Sharon Stranford on H1N1

Monday, December 7, 2009 - 12:00

According to estimates recently released by the Centers for Disease Control (CDC), between April and mid-October of this year some 22 million Americans contracted the H1N1 virus, i.e., swine flu. The virus has contributed to or caused nearly 4,000 deaths, including those of 540 children. The CDC report also estimates cases of H1N1 have resulted in about 98,000 hospitalizations in this country, including 36,000 for children. To date there have been 120 suspected cases of H1N1 among Mount Holyoke students, although no student has required hospitalization.

Questioning Authority asked associate professor of biological sciences Sharon Stranford, an immunology expert, to evaluate the seriousness of this pandemic.

Q: We've been hearing about H1N1 since last spring, and many people think the situation has been sensationalized by the media. Is H1N1 serious enough to warrant all the attention it has received?

SS: Any pandemic that can result in the kind of morbidity and mortality rates that this virus seems to exhibit is cause for concern, especially in the very young, the elderly, and in immunocompromised individuals. Initial estimates of mortality rates in Mexico may have been artificially high, as most of the numbers came from studying only the most serious cases seen in those seeking medical assistance. It is still true that the number of individuals being hospitalized or admitted to the ICU is quite high for this virus strain. Of those entering the ICU for flu, death rates are much higher this year than in the recent past.

Q: What's different about the H1N1 virus that sets it apart from the usual seasonal flu?

SS: In some cases, infection with H1N1 appears to generate more severe symptoms with a slightly longer duration then in past years, and with higher rates of mortality, especially in individuals with other risk factors (e.g., respiratory problems). The main difference is in the genetic make-up of the virus, which acquired whole new stretches of DNA that differ from last year’s predominant strain. This differs from the small DNA changes that are typical from year to year for influenza virus. Therefore, our immune systems are unlikely to have previously encountered a strain of influenza that looks much like this one. This leaves most of us more vulnerable to infection.

Q: Is it more contagious than other viruses?

SS: The H1N1 does not seem to be significantly more contagious, or infectious, than a typical influenza virus. However, as a population we are more vulnerable to infection because we have little if any immunologic memory of a virus that looks like this, and this one looks very different from last year’s strain.

Q: Have we ever had an H1N1 epidemic before this year?

SS: Not this particular version. The “H” and “N” refer to two different structures on the surface of the virus. The DNA sequences for the 2009 H1 and N1 versions of these protein structures are very different from last year’s H and N, or from these sequences from flu viruses encountered in the recent past.

Q: We've always heard older people are particularly vulnerable when seasonal flu comes around each year, but with H1N1 people over 65 are said to be at the least risk. Why is this?

SS: You asked about whether we’ve ever had an H1N1 epidemic before and, although the answer is probably not, there have been years (more than 60 years ago) when the population was believed to have been exposed to a flu strain that may have looked a bit more like the current H1N1 than in the intervening years. This means that some people over 65 who encountered that virus when they were young are relatively immune, or protected, from infection with this virus. The immune system can sometimes have a very long memory!

Q: Are there more deaths from the H1N1 virus than we usually see with seasonal flu? Is it a more dangerous strain--or are there just more people getting the flu than usual?

SS: Initially mortality rates from Mexico were quite high, but this may have been due to the fact that most of the reported cases came from those seeking medical help. If many others were infected but did not report their “mild” infections, death rates can appear artificially high. Having said this, some of the initial observations made in Mexico still hold true in the United States. For example, once someone is hospitalized for flu, and especially when individuals are admitted to the ICU, the risk of death due to flu is significantly higher this year than in most years.

Q: Should we get the H1N1 vaccine? Is it safe?

SS: I’ll start with safety. I believe that this vaccine is likely to be as safe as our typical seasonal flu vaccines are each year. It's a myth that this vaccine was prepared too hastily. In fact, although this vaccine was prepared on a slightly more rapid schedule and with many more doses, the same procedures and rough time line were followed (with the exception of the specific virus used in the preparation). The effectiveness of the H1N1 vaccine remains to be seen. Those data we will only really have when flu season is finally over.

As for whether to get the vaccine, that is a very personal choice. I can say that the fewer people who get the vaccine the more infections we will see, which means more spread to others. Those others may not be as robust in their ability to fight the virus--for example, the very young, pregnant women, the elderly, or immune-compromised individuals. In addition to personal health, I also think these factors are important to consider as we make vaccination decisions.

With that said, I’m off to wait in line for my vaccine! Wash your hands, often!

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