Category: Medicine
The cocaine problem seems to be getting worse again
Colombian coca cultivation fell dramatically between 2000 and 2015, a period that saw intense U.S.-backed eradication and interdiction efforts. That progress reversed in 2015, when peace talks and legal rulings in Colombia opened enforcement gaps. Coca plantation has since increased to record levels, which coincided with a sharp rise in cocaine-related overdose deaths in the U.S. We estimate how much of that rise can be causally attributed to Colombia’s new coca boom. Leveraging the unforeseen coca supply shock and cross-county differences in pre-shock cocaine exposure, we find that the surge in supply caused an immediate rise in overdose mortality in the U.S. Our analysis estimates on the order of 1,000–1,500 additional U.S. deaths per year in the late 2010s can be attributed to Colombia’s cocaine boom. Implicit annual loss in American statistical life values about $48,000 per hectare of cultivation in Colombia. If left untamed, the current level of coca cultivation (over 230,000 ha in 2022) may impose on the order of $10 billion per year in costs via overdose fatalities.
That is from a new NBER working paper by Xinming Du, Benjamin Hansen, Shan Zhang, and Eric Zou.
I Regret to Inform You that the FDA is FDAing Again
I had high hopes and low expectations that the FDA under the new administration would be less paternalistic and more open to medical freedom. Instead, what we are getting is paternalism with different preferences. In particular, the FDA now appears to have a bizarre anti-vaccine fixation, particularly of the mRNA variety (disappointing but not surprising given the leadership of RFK Jr.).
The latest is that the FDA has issued a Refusal-to-File (RTF) letter to Moderna for their mRNA influenza vaccine, mRNA-1010. An RTF means the FDA has determined that the application is so deficient it doesn’t even warrant a review. RTF letters are not unheard of, but they’re rare—especially given that Moderna spent hundreds of millions of dollars running Phase 3 trials enrolling over 43,000 participants based on FDA guidance, and is now being told the (apparently) agreed-upon design was inadequate.
Moderna compared the efficacy of their vaccine to a standard flu vaccine widely used in the United States. The FDA’s stated rationale is that the control arm did not reflect the “best-available standard of care.” In plain English, that appears to mean the comparator should have been one of the ACIP-preferred “enhanced” flu vaccines for adults 65+ (e.g., high-dose/adjuvanted) rather than a standard-dose product.
Out of context, that’s not crazy but it’s also not necessarily wise. There is nothing wrong with having multiple drugs and vaccines, some of which are less effective on average than others. We want a medical armamentarium: different platforms, different supply chains, different side-effect profiles, and more options when one product isn’t available or isn’t a good fit. The mRNA vaccines, for example, can be updated faster than standard vaccines, so having an mRNA option available may produce superior real-world effectiveness even if it were less efficacious in a head-to-head trial.
In context, this looks like the regulatory rules of the game are being changed retroactively—a textbook example of regulatory uncertainty destroying option value. STAT News reports that Vinay Prasad personally handled the letter and overrode staff who were prepared to proceed with review. Moderna took the unusual step of publicly releasing Prasad’s letter—companies almost never do this, suggesting they’ve calculated the reputational risk of publicly fighting the FDA is lower than the cost of acquiescing.
Moreover, the comparator issue was discussed—and seemingly settled—beforehand. Moderna says the FDA agreed with the trial design in April 2024, and as recently as August 2025 suggested it would file the application and address comparator issues during the review process.
Finally, Moderna also provided immunogenicity and safety data from a separate Phase 3 study in adults 65+ comparing mRNA-1010 against a licensed high-dose flu vaccine, just as FDA had requested—yet the application was still refused.
What is most disturbing is not the specifics of this case but the arbitrariness and capriciousness of the process. The EU, Canada, and Australia have all accepted Moderna’s application for review. We may soon see an mRNA flu vaccine available across the developed world but not in the United States—not because it failed on safety or efficacy, but because FDA political leadership decided, after the fact, that the comparator choice they inherited was now unacceptable.
The irony is staggering. Moderna is an American company. Its mRNA platform was developed at record speed with billions in U.S. taxpayer support through Operation Warp Speed — the signature public health achievement of the first Trump administration. The same government that funded the creation of this technology is now dismantling it. In August, HHS canceled $500 million in BARDA contracts for mRNA vaccine development and terminated a separate $590 million contract with Moderna for an avian flu vaccine. Several states have introduced legislation to ban mRNA vaccines. Insanity.
