Swine Flu: Worldwide Outlook

Inzune Hwang
Technical Specialty Unit, Centers for Disease Control and Prevention
Friday, May 1, 2009 12:30 PM

Inzune Hwang, lead in the Technical Security Unit of the Centers for Disease Control and Prevention, was online Friday, May 1, at 12:30 p.m. ET to discuss the latest information on the swine flu, including advice on travel, symptoms, when to seek medical attention and food consumption.


Washington, D.C.: I had a meeting this morning with a colleague from Mexico who came to D.C. on Monday. My colleague is not sick, but I was wondering how long the incubation period is and how much I should worry about the potential for infection. Is it possible for her to carry the flu if she is not exhibiting symptoms?

I have a 9-month baby at home and am most worried about her.

Inzune Hwang: Our current calculations on the incubation period, based on the case information that we have, is 1-5 days. It is possible to be infected and shedding virus without symptoms. Therefore, it is appropriate to use good hygiene precautions, such as handwashing, use of hand sanitizers, and covering your mouth when you cough or sneeze


Inzune Hwang: Good afternoon, everyone. This is Inzune Hwang, MD, MPH. I am the Preparedness Medical Officer for CDC's Influenza Division.


Washington, D.C.: We hear that officials from the World Health Organization today cautioned the public against jumping to any conclusions about the virulence -- the lethality -- of the swineflu virus. Can you explain this warning?

Inzune Hwang: The first country to be affected by this new influenza virus appears to be Mexico. They have reported a number of hospitalizations and deaths. Laboratory testing has confirmed that some of the patients who died had influenza H1N1 (2009)(swine-lineage). Although we have not yet detect many cases of severe illness and death in the United States and in other countries, it is too early to draw any conclusions


Atlanta, Ga.: Good afternoon -- we read a lot about new cases of H1N1 popping up -- 50 today, 100 tomorrow... but of the number that have contracted the virus, how many have perished? What's the percentage? If we've had 100 diagnosed in the U.S. since Sunday, and only 1 has died, doesn't that mean there's a 99 percent survival rate? We never get numbers like that... can you enlighten? Our media seems to be stirring a panic pot

Inzune Hwang: Great question. Of the 141 cases that we have confirmed diagnosis of Influenza H1N1 (2009)(Swine-lineage)to date, we have only 1 reported death. Although that is slightly less than 1%, we must consider that the entire population is currently susceptible to this virus.

In the 1918 pandemic, it was estimated that the case fatality ratio was 2%. That does not mean that this current outbreak will be half has severe. It means that we must continue to gather the best information that we can to determine the case fatality ration as accurately as possible.


Montgomery Co.: I am a high school teacher in a school that serves a large immigrant population, and I am 7 months pregnant. I sense that I'm at greater risk, but I'm not sure what actions to take to keep myself and my baby safe without completely over-reacting (other than washing hands, limiting close contact, etc.). Should I be considering taking time off and staying home during this time?

Also, my sister-in-law is traveling to Mexico next week and will be returning just in time to incubate some germs and then throw me a baby shower. Part of me wants to cancel, but is that over-reacting?

Inzune Hwang: Pregnant women are at higher risk for serious illness and complications than other persons. So, it is important to take appropriate precautions. CDC has posted guidance on www.cdc.gov regarding use of personal protective equipment, and, if circumstances warrant, use of antiviral medications.

Your decision to take time off is an important and personal one. You have to consider the financial implications, as well as the fact that it will be some time before an immunization is available for this strain. We should have better understanding of the risks of this virus as time goes on.

The risk of exposure to your sister-in-law is also a tricky one. We know Mexico is more severely affected, and have issued a travel warning against unnecessary travel there. We also know that there is a 1-5 day incubation period before someone infected may show any symptoms. You may consider postponing the shower 10-14 days after she returns if you are concerned. The goal of your shower is to pour happiness and love on you and your baby, not give you more concern.


Washington, D.C.: Should I cancel plans this weekend to see friends (with babies) if I have recently been in contact with people from Mexico?

