Friday, June 01, 2007

TB or not...no, it's TB.


We have all been witness to the scare of drug resistant TB "on the loose." You need to say that is it is out there, just not here.

A troubling security aspect to this is how he got back here. He drove across the border, his passport randomly checked. That meant the flag on him was seen. But the guard doing the scan, who saw an order to hold and isolate, just figured that he didn't look sick, so didn't bother to act.

I'd complain some, but it seems the guard must have just followed his president's example.

Effect Measure has a look at the risk at issues of TB spreading on a plane.

It was only last week we posted about XDR-TB. Yesterday CDC warned passengers on two international flights -- Air France 385, Atlanta to Paris on May 12 and Czech Air 104, Prague to Canada on May 24 -- they may have been infected by another passenger who had Extensively Drug Resistant TB (XDR-TB). Reportedly authorities could not reveal which row the male passenger sat in as this would violate medical confidentiality laws (HIPAA). So anyone on the plane could think themselves at risk, although it was probably only those in the same row and several rows front and aft of the passenger who were really at risk. And the cabin crew, of course.

It's natural to think of an airplane as the ideal place to contract an infectious disease. After all, you are strapped in a seat in a narrow cylinder for hours at a time, next to people from diverse geographic origins, breathing recirculated air. If this isn't the perfect recipe for spreading an infectious disease, it is hard to think of what might be better. But in fact there is precious little evidence that airplane rides are a lottery ticket for a respiratory infection, as noted in a 2005 Commentary that accompanied Mangili and Gendreau's review of the subject (Commentary: Lancet. 2005 Mar 12-18;365(9463):917-9).

It turns out that while an airplane provides the smallest volume of air per person of any public space, the movement of air is transverse, i.e., from side to side, not along the length of the airplane. The air descends from the top of the cabin to the middle, sweeping in two circles on either side. Thus the people in the middle section of a wide body jet get the freshest air, with passengers seated to either side getting the air sweeping past the more medial seat mates. The poor soul on the window gets the air from everyone else in the row on their side of the plane (see figure 1 in Mangili and Gendreau). So the seat of the index case is probably critical, although this pattern is "on average." There is enough turbulence in cabin air to allow currents to go several rows front and aft. While it is true about 50% of the cabin air is recirculated, in all but the smallest regional jets it is passed through HEPA filters first. This was certainly true for the transatlantic planes in the current case.

There are a number of reports in the literature of infectious diseases contracted via airplane travel, including measles, influenza, TB and SARS. But not many. In general secondary cases were within a few rows of the index case, but in one notable instance, Air China flight 112 in 2003, SARS cases occurred in passengers seven rows in front and five rows behind the index case.

The paucity of cases in the literature might mean passenger to passenger transmission happens rarely, or it might merely be a reflection of the difficulty of detecting a disease cluster when all the contacts disperse widely upon reaching their destination. Since TB is largely a large droplet transmission, the belief that transmission is limited to those two rows in front and behind is probably justified.

Probably. But meanwhile the passengers have to be found, evaluated for infection and their contacts, likewise. Welcome to My World. Or should I say, Welcome to Our World. Because we are surely in it together.

They also look at the question of isolation and quarantine.

I'm not a lawyer and I don't play one on TV. But I think I know the difference between quarantine and isolation, and the widespread media reports that the Georgia resident with XDR-TB was the first person "quarantined" by the US government since 1963 didn't make sense. Quarantine means to segregate and possibly confine people who have been exposed to a contagious disease and therefore may become infectious themselves and spread it to others. But they are not sick. People who are segregated from the public and whose movement is restricted are under isolation, not quarantine. The Georgia resident has clearly been isolated, first in an isolation ward in a New York hospital and currently at Grady Memorial in Atlanta. Both isolation and quarantine are meant to stop the spread of contagious disease and are authorized under federal law: 42 U.S.C. Section 264.