The consequences are already visible. In January, Moderna’s CEO announced the company will no longer invest in new Phase 3 vaccine trials for infectious diseases: “You cannot make a return on investment if you don’t have access to the U.S. market.” Vaccines for Epstein-Barr virus, herpes, and shingles have been shelved. That’s what regulatory roulette buys you: a shrinking pipeline of medical innovation.
An administration that promised medical freedom is delivering medical nationalism: fewer options, less innovation, and a clear signal to every company considering pharmaceutical investment that the rules can change after the game is played. And this isn’t a one-product story. mRNA is a general-purpose platform with spillovers across infectious disease and vaccines for cancer; if the U.S. turns mRNA into a political third rail, the investment, talent, and manufacturing will migrate elsewhere. America built this capability, and we’re now choosing to export it—along with the health benefits.
Immigration and health for elderly Americans
We measure the impact of increased immigration on mortality among elderly Americans, who rely on the immigrant-intensive health and long-term care sectors. Using a shift-share approach we find a strong impact of immigration on the size of the immigrant care workforce: admitting 1,000 new immigrants would lead to 142 new foreign healthcare workers, without evidence of crowd out of native health care workers. We also find striking effects on mortality: a 25% increase in the steady state flow of immigrants to the US would result in 5,000 fewer deaths nationwide. We identify reduced use of nursing homes as a key mechanism driving this result.
That is from a new NBER working paper by
Trump’s Pharmaceutical Plan
Pharmaceuticals have high fixed costs of R&D and low marginal costs. The first pill costs a billion dollars; the second costs 50 cents. That cost structure makes price discrimination—charging different customers different prices based on willingness to pay—common.
Price discrimination is why poorer countries get lower prices. Not because firms are charitable, but because a high price means poorer countries buy nothing, while any price above marginal cost is still profit. This type of price discrimination is good for poorer countries, good for pharma, and (indirectly) good for the United States: more profits mean more R&D and, over time, more drugs.
The political problem, however, is that Americans look abroad, see lower prices for branded drugs, and conclude that they’re being ripped off. Riding that grievance, Trump has demanded that U.S. prices be no higher than the lowest level paid in other developed countries.
One immediate effect is to help pharma in negotiations abroad: they can now credibly say, “We can’t sell to you at that discount, because you’ll export your price back into the U.S.” But two big issues follow.
First, this won’t lower U.S. prices on current drugs. Firms are already profit-maximizing in the U.S. If they manage to raise prices in France, they don’t then announce, “Great news—now we’ll charge less in America.” The potential upside of the Trump plan isn’t lower prices but higher pharma profits, which strengthens incentives to invest in R&D. If profits rise, we may get more drugs in the long run. But try telling the American voter that higher pharma profits are good.
The second issue is that the plan can backfire.
In our textbook, Modern Principles, Tyler and I discuss almost exactly this scenario: suppose policy effectively forces a single price across countries. Which price do firms choose—the low one abroad or the high one in the U.S.? Since a large share of profits comes from the U.S., they’re likely to choose the high price:
Pfizer CEO Albert Bourla was even more direct, saying it is time for countries such as France to pay more or go without new drugs. If forced to choose between reducing U.S. prices to France’s level or stopping supply to France, Pfizer would choose the latter, Bourla told reporters at a pharma-industry conference.
So the real question is: will other countries pay?
If France tried to force Americans to pay more to subsidize French price controls, U.S. voters would explode. Yet that’s essentially what other countries are being told but in reverse: “You must pay more so Americans can pay less.” Other countries are already stingier than the U.S., and they already bear costs for it—new drugs arrive more slowly abroad than here. Some governments may decide—foolishly, but understandably—that paying U.S.-level prices is politically impossible. If so, they won’t “harmonize upward.” They’ll follow the European way: ration, delay and go without.
In that case, nobody wins. Pharma profits fall, R&D declines, U.S. prices don’t magically drop, and patients abroad get fewer new drugs and worse care. Lose-lose-lose.
