Novel H1N1: The pandemic evolves

The CDC has responded to pressures from the swine industry — and other sources, to be sure — to avoid the term “swine influenza” or even the more benign “swine origin influenza.” This was done to avoid further damage to the swine industry and also perhaps to alleviate concerns about transmission of influenza by ingesting pork or pork products. This concern has certainly been expressed at the public level, but also even at the governmental level! Several countries, apparently lacking understanding of the epidemiology of influenza, banned the importation of pork or pork products from the United States. Now we have “novel” H1N1 influenza viruses and this designation appears in all CDC publications. I will deal with the “pandemic” issue subsequently in these comments.

Note the chart, reproduced from CDC’s weekly summary of influenza surveillance data, “Fluview.” This is published weekly during the seasonal influenza season each year. Note the extraordinary double hump of positive tests for influenza reported since seasonal influenza started in late 2008. This is virtually without precedent since good surveillance data have been collected, especially this late in the influenza season. Of greater interest, note the composition of the second hump: it is not all due to novel H1N1 viruses. Rather, there has been an accompanying increase in seasonal influenza viruses as well. H3N2 viruses, in particular, accounted for a larger number of positive tests than was seen during the major seasonal wave.

Herald wave

The “herald wave,” a late season increase in an influenza virus type seen but little during the major part of the season has been described in the past, particularly by investigators in Houston, and is said to “presage” or predict the nature of the viruses that will be prevalent in the following season. This time, however, we may be dealing with two “herald waves,” one due to novel H1N1 virus and the other due to H3N2 virus. Could it be that we will see both viruses emerging next season? In view of the surprises we have seen this year, certainly it is possible.

As I write these comments, both seasonal influenza activity and novel H1N1 virus activity have declined sharply, with the exception of New York and New Jersey, which have been especially hard hit with swine-origin H1N1 viruses.

Some analogies could be made with what happened in 1957-1958. I am one of a diminishing number of people who remember those years vividly, since I was an intern at The Boston City Hospital that year.

In the spring of 1957, the H2N2 virus (Asian influenza) first appeared in the United States and gradually seeded the country, often causing small limited outbreaks during the summer months. One episode often quoted was the national Boy Scout Jamboree held in Iowa, with scouts from all over the country assembled; the jamboree was terminated by an outbreak of Asian influenza and the returning scouts, many now carrying the virus, spread it widely over the entire country.

Today, we are a much more mobile society than we were in 1957 and “seeding” of an entire country with, for example, novel H1N1 viruses takes only a few weeks instead of three to four months.

Worldwide outlook

At a global level, it is far too early to assess what is happening in the southern hemisphere, but there is clearly transmission going on in Australia and several countries in South America. More of that later in the summer.

According to WHO officials, a pandemic is underway. The WHO's definition simply requires sustained community transmission in more than one of WHO’s geographic regions.

A level 6 designation automatically results in a variety of emergency measures in member countries’ own pandemic preparedness plans, which likely would have been fully warranted in the case of avian influenza.

Accordingly, WHO is reconsidering this issue and likely will incorporate some measure of clinical severity into a new set of pandemic alert level definitions.

CDC response

Meanwhile, CDC continues to update its guidance in novel H1N1 influenza. These were very helpful early in the outbreak, but they are growing more and more complex and, in some cases, obfuscating.

A notable example is the use of facemasks and N95 respirators; in their zeal to cover every possible clinical situation, one has to spend quite a bit of time trying to find out their recommendations for a given set of circumstances. Furthermore, they are apparently still using the avian influenza model for their recommendations in recommending the use of N95 respirators in caring for patients with ILI, suspect, or proven H1N1 influenza. The New York City Department of Health has recently shown a ray of light by recommending a level of precautions identical to seasonal influenza. In particular, surgical masks are recommended for routine care rather than N95 respirators.

Prospects for vaccine

Finally, it appears all but certain that we shall have a swine-origin H1N1 influenza vaccine sometime in the fall. Seed strains developed at CDC are now in the hands of manufacturers and both Sanofi-Pasteur and GlaxoSmithKline have announced government contracts to produce a vaccine.

Unfortunately, we are still a year or two away from using a tissue culture-based production technology; hence, we must continue to rely on egg-based production. October and November seems a reasonable target date, with a possibility of some doses being available in September. More likely than not, it will be a two-dose series, perhaps with adjuvant added as an antigen-sparing measure. It is not at all clear how this vaccine will be integrated with seasonal vaccine administration.

I hope it will be possible to take an editorial “break” from influenza-related issues for a while, but I’m not at all optimistic!