Saturday, July 18, 2015

Late Night Thoughts on Pluto & Monrovia

I have been drinking a fair amount of alcohol tonight here in Monrovia, enjoying the company of some remarkable people at a dinner in the city center. We drove from there to our flat in Congo Town, about five miles away, where I sit and write this now.

The ride back along Tubman Boulevard was quiet as we listened to an extended BBC news report of the Pluto fly by of NASA's New Horizons spacecraft. I haven't actually seen many of the new pictures of Pluto given limited bandwidth here; mainly I check my email, and splurge on New York Times headlines every second or third day, but generally avoid the stories with high-resolution graphics as my internet access cuts out during the download.

Nevertheless, even listening to the radio program, it is hard not to feel a sense of wonderment at the magnificence of the event. This icy piece of rock, that circles the sun at an unimaginably long distance from our home, has become linked to us in a new and profound way; we are just a little more a part of a bigger and more amazing environment as a result of some electronic signals emanating from a piece of metal about to leave the Solar System. It is humbling. It is wonderful. It inspires awe.

Earlier today I stopped by the John F. Kennedy Hospital to check in on my resident. I didn't actually find him, but instead saw a 17 year-old who had been in terrible respiratory distress two days ago. She has an enlarged heart and had retained fluid around her lungs. I couldn't tell you the cause, though I have a few guesses--but without the resources to order the proper tests, they will remain only guesses. One of the residents--a true star, every bit as good and frankly better than many of even my high-quality residents back home--had taken the fluid off her lungs the previous two days, so that when I happened to wander in this afternoon, she had smiled for the first time I had seen her.

Her future remains tenuous, but for the moment, she thrives, and that has filled me with a certain hope, not merely for her, but somehow for Liberia, a country that has gone through much over the past year and yet moves ahead with hope and ambition. Along Tubman Boulevard, going from Congo Town to the JFK Hospital, there's a Coca-Cola billboard advertisement that wasn't there during the outbreak. It is simple. It merely shows a man, maybe my age, emerging from a car door, looking straight into the camera with a content appearance. "I'm confident of better days ahead," reads the caption.

I tend to brood, but perhaps tonight I am as well.


Friday, July 10, 2015


Thirty--that's the total number of Ebola cases in the three affected countries of Sierra Leone, Guinea, and Liberia, the latter country having been Ebola-free for months, with its first reported case on June 29th from some still entirely unknown means of transmission (the "dog hypothesis" I think is finally losing some steam since its remains tested negative, for which the dog population in Liberia is breathing one major sigh of relief).

Thirty cases--that's up from twenty last week. Hard to know, given an outbreak that is now longer than 18 months in duration, longer by far than anything previously known, whether that 20 to 30 is an uptick or just represents random statistical fluctuations at the end of the outbreak's tail. But given that the number has gone up and not down, and that we now have Liberia back in the mix (with cases not too far from where I sit typing this right now), it certainly isn't cause for celebration.

Thirty cases--a number of cases that hardly anyone except the hard-core international health junkies are paying much attention to these days. As this MSF doc laments, the news cycle moves on.

But thirty cases of Ebola is still an international emergency. Before January of 2014, the announcement of 30 cases of this disease would have dominated world headlines. This is especially true for a region the size of the current outbreak; thirty cases in a village would have gotten the world's attention only a few years ago. Now this news has to fight for coverage.

But make no mistake, as long as these cases simmer, it remains everyone's business.

Sunday, March 1, 2015

Ebola's Sword of Damocles

The mainstream American media loves a simple story, and with the West African Ebola outbreak--which is definitely not a simple story--the simple story goes like this:

Almost over!

Insert smiley face. This stands in marked contrast to the narrative from July through October, when everyone thought that Guinea, Sierra Leone, and especially Liberia might come apart at the seams. Now, however, there are confident pronouncements of Ebola's end. Ebola Treatment Units in Liberia sit almost completely vacant, and the number of cases even in Sierra Leone and Guinea is still dramatically lower than from the height of the epidemic, as can be seen here.

My quibble with such a feel-good pronouncement as I sit here in my final day in Monrovia before heading back to the States, leaving behind an unquestionably happier and healthier Liberia than the place I inhabited last October, comes from one fairly obtuse sentence in this week's WHO Situation Report. It almost sounds innocuous, a tumble of epidemiological words in the overview, a seemingly humdrum observation amidst the quiet huzzahs of fewer and fewer deaths.