We don’t know the equilibrium, but lose-lose-lose is entirely plausible. Switzerland, for example, does not seem willing to pay more:
Yet Switzerland has shown little political willingness to pay more—threatening both the availability of medications in the country and its role as a global leader in developing therapies. Drug prices are the primary driver of the increasing cost of mandatory health coverage, and the topic generates heated debate during the annual reappraisal of insurance rates. “The Swiss cannot and must not pay for price reductions in the USA with their health insurance premiums,” says Elisabeth Baume-Schneider, Switzerland’s home affairs minister.
If many countries respond like Switzerland—and Trump’s unpopularity abroad doesn’t help—the sector ends up less profitable and innovation slows. Voters may feel less “ripped off,” but they’ll be buying that feeling with fewer drugs and sicker bodies.
The Effects of Ransomware Attacks on Hospitals and Patients
As cybercriminals increasingly target health care, hospitals face the growing threat of ransomware attacks. Ransomware is a type of malicious software that prevents users from accessing electronic systems and demands a ransom to restore access. We create and link a database of hospital ransomware attacks to Medicare claims data. We quantify the effects of ransomware attacks on hospital operations and patient outcomes. Ransomware attacks decrease hospital volume by 17–24 percent during the initial attack week, with recovery occurring within 3 weeks. Among patients already admitted to the hospital when a ransomware attack begins, in-hospital mortality increases by 34–38 percent.
That is by Hannah Neprash, Claire McGlave, and Sayeh Nikpay, recently published in American Economic Journal: Economic Policy.
What happens when dating goes online?
This paper studies how online dating platforms have impacted marital outcomes, assortative matching, and sexually transmitted disease (STD) rates in the United States. We construct county-level measures of online dating usage using data from website-based platforms (2002-2013) and mobile app-based platforms (2017-2023). Leveraging county-level variation and an instrumental variable strategy, we show in the desktop era, a 1% increase in online dating sessions raises divorce rates by 0.50%, while in the mobile era, a 1% increase in online dating activity lowers marriage and divorce rates by 0.40% and 0.33%, respectively. We also document shifts in assortative matching. Desktop sites reduce sorting along education and employment dimensions, whereas mobile sites reduce sorting by employment, but increase sorting by race. Across both eras, we find no evidence that greater online dating usage increases average STD rates. Average effects are negative or statistically insignificant, but are positive for some subpopulations. We develop a search and matching model where technological changes impact search costs, market size, and market noise can explain our empirical findings.
That is from a new paper by Daniel Ershov, Jessica Fong, and Pinar Yildirim. Via the excellent Kevin Lewis.
AI Physicians At Last
In 2004 (!) I wrote:
Many people complain that medicine is too impersonal. I think it is not impersonal enough. I have nothing against my physician (a local magazine says he is one of the best in the area) but I would prefer to be diagnosed by a computer. A typical physician spends most of the day playing twenty questions. Where does it hurt? Do you have a cough? How high is the patient’s blood pressure? But an expert system can play twenty questions better than most people. An expert system can use the best knowledge in the field, it can stay current with the journals, and it never forgets.
It took longer than it should have, but we are finally here. Today, most people already use AI to help diagnose and manage medical conditions, and now:
Utah is letting artificial intelligence — not a doctor — renew certain medical prescriptions. No human involved.
It’s a pilot program for routine renewals but a welcome start. The AMA, of course, is not pleased.
In a statement, Dr. John Whyte, CEO and executive vice president at the American Medical Association, said: “While AI has limitless opportunity to transform medicine for the better, without physician input it also poses serious risks to patients and physicians alike.”
One concern is misuse or abuse, including the possibility that people struggling with addiction could try to game automated systems to obtain drugs inappropriately. Another concern is missing subtle clinical red flags or drug interactions that a doctor would catch.
It’s amazing that anyone can say these things with a straight face. As far as I know, AI has never run a pill mill, unlike human physicians. And the AI
“missing subtle clinical red flags or drug interactions that a doctor would catch.” Is this a joke?
Direct and Indirect Effects of Vaccines: Evidence from COVID-19
Sorry people, but the verdict on this one continues to come in:
We estimate direct and indirect vaccine effectiveness and assess how far the infection-reducing externality extends from the vaccinated, a key input to policy decisions. Our empirical strategy uses nearly universal microdata from a single state and relies on the six-month delay between 12- and 11-year-old COVID vaccine eligibility. Vaccination reduces cases by 80 percent, the direct effect. This protection spills over to close contacts, producing a household-level indirect effect about three-fourths as large as the direct effect. However, indirect effects do not extend to schoolmates. Our results highlight vaccine reach as important to consider when designing policy for infectious disease.