As I understand it (and I would be glad to have any clarifications or corrections from a real lawyer), the law authorizes the government to isolate or quarantine a person or persons, the diseases and other details to be further set out in regulations or Executive Orders. The regulations are in the Code of Federal Regulations at 42 C.F.R., Parts 70 and 71. (cites and links courtesy CDC Public Health Law News).

Infectious tuberculosis is designated one of the diseases for which federal isolation and quarantine are authorized through Executive Order 13295. The other diseases are SARS, Cholera; Diphtheria; Plague; Smallpox; Yellow Fever; and Viral Hemorrhagic Fevers (Lassa, Marburg, Ebola, Crimean-Congo, South American, and others not yet isolated or named). The stipulation of infectious tuberculosis stems from the fact that most people infected with the tubercle bacillus never become sick or contagious. When I was in medical training it was more the rule than the exception for health care workers to convert from negative to positive skin test early on. I, myself, have been a positive reactor for more than 50 years. It is also very common to see scars from old TB lesions in the lungs of people who never knew they were infected and were never sick (latent TB). You are infectious if the TB organism can be found in your sputum, but often people are treated if they have a recent positive skin or blood test and a history suggestive of recent infection, e.g., they have been in contact with an infectious case. Thus positive reactors amongst the passengers in this case would likely be considered for immediate treatment, although the treatment regimen would have to be carefully considered as this is said to be an XDR organism.

According to CDC, this is the first time any of the regulations or Executive Order have been used for TB. The realization this was XDR-TB and the patient was traveling came to a head on a holiday weekend, compounding the matter. There is still a lot to learn about this episode and it is likely new procedures will be put in place as a result. We will learn in time if outright blunders were made, but we already know much needs to be done to make this system work in a timely way. We also want it to work in a way that doesn't make the protections themselves a problem.

An immediate reaction was that this individual should have been locked up -- forcibly detained, as a matter of policy. Let's assume he was highly infectious (possible, but not likely, in this case) and that you might have crossed paths with him on his travels. Maybe a bus, the same plane, the same airplane concourse. Of course if you are a good citizen, once you realized it you would turn yourself in (you would, wouldn't you?). At that point, should you be forcibly detained and tested? If not, why not? If you test positive -- which many people do, as I noted above -- should you then be locked up? After all, we now have a good argument that if he infected you, you have XDR TB. Of course it will take about six to eight weeks to find out, so we'll have to lock you up for a couple of months. Then if you are infected, treatment is a couple of years. Keep you locked up? If not, what makes you different?

More generally, what about anyone diagnosed with tuberculosis? Last year there were almost 14,000 TB diagnoses in the US. Since we don't know if one of those diagnosed might be drug resistant (although we know some will be), and by the time we find out, they will have infected others, should we lock them up too? All 14,000? If someone who has XDR TB is so dangerous they must be locked up, then isn't this what we must do? Or should we only lock up people who have been diagnosed with XDR TB -- something that happens only after they have been around and possibly infected others for months.

I don't know what the answer is. But "lock 'em up" isn't likely to be any better for TB than for HIV.
And on NPR today they had an interesting piece done by a woman who had tested positive for TB and the attitude she still faces. It was interesting as it was not active TB, but inactive. So she had come in contact with it at some point in her life. So the test was positive for her. She took antibiotics to kill any remnant in her body, and continues to get tested to be sure it never arises.

It struck we as I have had a similar experience. When I did all the test before entering college, I took that test. I got the injection under the skin, and I got the bump. So I was told I had an inactive bit in me. I got a prescription for the meds and to this day it is something I think and wonder about. When I get congested or have a little trouble breathing, could it be...?

In a sense it makes me think more of health care. Particularly getting some form of universal coverage started. At this time, I am working as a contracted part timer. That means I have no coverage, I haven't for a long while, including through a gall bladder removal. I also have a none too big bank account, and a car that needs to be fixed soon. Going in for a non emergency test is out of the question. And when you think of the large part of the population in the same straits, and worse...It should worry you.

One guy slipped over the border. But what about the masses inside already, untested and unknowing?

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