This is from the first paragraph of the report, and I've emphasized the key phrases: "A total of 99 new confirmed cases of Ebola virus disease (EVD) were reported in the week to 22 February. Guinea reported 35 new confirmed cases. Cases continue to arise from unknown chains of transmission. Transmission remains widespread in Sierra Leone, with 63 new confirmed cases. A spike of 20 new confirmed cases in Bombali is linked to the previously reported cluster of cases in the Aberdeen fishing community of the capital, Freetown. There were 14 new confirmed cases in Freetown over the same period, with cases still arising from unknown chains of transmission in Freetown and elsewhere."

What that means is that, despite having an army of epidemiologists on the ground after several billion dollars of international aid has flooded the area to bring the outbreak under control, we still do not know where the virus is hiding in Sierra Leone and Guinea. This is now in marked contrast to Liberia, which not very long ago seemed the country in most dire circumstances; all current cases of Ebola in Liberia, which number only a few, have all had their chains of transmission identified. What that means is that for everyone who has developed infection, we know exactly where they got their infection from. This is not true for Sierra Leone, and it is not true for Guinea.

If you don't know the chains of transmission, then you can't do proper contact tracing. If you can't do proper contact tracing, you can't set up effective monitoring or quarantines. If you try to institute quarantines when you're shooting in the dark, you increase the chances (which are already significant) that all you're going to do is drive people who might be sick further underground, trying to outrun the quarantine and spreading the virus. This is at least partly the reason why we have seen the outbreak persist in Sierra Leone.

It's also worth noting that, while 99 new cases is a huge improvement over where we were at the height of the epidemic, by historical standards of Ebola outbreaks, 99 new cases in a week is a staggering number. The Kikwit outbreak of 1995, which lasted just under nine months and dominated news headlines for a time, had a total number of 315 cases.

I grant that the story has changed. My concern, however, is that the triumphant tone is premature. We still do not know where all of the cases are coming from. At this point, that is the news story, not the dramatic drop in cases. I find the phrase "unknown chains of transmission" almost as alarming as "Ebola outbreak" itself. We're not done just yet.


Wednesday, January 28, 2015

How Big a Deal is the Disneyland Measles Story?

In a word: big.

So far the Disneyland outbreak, as of the end of January, has tallied approximately 85 cases; about 50 of those cases have occurred in California residents. Of these, the California DPH knows the vaccination status of 34 of them. Overwhelmingly they are unvaccinated: 28 of the 34 received no vaccine, and a 29th only received one of the recommended two doses. It's generated a small amount of media splash, although the number of Americans who currently have opinions about the air pressure of footballs (including prominent physicists, for instance) vastly outnumber those who are aware of what took place at the Magic Kingdom. Many more people should know about it, however: in terms of health news, it's a big story.

But how to define "big"?

Before we get there, let's first understand some very basic facts about  measles. There are really only three concepts that are necessary to grasp measles in broad outline. First, it is incredibly contagious. Second, it is not particularly lethal. Third, there is a vaccine that is effective against it. (One should probably add a fourth: the vaccine is safe and does not cause autism.) From there, you can know what needs to be known about why this story is important.

How contagious is "incredibly contagious"? Simply put, it is either the most contagious virus known to man, or is among the top two. Epidemiologists use a variable known as R0 (pronounced "R nought") to describe a pathogen's transmissibility: the R0 tells you how many uninfected people a given person is likely to infect. Here is a graphic that compares some relative R0 values:

(Hang onto the bolded "Ebola" R0 value for a bit.)

It's important to understand that R0 is not a biologically fixed number: as the California measles data shows, the R0 for measles in unvaccinated people is much higher than it is for vaccinated people--especially since the total number of unvaccinated people at Disneyland was almost certainly much, much smaller than the total number of vaccinated people so the per capita infection rate of people who didn't have a Measles vaccination was much much higher. Measles, along with pertussis, are almost certainly the undisputed champs of microbes that cause human disease, with R0 values that range between 12 and 18. (Likewise, the R0 of Ebola has changed over the course of the epidemic, since people in West Africa changed their behaviors between June and October, dramatically decreasing the spread of the disease.)

So it's contagious--very contagious--yet it isn't especially deadly. About one or two children out of every 1000 who get measles will die. That's a small number, but isn't so small that it should simply be dismissed as a trivial threat. (Plus, some measles outbreaks have been significantly more deadly over history. Moreover, there are many more people living with compromised immune systems than ever before not only due to AIDS but also to the explosion of transplant medicine, and such patients are almost certainly at higher risk of complications from measles.)