That is from American Economic Journal: Applied Economics, by Seth Freedman, Daniel W. Sacks, Kosali Simon, and Coady Wing. So many different methods and papers are pointing in the same direction…
Autism Hasn’t Increased
Autism diagnoses have increased but only because of progressively weaker standards for what counts as autism.
The autistic community is a large, growing, and heterogeneous population, and there is a need for improved methods to describe their diverse needs. Measures of adaptive functioning collected through public health surveillance may provide valuable information on functioning and support needs at a population level. We aimed to use adaptive behavior and cognitive scores abstracted from health and educational records to describe trends over time in the population prevalence of autism by adaptive level and co-occurrence of intellectual disability (ID). Using data from the Autism and Developmental Disabilities Monitoring Network, years 2000 to 2016, we estimated the prevalence of autism per 1000 8-year-old children by four levels of adaptive challenges (moderate to profound, mild, borderline, or none) and by co-occurrence of ID. The prevalence of autism with mild, borderline, or no significant adaptive challenges increased between 2000 and 2016, from 5.1 per 1000 (95% confidence interval [CI]: 4.6–5.5) to 17.6 (95% CI: 17.1–18.1) while the prevalence of autism with moderate to profound challenges decreased slightly, from 1.5 (95% CI: 1.2–1.7) to 1.2 (95% CI: 1.1–1.4). The prevalence increase was greater for autism without co-occurring ID than for autism with co-occurring ID. The increase in autism prevalence between 2000 and 2016 was confined to autism with milder phenotypes. This trend could indicate improved identification of milder forms of autism over time. It is possible that increased access to therapies that improve intellectual and adaptive functioning of children diagnosed with autism also contributed to the trends.
The data is from the US CDC.
Hat tip: Yglesias who draws the correct conclusion:
Study confirms that neither Tylenol nor vaccines is responsible for the rise in autism BECAUSE THERE IS NO RISE IN AUTISM TO EXPLAIN just a change in diagnostic standards.
Earlier Cremieux showed exactly the same thing based on data from Sweden and earlier CDC data.
Happy New Year. This is indeed good news, although oddly it will make some people angry.
The Hainan Free Trade Port
Earlier I wrote about China’s Libertarian City, Boao Hope City (officially the Boao Lecheng International Medical Tourism Pilot Zone), China’s first special economic zone for advanced healthcare. Boao Hope City is following the peer approval model I have long argued for:
Daxue: Medical institutions within the zone can import and use pharmaceuticals and medical devices already available in other countries as clinically urgent items before obtaining approval in China. This allows domestic patients to access innovative treatments without the need to travel abroad…. The medical products to be used in the pilot zone must possess a CE mark, an FDA license, or PMDA approval, which respectively indicate that they have been approved in the European Union, the US, and Japan for their safe and effective use.
Boao Hope City is part of the larger Hainan Free Trade Zone. Hainan is a large island off China’s Southern Coast, often called the Hawaii of China. The entire island is being turned into the world’s largest free trade zone. As of Dec. 18, 2025, Hainan now boasts:
- Expanded “Zero-Tariff” Coverage…“zero-tariff” eligible goods expand from about 1,900 to approximately 6,600 tariff lines, increasing coverage from 21% to 74% of total import/export items, encompassing most production equipment and raw materials. This exemption applies to import tariffs, import VAT, and consumption tax, potentially saving enterprises about 20% in tax costs on imported equipment.
- Optimized “Tariff Exemption for Value-added Processing” Policy: One of the most transformative measures, this policy sees significantly relaxed restrictions (e.g., on core business income ratios) and now allows cumulative value-added calculation across upstream and downstream enterprises. This makes it easier for businesses to meet the “over 30% value-added” threshold for tariff exemption when selling finished products into the mainland market. Companies can ship primary products or components to Hainan for substantial processing; if the value-added meets the standard, the final products can enter the mainland market tariff-free.
- “Dual 15%” Tax Incentives as a Long-term Advantage: Encouraged industries registered and substantively operating in the Hainan FTP enjoy a reduced 15% corporate income tax rate. Eligible high-end and in-demand talents benefit from an individual income tax exemption for the portion exceeding 15%, providing long-term, stable fiscal predictability.
