infectious disease
revere | May 30, 2009The natural reservoir for most influenza viruses is birds, especially aquatic birds, but some versions of the virus have also become adapted to the host cells of other species, among them sea mammals, horses, dogs and of course pigs and humans (among others). How long is the list? We really don't know, as there has been little systematic inquiry into influenza hosts in the natural world. While human influenza is seasonal in the northern and southern hemispheres, where it goes in the "off season" is a matter of debate. Most flu experts think it remains at low levels in the community, spiking…
revere | May 27, 2009Yesterday New York reported two more swine flu deaths (a 41-year-old woman from Queens and a 34-year-old man from Brooklyn). CDC and just about everyone else who knows anything about influenza have been telling people to expect this. The influenza virus kills people all the time. We don't know exactly how many but we know that many people die of various immediate and underlying causes that wouldn't have died at that time if they hadn't become infected with the influenza virus in the period prior to their demise. Influenza is like heart disease or diabetes or cigarette smoking: a major cause…
revere | May 23, 2009Queens, a borough of the city of New York, seems to be a hotspot for swine flu and a New York Times reporter on the city beat, Anemona Hartocollis, has been writing very astute and perceptive pieces from there. Yesterday she had one on the problem posed by the "worried well" who are flooding Emergency Rooms in quest of reassurance. Articles about worried parents who bring relatively well kids to the Emergency Room (ER) are not uncommon. They usually include interviews with harassed and overburdened emergency room doctors and nurses dismayed at the unnecessary demand and its consequences for…
revere | May 22, 2009There is as yet no vaccine for the novel H1N1 (swine flu) pandemic strain of influenza now causing widespread illness in North America and what appears to be the start of growing outbreaks in Japan and parts of Europe (but check out this excellent piece over at ScienceInsider). WHO says most developing nations are not able to track influenza, so what is happening in Africa and parts of Asia is not known with any confidence. While the clinical illness from this virus doesn't seem very different than seasonal flu, the fact that most of the world's population has no immunity to it means there is…
revere | May 20, 2009A kind reader directed my attention late yesterday to an article on the Boston Globe's web site about three schools closing in Boston because of absenteeism from flu-like illnesses. I was struck by a comment made by a freshman at Boston Latin that seemed to get it exactly right:
The closing surprised freshman Wilhelmina Moen, who noted it was nice that authorities were concerned about the student's health.
"I'm not that worried," said Moen, who lives in Brighton. "It's the same thing as the other kind of flu. That flu kills too." (Stephen Smith, Andrew Ryan, Elizabeth Cooneym Boston.com)
So…
revere | May 18, 2009Five more schools in the New York City borough of Queens have closed because of suspected swine flu cases. Eleven schools have now been closed there and hundreds of students are down with a flu-like illness. Parents are understandably concerned, the more so because not many days ago Mayor Bloomberg and the city's health commissioner (just named by Obama as the next director of CDC) were reassuring city residents this was pretty much lie seasonal flu.
We thought that was something that might come back to bite them, and now it has:
The city’s schools seem to have become both a sentinel and an…
revere | May 17, 2009At Friday's press briefing on the swine flu outbreak, Canadian Press's Helen Branswell twice asked whether CDC's weekly flu surveillance data showing the uptick in swine flu but also an unexpected prevalence in seasonal influenza was an artifact of increased testing or something new and unusual. CDC's Dan Jernigan was not especially clear, but seemed to acknowledge there was a lot of seasonal flu around:
The CDC said part of the increase is certainly due to the fact that much more influenza testing is going on these days, because of concerns about swine flu. But the agency said it seems that…
revere | May 14, 2009A reader (hat tip River) sent me a link to a New York Times piece quoting a physician who recently saw swine flu cases in Mexico City. He called attention to what seemed like an anomalous clinical presentation of many cases. Besides a higher proportion of gastrointestinal symptoms (nausea, vomiting, diarrhea), Virginia Commonwealth infectious disease specialist Dr. Richard P. Wenzel was surprised that many cases, even severely ill ones, did not have fever:
Many people suffering from swine influenza, even those who are severely ill, do not have fever, an odd feature of the new virus that…
revere | May 13, 2009Flu can be a nasty illness, nasty enough to kill you. Pregnant women are at more risk than others because their physiology is altered. They are carrying a foreign body (the fetus) so their immune response is not the same, and their cardiovascular and respiratory physiology are also different. CDC is reporting about 20 swine flu cases in pregnant women, and late yesterday they gave a more detailed description of three cases, one of which ended fatally:
Patient A. On April 15, a woman aged 33 years at 35 weeks' gestation with a 1-day history of myalgias, dry cough, and low-grade fever was…
revere | May 12, 2009Trying to figure out where the incipient swine flu pandemic is heading and how fast it is heading there is shooting at a moving target, and this one is moving pretty fast. The best we can do at this point is use whatever information we have to make some educated guesses about different scenarios along with how likely various scenarios are. We used to do this on the back of an envelope, Now we use computer programs. I'm not sure we are doing much better (or much worse), but we can make use of more information and the answer looks prettier when displayed.
