Hacker News Reader

Comment by amluto | Hacker News Reader

A mystery not mentioned in the article: why is TB so unusual in places like the US? The US does almost nothing to control TB. We don’t vaccinate. We don’t routinely test (except in special cases, but those cover very little of the population). We don’t treat latent cases unless they somehow get noticed. And yet the incidence of symptomatic TB is low, and there’s no sign of TB developing resistance to whatever the US is accidentally doing right.

View on HN

TB is almost the archetypal disease of poverty.

Living on top of each other, especially in childhood & adolescence, combined with other environmental and health factors explains almost all of it. If you’re malnourished and your immune system is in bad shape, you’re at risk. If you have HIV, you’re at risk and so on.

That’s still not an explanation. Kids in the US spend a lot of time with other kids at daycare and school. It’s a transmittable bacterial disease. Why aren’t people in the US getting it more? Are you saying you have to be mal/undernourished to get it?

Malnourishment is a big part according to the WHO [1]

I’m no expert but I also suspect access to medical care is also a big part, as typically only active cases spread the disease. If you are symptomatic and get some antibiotics, you might not spread it to very many people. If you’re symptomatic and go without treatment for ages, then you might spread it to loads of other people.

As we learned during covid, small differences in R value massively change the prevalence over time.

https://bmcpublichealth.biomedcentral.com/articles/10.1186/s...

Unhealthy people are more vulnerable to TB, absolutely. Infections in general are more prevalent in people who are underfed, or living in bad conditions. Other risk factors are exactly what you would expect: smoking, drinking, bad fitness level, and being young or old.

TB rates are basically a function of 1. how immune compromised your population is, and 2. How much access to healthcare there is in the country (poverty, basically).

The majority of healthy people develop a latent infection, and won't manifest symptoms in their lifetimes. The bacteria are encapsulated into nodules by the immune system, which weaken if the immune system weakens. The bacteria escape and active symptomatic infection occurs.

Yeah but the US has very low levels of latent TB in the population at only 4%. Compared that to places like Brazil where 40% of the population has latent TB. It’s not the climate because in Russia 80% of the population has latent TB.

Yes, and it's a self-perpetuating cycle. If so few people have latent TB, fewer people develop active TB that will go on to infect others. As other comments have mentioned, poverty and its resultant poor health is the biggest correlation for developing active TB. I wonder if most of the Russian latent infections happened during the Soviet/Post Soviet collapse era, with newer latent infections falling off as quality of life improved over time?

quality of life improving in Russia is a very risky statement. Soviets manipulated statistics and so does current Russian government.

In order to get latent TB, you need exposure to someone with active TB. If someone with active TB meets the healthcare system, you get a rapid response from health departments. In May 2024, the Long Beach, CA declared a public health emergency [1] based on a cluster of 14 cases. This kind of reaction is typical and makes it difficult to spread to others, and keeps the levels of latent TB low.

[1] https://www.longbeach.gov/press-releases/official-city-of-lo...

80% sounds like a BS number. It's cited on Wikipedia, but references are either "opinions" or do not contain such information at all.

A proper study [1] shows mean infection rate of ~20% in the worst regions (Far East and North) with the highest rate up to 47%. The situation should be better in the western regions. For comparison, in the US studies show ~4% infection rate [2], so situation in Russia is relatively bad, but improves steadily since 90s and it's far from being catastrophic as the 80% number paints it.

[1]: https://www.tibl-journal.com/jour/article/view/1706

[2]: https://www.cdc.gov/tb/hcp/clinical-overview/latent-tubercul...

I guess it depends on what’s considered trustworthy. I wouldn’t trust a Russian paper as far as you could throw it unless it was in math or physics.

Russia actually spent quite a lot of resources on TB, especially during the late Soviet and the early Russian history.

All children and professionals working with children are receiving yearly TB testing ("Mantoux test"). Prisons used to be a major vector, but that was reduced by doing TB prevention (antibiotics).

Nobody likes getting TB.

But you will trust any unsubstantiated slander disseminated in mass media by interested parties as long as it paints Russia in a bad light. Got it.

Russia did this to themselves. Objectively, for what it once was Russia has horrific metrics around healthcare, alcohol consumption, HIV, drug use, food prices, human rights or any kind of sustainability initiative.

I was exposed to TB at Children's Hospital in Washington DC and it was only because I was seeking a part-time job at another hospital while in grad school that I became aware. Got the bubble at the public health department and by the time I drove 40 minutes home, I was clearly positive, so off to Children's I went to have the test read. Because I was a volunteer, I was able to be xrayed immediately and prescribed drugs to take for 9 months. And then, of course, the hospital came after me for the cost of the xray, arguing that I could have been exposed shopping at Talbot's.

I was not surprised to have been exposed. I volunteered a lot of hours in the Children's ED so I had much greater exposure than other people my age who were doing whatever you do when you're 30. I think the doctors and nurses were surprised that I did not freak out and docs to this day are a little surprised I didn't. It was inactive and I was diligent taking the meds.

All this said, the point is that more needs to be done in the US, particularly when we know where the greatest exposure happens.

Spitting has become socially unacceptable in the US. This is due to large scale "anti-spitting" campaigns in the early 1900.

In the 19th century when spittoons were a thing in the US, TB ran rampant.

There's also the widespread antibiotic use. The widespread prescription of Doxycycline for everything inadvertently does a lot.

Overlay TB with poverty (or more accurately, per capita GDP) on the map.

There are number of correlations with unhealthy activities like smoking, drinking, fitness, etc... but the best indicator is if you live in poverty, and/or if you're country is poor. Poor areas of rich countries have higher TB, and poor countries in general have higher incidences of poverty. Basically, less access to healthcare and bad living conditions.

This is a good study here that explain the individual risk factors, but the available maps also show a pretty clear pattern: https://bmcpublichealth.biomedcentral.com/articles/10.1186/s...

My first job as a teen in 1982 was at a restaurant. I had to get a "food handler's permit" from the local health department, which was mainly a TB test, maybe also a hepatitis test. Those permits are no longer required.

My understanding is that TB doesn't spread while latent, it needs to develop into active TB to spread.

The US healthcare system is tuned into TB cases and will alert local health officials to do contact tracing, outreach, and follow up with confirmed cases when they pop up.

Healthcare and childcare workers are routinely tested for TB in areas with recent spread.

Doing screening on the general population doesn't seem necessary, given the low estimated % of people with latent infections and the low estimated % of latent infections that will develop into active infections. It may make sense to screen more people that have a higher risk if they develop active TB or are at a higher risk of exposure.

Certainly, increased screening or vaccination would result in improved outcomes for people whose TB infection was averted. But those have to be weighed against the negative outcomes from side effects of screening/treatment and vaccination.

While I can't deny the argument that US national anti-TB efforts have become fragmented, possibly as a result of lower incidence, BCG isn't an especially protective vaccine against pulmonary disease and can interfere with TB skin testing, which even in this age of generally available blood QuantiFERON testing is still not uncommon. BCG does have greater value in high-risk countries, and it may be most useful for kids in those regions where TB meningitis is a bigger threat. It doesn't make a lot of sense in a low-burden country, but perhaps one day we'll have a better one.

- working in TB control since 2006

Less public transport perhaps? I remember studies showing strong correlation even though causation can be questionable (less protected member of society in the first place). And anecdotally the only person I know with TB never had known cases neither at home nor at work, which basically leaves the public transportation (which he was using 2-4 times a day at the time) as the most likely source.

Another idea could be "better climate" but it's not obvious when I look on the world map of TB incidence.

Reply on news.ycombinator.com