- Enhanced Trade and Investment Liberalization/Facilitation: Measures include implementing a negative list for cross-border trade in services, relaxing foreign investment access, adopting a “commitment-based registration system” for business setup, and streamlining procedures. A visa-free policy for nationals of 59 countries is in effect, with further eased entry-exit restrictions for business personnel.
An RCT on AI and mental health
Young adults today face unprecedented mental health challenges, yet many hesitate to seek support due to barriers such as accessibility, stigma, and time constraints. Bite-sized well-being interventions offer a promising solution to preventing mental distress before it escalates to clinical levels, but have not yet been delivered through personalized, interactive, and scalable technology. We conducted the first multi-institutional, longitudinal, preregistered randomized controlled trial of a generative AI-powered mobile app (“Flourish”) designed to address this gap. Over six weeks in Fall 2024, 486 undergraduate students from three U.S. institutions were randomized to receive app access or waitlist control. Participants in the treatment condition reported significantly greater positive affect, resilience, and social well-being (i.e., increased belonging, closeness to community, and reduced loneliness) and were buffered against declines in mindfulness and flourishing. These findings suggest that, with purposeful and ethical design, generative AI can deliver proactive, population-level well-being interventions that produce measurable benefits.
That is from a new paper by Julie Y.A. Cachia, et.al. A single paper or study is hardly dispositive, even when it is an RCT. But you should beware of those, such as Jon Haidt and Jean Twenge, who are conducting an evidence-less jihad against AI for younger people.
Via the excellent Kevin Lewis.
Is involuntary hospitalization working?
From Natalia Emanuel, Valentin Bolotnyy, and Pim Welle:
The involuntary hospitalization of people experiencing a mental health crisis is a widespread practice, as common in the US as incarceration in state and federal prisons and 2.4 times as common as death from cancer. The intent of involuntary hospitalization is to prevent individuals from harming themselves or others through incapacitation, stabilization and medical treatment over a short period of time. Does involuntary hospitalization achieve its goals? We leverage quasi-random assignment of the evaluating physician and administrative data from Allegheny County, Pennsylvania to estimate the causal effects of involuntary hospitalization on harm to self (proxied by death by suicide or overdose) and harm to others (proxied by violent crime charges). For individuals whom some physicians would hospitalize but others would not, we find that hospitalization nearly doubles the probability of being charged with a violent crime and more than doubles the probability of dying by suicide or overdose in the three months after evaluation. We provide evidence of housing and earnings disruptions as potential mechanisms. Our results suggest that on the margin, the system we study is not achieving the intended effects of the policy.
Here is the abstract online at the AEA site. I am looking forward to seeing more of this work.
GDPR is worse than you had thought
We examine how data privacy regulation affects healthcare innovation and research collaboration. The European Union’s General Data Protection Regulation (GDPR) aims to enhance data security and individual privacy, but may also impose costs to data collection and sharing critical to clinical research. Focusing on the pharmaceutical sector, where timely access and the ability to share patient-level data plays an important role drug development, we use a difference-in-differences design exploiting variation in firms’ pre-GDPR reliance on EU trial sites. We find that GDPR led to a significant decline in clinical trial activity: affected firms initiated fewer trials, enrolled fewer patients, and operated at fewer trial sites. Overall collaborative clinical trials also declined, driven by a reduction in new partnerships, while collaborations with existing partners modestly increased. The decline in collaborations was driven among younger firms, with little variation by firm size. Our findings highlight a trade- off between stronger privacy protections and the efficiency of healthcare innovation, with implications for how regulation shapes the rate and composition of subsequent R&D.
That is from Jennifer Kao and Sukhun Kang, here is the online abstract for the AEA meetings.
Crime and the Welfare State
Several recent papers claim that expanding programs like Medicaid reduces crime (e.g. here). I’ve been skeptical, not because of weaknesses in any particular paper, but just because the results feel a bit too aligned with social-desirability bias and we know that the underlying research designs can be fragile. As a result, my priors haven’t moved much. The first paper using a genuine randomized controlled trial now reports no effect of Medicaid expansion on crime.
