WHO) raised the Pandemic Alert Phase from 3 (sporadic human disease without sustained human-to-human transmission) to 4 (sustained human-to-human transmission) on Monday and from 4 to 5 (human-to-human spread of the virus into at least two countries in one WHO region) a few hours ago. We were at Phase 3 for influenza A H5N1 of avian origin for several years, with the assumption that if the level were raised to 4, moving from phases 4 to 6 (pandemic phase) could be rapid—this is what we’re seeing now for influenza A H1N1 of swine origin. Here is WHO Director-General Margaret Chan’s statement on the evolving situation, and the WHO’s decision to increase the alert level.

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