People went on red alert about SARS, where the fatality rate was approximately 10%. Bird flu doesn’t even spread between people (yet), but we’re on red alert about bird flu. Don’t get me wrong. Prevention is way better than cure. But it would make sense to deal with actual current threats before panicking about possible ones.
Tuberculosis is a much bigger problem than SARS, and it’s here, now, and killing millions. Untreated TB has a fatality rate of around 55%. TB treatment in the days before drugs reduced that rate to around 30%. In developed countries, with anti-TB drugs, the fatality rate was around 7%. (TB stats from the CDC.) Most of the current fatalities worldwide are people who had ordinary TB and couldn’t afford the cure. From a callous perspective, that’s not a problem in developed countries. But the drug-resistant strains that evolve in people who can’t or don’t take the full course of treatment is everybody’s problem.
As if that wasn’t bad enough, drug-resistant TB just took a turn for the worse.
There are three different factors to keep in mind with bacteria and viruses: virulence (the severity of the symptoms caused by that specific strain), infectivity (how likely you are to catch it), and drug resistance. These are not correlated. A disease can be virulent, but not highly infective or drug resistant, or totally resistant to drugs, but not virulent, and so on.
So far, drug resistant TB has been rather low on infectivity. (Even bacteria have a hard time being good at everything all at once.) The guy I will always think of as The TB Lawyer had an extremely drug resistant strain (XDR, worse than the MDR, multiply drug resistant, strains you commonly hear about). But it was a strain with low infectivity. I guess, when they told him that, he heard only the good news, and figured he was good to go. [Update: Turns out he has MDR TB. See footnote for a bit more detail.] I haven’t seen anything about where he picked it up, which seems like an interesting question, or how virulent it is. They say he has a 30% chance of succumbing, which is what you’d expect for “normally” virulent TB when drugs aren’t — or as in this case — can’t be used.
Well, now comes news from South Africa of a hyper-virulent, extremely drug resistant strain. When these medical types say hyper-virulent, they mean it. Fifty two out of the 53 people with confirmed diagnoses died. Average survival after the diagnostic samples were taken was 25 days. Median survival (i.e. the length of time the largest number of people survived) was 16 days.
Now, these particular people also had AIDS, which doesn’t help, but this is not the way AIDS patients react to “normal” TB. There is no reason to think the hyper-virulence would be different in people without AIDS. It’s also not an experiment where I’d like to be the guinea pig.
The strain is not, from what I see, hyper-infective. If it’s like “normal” TB, it spreads rather like a cold.
The World Health Organization is so freaked out by this combination of characteristics, they’d like to see people go on a SARS-type alert to prevent global transmission. They also want South Africa to receive as much aid as is necessary to make sure all cases are identified, isolated, and treated. See the excellent PLoS article for that and many other links.
(Factoid via CDC, March 2006: “XDR TB was identified in all regions but was most common in South Korea … and countries of eastern Europe/western Asia.” These strains are not (yet) hyper-virulent.)
Following the steps indicated by the WHO would be the intelligent thing to do. Not to panic. Not to hoard (probably useless) drugs, not to join Cheney in a bunker and shoot all comers. No, just to address the issue and do what it takes.
Instead, the reaction in the developed world could be summarized as, “Another disease in Africa?” *Yawn*
We won’t be yawning when (it’s when, not if) the strain gets here. Then we’ll be flapping around in a useless panic, probably with fascist overtones, if past experience is any guide.
(MDR TB: resistant to the two main TB drugs (rifampicin and isoniazid). XDR TB is resistant to those as well as the quinolone class of antibiotics, and at least one of the second-line antibiotics (kanamycin, capreomycin, or amikacin). (These drugs are more toxic to the patient and usually(?) or always(?) have to be given by IV.) The older definition of XDR TB was resistance to three or more of the second-line drugs. (From Wikipedia) The definitions are clearly divided, but the bacteria are not. Resistance is not all or nothing. So a TB infection could be 100% resistant to the two main drugs, 90% resistant to one of the second-line drugs, 80% to another one, 65% to another one, and so on. What are you going to call that? MDR? XDR? I suspect this is the problem the CDC was having. They tested the diagnostic samples, found plenty of resistance, and tried to find the guy. Further tests showed some susceptibility, so now they’re calling it MDR.)