Swine Flu: Cases Confirmed in Israel and New Zealand

Ruth Karron
Professor and Director, Center for Immunization Research and Vaccine Initiative, Johns Hopkins Bloomberg School of Public Health
Tuesday, April 28, 2009; 2:00 PM

Ruth Karron, professor and director of the Center for Immunization Research and Vaccine Initiative at Johns Hopkins Bloomberg School of Public Health, was online Tuesday, April 28, at 2 p.m. ET discuss the latest news about the swine flu, which has now spread to the Middle East and the Asia-Pacific regions as the World Health Organization raises its threat level from 3 to 4, two levels below a full-scale pandemic.


Ruth Karron: Hi, this is Ruth Karron from Johns Hopkins Bloomberg School of Public Health, here to answer your questions about swine flu.


Seattle, Wash.: It is suggested that we use Social Distancing to reduce our chance of exposure to the flu. Please define Social Distancing. When should we implement this and for how long? Thank you.

Ruth Karron: Social distancing is an effort to slow the spread of an infectious disease by decreasing opportunities for people to congregate--for example, closing schools, or places or work or worship. In extreme instances, individuals might be asked to 'shelter in place'--to stay at home for a period of time.

Social distancing should be implemented at the advice of local government and public health professionals, who will take into account the rate of spread and severity of disease.


Great Falls, Va.: Should we all get immunized specifically for swine flu?

If so, what might be the side effects? Thanks.

Ruth Karron: Right now there is no vaccine for swine flu. Although the swine flu virus is an H1N1 influenza A strain and we have H1N1 influenza in our seasonal flu vaccine, these are very different viruses. We wouldn't expect any protection from the regular (seasonal) flu vaccine.


Spokane, Wash.: How does the CDC reliably track swine flu if a person's doctor doesn't want to see the patient? At what point does one become sick enough to insist one being examined How does a doctor decide to take swabs for culture? I became very sick in Feb. 2005 with a flu going around at the time (I suspect it was A/California) and had all the symptoms -- sudden onset, non-stop cough, fever over 102, body aches -- but my doctor would not see me; just told me to stay home and take the usual steps to relieve symptoms.

Ruth Karron: I think that these are different circumstances than would apply during a regular flu season. At this time, health care providers are being specifically asked to see patients with fever and flu-like symptoms not only to care for the patient, but also to provide important epidemiologic information about this new flu virus. If, under these circumstances, your health care provider was unable to see you, I'd recommend contacting your local health department for advice as to where to be evaluated.


D.C.: Can pets (ie: dogs, cats, other) catch and/or transmit swine flu? Is there likely to be massive killings of pigs (as birds were slaughtered previously for avian flu)?

Ruth Karron: There is no evidence at this time that domestic animals can be infected with or transmit swine flu. It is also unlikely that pigs will be slaughtered, as previously happened with birds in Hong Kong. That culling was done for containment: to prevent spread of H5N1 beyond a localized area. But with swine flu, we are already beyond the point of containment.


Columbus, Ohio: My fiance and I have booked our honeymoon to Mexico in late June. Do we need to reconsider our travel plans? And just how dangerous is swine flu really? Thanks!

Ruth Karron: Unfortunately, it is too early to predict what the state of affairs will be in June. At this point, we know that the cases that have come to medical attention in Mexico have been more severe than cases in the US or other parts of the world, but we don't yet know why that is.


Alexandria, Va.: Last week I was out of the office for 4 days with flu symptoms. I thought it peculiar that I had a flu in April. I have colleagues who are out of the office this week with the flu, too. Is there another strain going around right now that could be confused with this worrisome H1N1 swine flu?

Ruth Karron: It's important to clarify what we mean by "flu symptoms", since many people will call cold symptoms (runny nose, cough, etc) or GI symptoms (nausea or vomiting) the flu. Real flu gives you a fever (and fevers are pretty uncommon in adults), sore throat, cough, muscle aches, and occasionally GI symptoms. These symptoms often come on very suddenly. Runny nose is actually much less common with flu.

That having been said, we actually did have a late flu season this year, with flu B (a regular, seasonal strain) extending into April. But I think that the regular flu season is coming to a close, so we should be suspicious of swine flu for anyone with a fever and other symptoms, as described above.


Anonymous: What is the tipping point to determine that this a pandemic virus? Is it based on how many people have the flu or how many die or how far spread and who makes that determination ?

Ruth Karron: An influenza outbreak is defined as pandemic when there is sustained global transmission (human-to-human spread) of a new influenza virus to which the world's population is not immune. Severity itself does not play into the definition of a pandemic: there can be severe pandemics (1918) or milder pandemics (many of the other pandemics of the 20th century).

The determination is made by WHO.


Anonymous: Is an immunity for this type of flu possible ?

Ruth Karron: At this time, we presume that people have no immunity to this new virus--that is why it is able to spread so rapidly. It is likely that vaccines could be produced that would provide immunity to this virus.


Herndon, Va.: I just don't understand what the big deal is about this flu (or the bird flu or SARS). Why are these health organizations getting everyone in such a panic? Do we really need to worry about this at all?