Expedited publication of such an…
revere | May 11, 2009Yesterday DemFromCT had another in his continuing series at DailyKos on Flu and You (Part VIII). He extended an earlier post (part II) on a critical piece of public health infrastructure, laboratory surveillance. One of the graphics is this chart of influenza positive tests reported to the CDC by the WHO/NREVSS collaborating laboratories:
What you see in this chart is a weekly record of what seasonal influenza types and subtypes are circulating in the community (influenza A/H1N1, A/H3N2, B; swine flu makes a late appearance, far right). Flu seasons differ on dominant subtypes, whether they…
revere | May 10, 2009The spate of swine flu articles in The New England Journal of Medicine last week included an important "Perspective, The Signature Features of Influenza Pandemics — Implications for Policy," by Miller, Viboud, Baliska and Simonsen. These authors are familiar to flu watchers as experienced flu epidemiologists and analysts of archival and other data. Analysis of archival data is sometimes described as archeo-epidemiologic research. In their NEJM article Miller et al. summarize what they see as some common features in the three flu pandemics of the last century (so the generalization that there…
revere | May 8, 2009Late yesterday The New England Journal of Medicine published a number of papers on the recent swine flu outbreak. The first paper, "Emergence of a Novel Swine-Origin Influenza A (H1N1) Virus in Humans" by large federal-state team of epidemiologists describes 642 confirmed cases in 41 states as of May 5, 2009, two days before publication. What I find remarkable is the speed the problem was recognized -- literally days. Identification of the virus was first made in the CDC laboratory on April 15, just 3 weeks ago. Now we are already reading scientific papers providing a wealth of detail.
Among…
revere | May 7, 2009It seems a conversation on one of the comment threads about "swine flu parties" at Effect Measure has made the New York Times:
One of the first open debates of the idea of intentional self-infection was on Effect Measure, a public health blog with many posts by thoughtful people who say they are clinicians, epidemiologists, veterinarians and other professionals, sometimes in government, but who post under pseudonyms to speak freely.
On April 28, a user calling herself OmegaMom posted: “Just a quick note — I just got a Tweet from a mom suggesting ‘swine flu parties’ because the U.S. version…
revere | May 7, 2009Breathing easier, may be an apt phrase for an almost audible collective sigh of relief. So far, the incipient swine flu pandemic is not extremely nasty. Is this perhaps premature? The world's premier scientific journal, Nature, and many flu scientists, suggest it is:
Complacency, not overreaction, is the greatest danger posed by the flu pandemic. That's a message scientists would do well to help get across.
[snip]
There is ample reason for concern: a new flu virus has emerged to which humans have no immunity, and it is spreading from person to person. That has happened only three times in the…
revere | May 6, 2009How fast flu spreads is related to how many susceptible people an infectious person can infect (a measure called R0) and also something called the serial interval. The serial interval is the average length of time between the start of one infection and the start of the infection of that case's infected contacts. The horter the serial interval the faster a virus can spread. So what is the serial interval for this virus and how can we determine it? The answer to the first question is the usual. We don't know yet. The answer to the second one tells us a little about why we don't know and why we…
tsmith | May 5, 2009
Now if he could just get his science straight when it comes to vaccination...but perhaps this mean he's changed his views on the germ theory?
(H/T Louis)
revere | May 5, 2009As I write this the US has 279 confirmed cases and one death from H1N1/2009 in 36 states. WHO has tallied 1085 1124 cases in 21 countries with 25 deaths. There is a backlog of samples waiting for confirmation, so by the time you read this the counters will probably have rolled upward, especially as state laboratories become facile with the new primers and are able to do their own confirmation. And predicting an increasing case count is about all anyone can say with certainty at this point. What we said once about flu pandemics can be said just as appropriately for the flu virus: "If you've…
revere | May 4, 2009Cytokine storm is a graphic phrase that doesn't do justice to the complexity of one of the things that made the 1918 H1N1 virus so virulent and is also implicated in the frightful case fatality of H5N1 ("bird flu"). The current H1N1/2009 is not showing a propensity to cause this nasty effect, but the subject has come up several times in the comments. The post I am sending you to was written just before the current outbreak. It is about recent work that is trying to unravel the mechanism behind the serious immune system dysregulation called cytokine storm. While it's mainly about cutting edge…
tsmith | May 4, 2009Back to the grind this week unfortunately, but the swine flu/H1N1 story is still developing and still fascinating. The most recent numbers show 286 confirmed US cases in 36 states.
There are many remaining questions on the evolution and epidemiology of this strain--and many pundits sure they know what's going to happen next. Mike takes one of them down--Wendy Orent, who I've blogged about previously. Orent is claiming (based on a black/white version of the evolution of virulence in pathogens) that the spread of this strain is attenuating the virus, and that future outbreaks will be…