BCM flu experts answer H1N1 flu (swine flu) questions

Dipali Pathak
713-798-4710
pathak@bcm.edu

HOUSTON -- (April 27, 2009) -- Experts in BCM's Influenza Research Center answer questions about H1N1 flu (swine flu).

Swine flu Q & A with Dr. W. Paul Glezen

Why are we concerned about this particular outbreak of influenza?

It appears to be a novel virus – in other words a virus that humans haven't had experience with. That raises the specter of pandemic so we have to pay attention to it.

How is this swine flu outbreak different from the concern we had about swine flu in 1976?

The 1976 virus was completely a swine virus but it mutated in a way that allowed it to spread from person to person. It did not have the same gene makeup as this virus. The current swine virus has gene segments from the Eurasian swine, the north American swine, avian and human viruses. It is in some way or another re-assorted with four different viruses to produce this virus. It is a novel construction and we don't know yet how virulent it will be or how much it will spread, but it is definitely a different virus.

What is the situation in the United States right now?

It looks like the virus is seeded in several areas. There are three or four scenarios that could happen. We could have seeding now with small outbreaks that would tend to die out with warm weather and kids dispersing from school. Or we could have a hiatus in the summer without much spread, but then we would have to expect that it would come back early next fall, when the temperature goes down, humidity goes down and kids go back to school.

What is the situation in Mexico now, as you understand it?

This virus is spreading throughout the country, particularly in Mexico City, which is one of the largest urban areas in the world. There are 20 million people there and they are living under relatively crowded conditions. This unfortunately is an ideal situation for spread of a respiratory virus like influenza. There has obviously been a lot of spread there and there have been serious illnesses, and most of these have been in young adults so far. As far as outlying areas, we know that in cities like San Luis Potosi there have been a lot of infections. It has spread throughout the country and is producing a lot of illness.

Does a pandemic have to be deadly?

A pandemic is certainly going to be deadly. We see mortality every year with even seasonal flu. A pandemic by definition means that everybody is susceptible to the virus so it means there will be mortality.

Why is the official reaction in Mexico so different from that in the United States?

Obviously the virus started spreading there much earlier than here in the United States. We can't say exactly when it started spreading but it has probably been over a month and it has spread very rapidly. We can hope that it won't happen here but we can't rule out the possibility either. It could continue to build here in this country in the spring and in hot weather but we hope that it won't.

What can people do today to avoid catching this flu?

You can avoid crowds and avoid people who are coughing and sneezing as much as possible. If you think that you have had contact with somebody who might be infectious, you can take one of the neuraminidase inhibitors. The dose is prescribed for prevention of infection so people who are likely exposed can take advantage of those drugs to prevent infection. That is about all you can do until we get a vaccine.

Does the vaccine protect us from the flu?

Vaccines work pretty well if we have a good match between the antigens which are in the vaccine and the virus which is spreading. If a vaccine was made for this virus I would expect it to be effective. Now, there are some qualifications we have to make – we know that the very young and the very old don't respond as well to flu vaccines as people in the middle. School-age children through adulthood generally respond to the vaccines better and get better protection, at least with the vaccines we have now.

The CDC says, and I'm quoting a very recent announcement, that, "You can't expect protection with the current vaccine." However, that doesn't rule out that there might be some cross protection. I haven't yet seen the studies which would rule out this possibility. Even if there is just some protection, it may reduce mortality.

Why are most of the people getting this flu under the age of 40?

Historically, when a pandemic starts the people first affected are those who have the most contact in the community. Working adults and school children are usually at the forefront of any epidemic, and certainly pandemics. When you have a pandemic strain to which everybody is susceptible then you are going to see deaths in school kids and young adults first because they're the first ones that are hit.

What should we do if we have a fever and/or sniffles and cough?

At this stage, if you have a fever and cough and sore throat, it is important to go to a clinic where you can be cultured and get a specimen that can be tested for the influenza A virus. If it were Influenza A virus you would have to suspect that it might be the swine virus. In that case, a specimen would also need to be sent to the public health lab so that swine flu could be definitely identified.

Which medicines work against this strain of influenza?

The neuraminidase inhibitors work against it. This includes tamivir (trade name Tamiflu) and zanamavir (trade name Relenza). Tamiflu is given by tablets to adults and older children, and there is syrup for children down to age 1. Relenza is given by inhalation and therefore it requires active participation of the patient so it can't be given to young children under age 7. Debilitated people also do not manage it well. In addition, we generally do not give it to people with asthma because the inhalation of Relenza is often irritating to them.

We had an outbreak of H1N1 flu this year. How is this different?

The human virus of course has all the gene segments that are human. This virus is very different because it is swine virus. Now, when they sequence this new swine virus they can see a lot of different amino acids and they say it is different. What we need to see though are antibody tests. This would involve taking serum from people who got this year's vaccine and testing it against the new epidemic virus and vice versa. We need to see if antibodies generated by the swine virus will protect against the current H1N1. There is also previous experience. For example, are people who got the 1976 swine vaccine protected? Or maybe people a certain age? We have seen this in previous epidemics that people, say over 75, are protected against the new pandemic virus because the same virus had circulated 60 or 70 years before. There are all these possibilities that some segments of the population may have antibodies to this or may have some partial immunity. We need to have more information. Right now they say the current vaccine doesn't protect and we can't depend on protection from infection from this year's H1N1.

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