Inzune Hwang: Our current, albeit, limited data on the incubation period for this new influenza virus is 1-5 days. General recommendations about how long to watch out for symptoms is at least 2 incubation periods. Therefore, if you are concerned, a general suggestion would be to consider avoiding non-essential social contact for 10-14 days.


Richmond, Va.: Are there any statistics on the number of people who got or didn't get the flu shot this year, and would it make a difference on the severtity?

Inzune Hwang: Over 130 million doses of seasonal influenza vaccine were produced for the 2008-2009 flu season. I believe approximately 25 million were not shipped. We cannot currently measure exactly how many doses were actually given to individuals.

We are currently in the process of determining how much cross protection seasonal influenza vaccine provides from this new H1N1 virus. Our preliminary data suggests little to no significant cross protection.


Vienna, Va.: If about 30,000 people die yearly from regular flu, then isn't this swine flu thing not a problem? Or contri-wise, why don't we have location maps and panic every winter with regular flu? I'm at a loss to understand the fuss.

Inzune Hwang: At CDC our goal is to minimize the spread and severity of any influenza. So, we work hard to prevent even one death from influenza. Our challenge in the present circumstance is to determine how this new influenza H1N1 strain behaves compared to other human influenza strains that circulate. The worst pandemic that we have on record, in 1918, killed many more than 30,000 and we want to be sure that does not occur again.

Actually, we do have maps on seasonal flu activity in every state, updated weekly on www.cdc.gov/flu. Look for FluView.


Redmond, Wash.: Good morning. Is it possible for this flu virus, in it's present form, to go from humans back to birds, or swine, and thus have more than one reservoir at a time, or must it mutate to again infect animals?

Inzune Hwang: Excellent questions. The short answer is yes! This current virus is a reassortant, meaning it has swine, avian, and human genes in it. It evolves that way because some animal was infected with multiple strains at once and produced a virus with a combination of genes (reassortment). At some point, the slow mutation of genes combined with this reassortment process produces a virus that can transmit easily in humans (our current situation). It is possible that it can transmit back to its source animal reservoir, or perhaps to another.

We have CDC veterinarians working with those from FAO and OIE (the animal equivalents of WHO) investigating the animal situation in Mexico to try to find an animal source.


Actual cases: What are the criteria for a doctor to report a positive case of this flu? If a patient comes in with respiratory symptoms, fever and aches, yes it's probably a flu. At this point are the doctors submitting blood for serotyping? Are they required to do this?

Inzune Hwang: Healthcare providers should contact their local public health authorities to report cases of influenza like illness that is suspicious for the new influenza H1N1 strain. They can provide the most up to date protocols for specimen collection.

Patients may always refuse any medical testing. Because of the increasing numbers of cases and the limited capacity to test, states may choose to change the recommendations for testing of persons with influena-like illness. Visit your local public health jurisdiction's website and www.cdc.gov to keep up on the changing guidance.


Washington, D.C.: The Post reported yesterday that a member of Energy Secretary Stephen Chu's security detail contracted the swine flu while on duty in Mexico, was sick for a few days with mild symptoms and then recovered. Three members of his family contracted the illness and had similarly short-lived and mild illnesse.

Why are we getting so worked up about a few days of mild illness?

Inzune Hwang: We are being very cautious because there are still a relatively few number of cases from which to draw good conclusions. In 1918, it is estimated that between 1 and 2% of American's died from the 1918 pandemic strain. While that seems a small number, when multiplied x 300 million people, it can be quite a serious problem. Remember also that our usual seasonal influenza strains are also still circulating.


Springfield, Va.: I read that the last several pandemic flu breakouts have followed a pattern of a weak spring breakout, after which everyone assumes it's run its course with little effect, and then a terrible breakout in the fall which is much, much worse. How does history such as this effect official response? If this current breakout seems to fizzle out, will anything be done to prepare for a worse breakout at a later time, or will officials just assume it's all over?