But when you take a fairly small risk and combine it with a high transmission rate, you suddenly see large effects in aggregate. At the end of the last century, the World Health Organization surveyed measles mortality and didn't like what it saw: there were still nearly three quarters of a million people who died from measles in 2000 alone; it led to a massive worldwide vaccination campaign, such that the total mortality in 2013 was under 150,000 and the estimated number of lives saved over that time period is estimated at more than 15 million.

Which underscores, in very stark light, the third point, which is that the measles vaccine is safe and effective. A back-of-napkin calculation shows us what would happen in in the US if we took after places like rural Africa and Asia in the 1990s prior to the vaccination campaign (the 1990s being the time when anti-vaccination really began to gain traction in the West). If we could magically "de-vaccinate" every child in the US, and spread measles like wildfire--which, as noted, isn't that hard--here is what we would see: there are about 60 million kids under age 18, but let's be conservative and take the 40 million kids at greatest risk of measles and their complications, those under age 10. Measles has about a 90 percent infection rate, which means that it would be hard to avoid crossing its path. An absolute upper limit, then, would be 36 million infections, but again let's play this very conservatively and assume only half get infected. That's 20 million infections. If we take the more optimistic fatality rate of 0.1 rather than 0.2 percent, that would lead to a crisp two hundred thousand deaths. Based on the most recent available data, the actual number of deaths that occur in this age range is about six thousand.

So: measles is transmissible, it is deadly in populations even if not exceptionally dangerous to an individual, and people can dramatically reduce their risk of getting it by getting vaccinated (and, unfortunately, not going to Disneyland right now).

Another way to define the bigness of a story is to compare it to other stories. And there has been another virus that's been in the news of late. If you were unaware, there's an Ebola outbreak going on in West Africa. Ebola is, for the purposes of this discussion, a very convenient mirror image of measles: it is not especially transmissible, but it is very deadly (how deadly in the US, where there is better health care, is not fully clear). The R0 value of Ebola is generally estimated to be about two. When one thinks of Thomas Eric Duncan, the Liberian man who was infected there but developed disease in Dallas and ultimately died at Dallas Presbyterian Hospital, one sees a perfect display of this. Recall that Duncan was initially turned away from Presby and returned to his apartment, living in close quarters with his partner and five children, until he returned and was appropriately quarantined. During this time he not only exposed his family, he exposed people in the emergency room twice, he exposed laboratory personnel who didn't realize they were handling a lethal virus, and he exposed doctors and nurses. Then he exposed even more health care workers after he was correctly diagnosed. And the number of people he infected in the Dallas area after all of that was...two. Exactly the correct value, and a demonstration that it's hard to catch Ebola! (I would know!)

But when we compare the relative splash of the Disneyland story to Ebola, it's clear that there's a hugely misplaced anxiety in one area, and not quite enough understanding of how serious a story it is in another. Tallying Google searches is hardly precise science, but it does give some sort of general indicator of the level of buzz about a given topic. Obviously, Ebola is a really important story, so one can't just compare the total number of hits that a search for "Ebola" generates (~220 million) to that for the Disneyland story (~5 million). On the other hand, some searches show a much greater preoccupation with what are, in fact, minor threats to the public:

"Ebola doctor New York"--30.5 million hits
"measles"--23.4 million
"Ebola Dallas"--17.5 million
"measles Disneyland"--4.8 million
"Ebola subway New York"--3.6 million*
"risk of zombie attack"--600,000

What to take away from this? The overall Ebola story is big news, but millions of Americans are aware that Craig Spencer, the MSF physician who developed disease in New York City, took the subway and went bowling before becoming ill. In terms of risk, his subway travel and bowling adventures constituted as much a threat to the population of New York City as a zombie attack, yet this became a major source of Talmudic discussion among the chattering classes who seemed not to be aware that Spencer played everything by the book (which led to nobody being infected). The Google search on this non-story yielded only a little less than the number of hits of the Disneyland measles story.

The comparison is far from perfect, but it does I think broadly indicate the relative indifference the public has toward measles. The silver lining is that such ennui may be because most people really do have faith in vaccination and simply regard themselves as immune because of it (which is mostly true). On the other hand, this outbreak serves as an important moment to underscore what this virus is capable of doing, and just how big a lifesaver the measles vaccine really is. I don't think enough people are getting the message.


(*Searching using the Boolean operators "Ebola AND subway AND New York" yields a slightly more modest 2.7 million hits. It doesn't change the Disneyland number at all.)