Those involved with the criminal justice system have disproportionately high rates of mental illness and substance-use disorders, prompting speculation that health insurance, by improving treatment of these conditions, could reduce crime. Using the 2008 Oregon Health Insurance Experiment, which randomly made some low-income adults eligible to apply for Medicaid, we find no statistically significant impact of Medicaid coverage on criminal charges or convictions. These null effects persist for high-risk subgroups, such as those with prior criminal cases and convictions or mental health conditions. In the full sample, our confidence intervals can rule out most quasi-experimental estimates of Medicaid’s crime-reducing impact.
Finkelstein, Miller, and Baicker (WP).
It could still be the case that very targeted interventions–say making sure that released criminals get access to mental health care–could do some good but there’s unlikely to be any general positive effect.
A similar story is found in Finland where a large RCT on a guaranteed basic income found zero effect on crime
This paper provides the first experimental evidence on the impact of providing a guaranteed basic income on criminal perpetration and victimization. We analyze a nationwide randomized controlled trial that provided 2,000 unemployed individuals in Finland with an unconditional monthly payment of 560 Euros for two years (2017-2018), while 173,222 comparable individuals remained under the existing social safety net. Using comprehensive administrative data on police reports and district court trials, we estimate precise zero effects on criminal perpetration and victimization. Point estimates are small and statistically insignificant across all crime categories. Our confidence intervals rule out reductions in perpetration of 5 percent or more for crime reports and 10 percent or more for criminal charges.
My 2011 Review of Contagion
I happened to come across my 2011 review of the Steven Soderberg movie, Contagion and was surprised at how much I was thinking about pandemics prior to COVID. In the review, I was too optimistic about the CDC but got the sequencing gains right. I continue to like the conclusion even if it is a bit too clever by half. Here’s the review (no indent):
Contagion, the Steven Soderberg film about a lethal virus that goes pandemic, succeeds well as a movie and very well as a warning. The movie is particularly good at explaining the science of contagion: how a virus can spread from hand to cup to lip, from Kowloon to Minneapolis to Calcutta, within a matter of days.
One of the few silver linings from the 9/11 and anthrax attacks is that we have invested some $50 billion in preparing for bio-terrorism. The headline project, Project Bioshield, was supposed to produce vaccines and treatments for anthrax, botulinum toxin, Ebola, and plague but that has not gone well. An unintended consequence of greater fear of bio-terrorism, however, has been a significant improvement in our ability to deal with natural attacks. In Contagion a U.S. general asks Dr. Ellis Cheever (Laurence Fishburne) of the CDC whether they could be looking at a weaponized agent. Cheever responds:
Someone doesn’t has to weaponize the bird flu. The birds are doing that.
That is exactly right. Fortunately, under the umbrella of bio-terrorism, we have invested in the public health system by building more bio-safety level 3 and 4 laboratories including the latest BSL3 at George Mason University, we have expanded the CDC and built up epidemic centers at the WHO and elsewhere and we have improved some local public health centers. Most importantly, a network of experts at the department of defense, the CDC, universities and private firms has been created. All of this has increased the speed at which we can respond to a natural or unnatural pandemic.
In 2009, as H1N1 was spreading rapidly, the Pentagon’s Defense Threat Reduction Agency asked Professor Ian Lipkin, the director of the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health, to sequence the virus. Working non-stop and updating other geneticists hourly, Lipkin and his team were able to sequence the virus in 31 hours. (Professor Ian Sussman, played in the movie by Elliott Gould, is based on Lipkin.) As the movie explains, however, sequencing a virus is only the first step to developing a drug or vaccine and the latter steps are more difficult and more filled with paperwork and delay. In the case of H1N1 it took months to even get going on animal studies, in part because of the massive amount of paperwork that is required to work on animals. (Contagion also hints at the problems of bureaucracy which are notably solved in the movie by bravely ignoring the law.)
It’s common to hear today that the dangers of avian flu were exaggerated. I think that is a mistake. Keep in mind that H1N1 infected 15 to 30 percent of the U.S. population (including one of my sons). Fortunately, the death rate for H1N1 was much lower than feared. In contrast, H5N1 has killed more than half the people who have contracted it. Fortunately, the transmission rate for H5N1 was much lower than feared. In other words, we have been lucky not virtuous.
We are not wired to rationally prepare for small probability events, even when such events can be devastating on a world-wide scale. Contagion reminds us, visually and emotionally, that the most dangerous bird may be the black swan.