Inzune Hwang: Great observation. We generally expect that as the summer months come the rates of spread may decrease, then increase again during the fall and winter months. We are currently in the process of developing a vaccine for the new strain of influenza to try to produce a good supply in time for the coming influenza season.

CDC and the US Government will NOT consider this problem to be ended this year.


Jackson, Miss.: Just a comment that we have great confidence in you. Keep plugging. This is a tough row to hoe (as they say in Georgia) but CDC will lead the way.

Inzune Hwang: Thank you so much for your support. We have HUNDREDs of people working very hard right now on behalf of every American and citizen of the world.


Springfield, Va.: I do not understand all of the hype about the Swine Flu. How is this any different than any other flu outbreak? It sound as if, for the most part, if you get the swine flu you stay in bed for a week and you get better. Do they expect a far larger percentage of people who contract swine flu to die as opposed to the percentage of people who die from contracting any other type of flue?

Inzune Hwang: We only have a few weeks of data on this new influenza H1N1, therefore, we cannot say exactly how different this strain from other influenza strains in humans. That is why we are being cautious. We are committed to minimizing illness and loss of life. We are working feverishly with international, state, and local public health officials to measure what the rate of serious illness and death are and will let the public know as soon as we are confident in our data.


South Riding, Va.: Is it realistic to say that a vaccine will be available by the end of the year? I know there are flu vaccines, but for other conditions, it can take years to create an effective vaccine. Or as is the case for HIV, one has yet to be found.

Inzune Hwang: Because of the constantly changing nature of influenza, we develop new vaccines every year in the Northern Hemisphere and for the Southern Hemisphere. We have good practice and good partners in choosing and developing influenza vaccine. We are in close communication with vaccine manufacturers to ensure that a good supply of vaccine will be available for this fall.


Flu Deaths: I read in today's Post article that many of those who died in Mexico actually died of something OTHER THAN the flu -- the flu had weakened their immune system. Does this mean these people were already sick (chronic diseases) or that they got the flu and then got something else on top of it? I'm guessing also that "young and healthy" in Mexico is something vastly different than in the U.S. or Canada, in terms of nutrition, exposure to air pollution, etc.

Inzune Hwang: Great questions. We have CDC scientists working with WHO and Mexican scientists to help answer these questions in Mexico right now. Certainly, people with certain medical conditions are at higher risk for serious illness and death. The very young and the very old are also traditionally at higher risk. It is likely that some portion of individual may have been infected with more than one organism. The theory that this virus weakens the immune system for than other strains or causes an extraordinary response from the immune system has not been fully ruled in or ruled out. It is one of many questions that we are investigating, but cannot be answered with any certainty this early in the outbreak.


Bethesda, Md.: Do the instant hand sanitizers, the kind in a pump container, work to control the germs that could be passed for the swine flu? Is it possible to use too much of that? Thanks.

Inzune Hwang: Generally, YES, alcohol based hand sanitizers do a good job of killing influenza viruses. We have no reason to beieve that it should not kill the current virus. If it irritates your skin, that is too much.


Des Moines, Iowa: If those most at risk for severe symptoms are those with strong immune systems, such as those between the ages of 20-40, should people not take vitamins and attempt to eat healthy foods, etc.? Would they be better off not trying to boost their immunity in these ways in preparation for confronting the virus?

Inzune Hwang: Our current data shows that the very young are at increased risk. We are still unsure how severely it affects the elderly. The theory that healthy individuals between 20 and 40 are more severely affected is still being investigated. The theory that the immune system in healthy young adults is 'over-reacting' has also not yet been validated. This is a theory applied from some research on highly pathogenic avian influenza H5N1 in humans, but we cannot know if it applies to this new influenza H1N1.
Till then, healthy is always good.


Fairfax, Va.: What was the reason for changing the name of the flue to H1N1? Was there some religious reason?