Ruth Karron: The reason that everyone is so worried about this flu is that it is a brand new virus that can be spread from person to person, and has already been detected in many places in the world. This swine flu virus is very different from the H5N1 'bird flu' virus in 2 important ways: 1) it is much less fatal (H5N1 killed about 50% of the people that it infected) 2) it spreads much more easily from person to person.

This situation does need to be monitored closely, with the types of surveillance that are already in place.


Virginia Beach, Va.: Since there is no effective vaccine for swine flu, can you suggest medications that would be most effective in treating it?

Ruth Karron: Currently the two neuraminidase inhibitors: oseltamivir (tamiflu) and zanamivir (Relenza) appear to be effective against the swine flu.


Hyattsville, Md.: Do you feel that there is any significance in the fact this swine flu seem to be affecting the younger age group so significantly?

Ruth Karron: More information about this should be available in the days and weeks to come. At this point, we are still getting information about the epidemiology of this disease in Mexico, and it is possible (likely, in fact) that there have been many mild cases that have been undetected.

As far as the US cases are concerned, there are probably too few to make any firm conclusions about age groups. Since most cases had some connection to travel in Mexico, it's also important to consider whether that might play a role (whether the groups of people travelling to Mexico in April are likely to have been younger than the general US population).


San Francisco, Calif.: Possibly a dumb question, but is pork to be avoided? (I haven't heard anyone talk about that yet.)

Ruth Karron: No, no need to avoid pork.


South Bend, Ind.: For how long can someone with swine flu be contagious before developing symptoms?

Ruth Karron: A person can be contagious for 1-2 days before they develop flu symptoms.


What not do to: I've heard about people showing up at ERs to check if they have the flu, even those who aren't really sick. This will overtax our health care workers and delay treatment for people who are at the ER because they really are sick or injured.

Isn't the best thing to do right now to wash our hands and cover our mouths when we cough (coughing into our elbows if possible.

Ruth Karron: I completely agree with you about ER visits. I would, though, urge people to contact a health care provider or local health department if they have a fever (not other mild symptoms)--please see my earlier comment about definitions of the flu.


Rockville, Md.: What would it take to create a vaccine for this swine flu? Why do annual flu vaccines typically only contain two or three strains?

Ruth Karron: The CDC has announced that it has already made the seed virus for a vaccine--this is what the manufacturers would need to use as a starting point. A decision (by the CDC and WHO) would need to be made that we should make a swine flu vaccine this year--that decision will probable be made in the coming weeks based on what we see happening in the world. Manufacturers are already making the annual vaccines, so they would probably need to set those aside to work on swine flu vaccines.

The annual flu vaccine only contains 2 or 3 strains because it has to be manufactured each year, and there is a limit to that manufacturing capacity.


Alexandria, Va.: Thanks so much for doing this chat.

You said that most of the cases here in the U.S. occurred in people who had traveled to Mexico. What about in other countries? Does there seem to be a clear line of causality here, or has the virus become widespread enough that even those who have not traveled to Mexico (or don't know anyone who has) need to be concerned?

Ruth Karron: To my knowledge, most cases in other countries have had some link to Mexico (either personal travel or close contact with a traveller).


Pennsylvania Farmer: Pork Industry up in arms about calling this swine flu. Is it correct that it has nothing to do with swine and if so why the name ?

Ruth Karron: Viruses from human cases have been sequenced and they appear to share sequences with viruses isolated from swine--hence the name. As I noted previously, people should not be concerned about eating pork.


Cabin John, Md.: In the 1918 Spanish Flu pandemic, there was an initial, milder sweep of the flu in May, and then a more virulent reprise of it in October. Could that happen with the swine flu?

Ruth Karron: That is possible, but really cannot be predicted. If this outbreak continues, we would hope to have vaccines available as well as antivirals in that event.


College Park, Md.: Is it possible that people exposed to the 1918 Swine Flu could have partial immunity from the modern strain, which also has avian and human flu DNA?

Ruth Karron: The genetic information about this swine flu is still evolving-- so I don't think it's possible to link to 1918. In any event, we would be talking about a very small population of the extreme elderly!


Washington, D.C.: It appears that a 4-year-old boy that contracted swine flu in Veracruz is considered "patient zero." Why is it so important to identify this first point of transfer from animal to human?

Ruth Karron: It gives us some clue about possible mechanisms of animal to human transmission and spread through a community. In terms of mitigation (slowing spread or decreasing illness) , it doesn't matter quite as much.


Washington, D.C.: How long does it take to get over the Swine flu and how many days are you considered contagious?

Ruth Karron: The current CDC recommendation is that people remain at home for at least 7 days or for 2 days after their symptoms have stopped, whichever is longer.


Philadelphia, Pa.: When I see the threat level has been raised to 4, I wonder: what causes a threat level to reach 5?

Ruth Karron: The threat level would reach 5 if there was evidence of sustained, large group transmission in multiple locations.


Ruth Karron: Thanks for all of your excellent questions. I'll be signing off now. Ruth Karron


In an interview with washingtonpost.com, Karron says, "The swine flu outbreak is evolving rapidly -- as Dr. Keiji Fukuda at WHO says, 'this is not yet a pandemic but it is a fluid situation.' There are confirmed cases in Mexico, the U.S., Spain, the U.K., Israel and New Zealand. As surveillance continues, new cases will undoubtedly be identified."


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