Inzune Hwang: The term swine flu is used because the genetic analysis of the current virus is similar to those that we have studied in swine in the past. It is a historical designation. Currently, we have not identified a specific animal source. However, misconceptions that swine/pigs are the source or ongoing cause of the current outbreak have resulted in drastic reactions on the part of many populations. We want to do our part not to perpetuate any incorrect conclusions.


Washington, D.C.: Hi,

If you contracted the 1976 version of swine flu (as I did as a small child) might a person still have antibodies to this swine flu?

Thank you!

Inzune Hwang: It is possible, but our initial tests show that this virus is sufficiently different than the 1976 virus to tell us that there may not be much cross protection from the 1976 swine flu vaccine.


Rosario, Santa Fe Argentina: Hell, my name is Dr. Jorge Galindez, M.D. I´ll been exposed last Friday for 8 hours in the Benito Juarez Airport. Do you think it has been enough time, 7 days, so I can return to my job working in the field of HIV/AIDS. Thanks a lot.

Inzune Hwang: Our early data say that the incubation period is between 1-5 days. Our general recommendations are to wait 2 full incubation periods if there is a risk of infection. Considering realistic confidence intervals, it is reasonable to continue following current seasonal influenza guidance recommending 14 days of home isolation/quarantine.


Concord, Mass.: You indiate an estimated incubation period of 1-5 days. Do you have any estimate of the rate of onset of accute symptoms in severe cases?

Inzune Hwang: We currently have on record 9 confirmed cases of influenza H1N1 (2009)(swine-lineage) who have been hospitalized. That is an awfully small number from which to draw any conclusions, especially because some had underlying risk factors. There are some cases that had a rapid course from onset to hospitalization (<5-7days) and others that were longer. Sorry, I cannot be more definitive.


Menomonie, Wisc.:

In the past, we were told that SARS and the bird flu posed a great risk. But nothing came out of those diseases. Is it possible that the H1N1 virus could go the same way as those diseases? Is all the concern much ado about nothing?

Inzune Hwang: Unfortunately, avian influenza is STILL out there, as well as coronavirus (SARS). The risk level for each of these threats changes continuously. Therefore we must always be vigilant and prepared.


Rockville, Md.: Assuming that this strain of virus follows that of the 1918 Spanish flu (the first phase being relatively mild, the second having a high mortality rate), does that give us an advantage? I mean, unlike 1918, we have the ability to develop vaccines and include them into our annual fall flu shots.

Inzune Hwang: Our public health infrastructure gives us much better information than we had in 1918. Additionally, we have excellent vaccine development and manufacturing capability, effective antiviral medications, and personal protective equipment. We believe these give us a significant advantage compared to what we had in 1918.


Washington, D.C.: I am supposed to attend a family wedding next Saturday. Is it wise to go, in light of people attending who are flying to N.Y. from many different parts of the country? Additionally, we would have to stay in a hotel overnight. Is there cause for concern as to who proceeded us in the room and whether the hotel is being cleaned/disinfected properly? Could I end up contaminating my other family members by interacting with relatives who may have been exposed to the virus and/or staying in a strange hotel room that? My husband and I are in our sixties. Is attending the wedding amping up the odds of us getting sick from making such a trip? Or am I just being really paranoid? Thank you.

Inzune Hwang: Very hard questions. The answers to your questions are primarily based on your willingness/tolerance of risk. Certainly, with exposure comes risk. Since we are still early in this outbreak, there is no certainty if it will grow or start to decrease in N.Y. over the next week.

Personal protective equipment, hygiene precautions, and antiviral medications can help mitigate risk. Check our website at www.cdc.gov and speak to your healthcare provider to help analyze your personal risk factors and strategies to minimize risk.


"The situation continues to evolve rapidly. As of 06:00 GMT, 1 May 2009, 11 countries have officially reported 331 cases of influenza A(H1N1) infection," states the current news release from the World Health Organization.


Inzune Hwang: Thank you all for your questions. I will answer the current questions already entered.

Inzune Hwang, MD, MPH
CDC/Influenza Division _______________________

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