Quick-and-Dirty Estimate of Number of nCoV2019 Infections in Wuhan

This post concerns the very rapidly developing story of the new corona virus (nCoV2019) outbreak in Wuhan, China.

Let me begin by saying I’m neither an epidemiologist nor a public-health expert. Here are a few of the people I follow on Twitter who have way more expertise than me in these areas:  @HelenBranswell @neil_ferguson @nextstrain @mlipsitch

However, I think about populations and parameter estimation a fair bit in my work on microbial population dynamics.  I wondered about the implications of the fact that there are already 5 cases of travelers from Wuhan into the US who have tested positive for this virus.  That fact made me think there must be quite a large number of infected people (including, thankfully, many for whom the infections are not severe) in Wuhan.

So here’s a quick-and-dirty, rough-and-imprecise, laden-with-assumptions estimate that I obtained for the number of infected people in Wuhan.

a)  China has ~1.4 billion people, and Wuhan has ~11 million, so the latter makes up ~0.8% of the Chinese population.

b)  In recent years, ~3 million Chinese travelers have visited the US per year. Naively extrapolating from the above, that would imply ~24,000 from Wuhan per year, or ~500 per week.

c) In the past week or so, 5 travelers from Wuhan to the US have been found to be infected with nCoV2019. Naively extrapolating again, that suggests an infection rate of 5/500 = 1.0% of the Wuhan population, or ~110,000 infections in that population.

d) Interestingly, this falls right in the middle of another estimate (performed very differently, I presume) from @neil_ferguson (Imperial College) who suggested a possible range of 30,000 to 200,000.

e) There are many large uncertainties associated with my crude estimate. Here are just a few of them:

  • The small number of US cases introduces great uncertainty, in terms of sampling uncertainty alone.
  • Given the on-going spread of the virus, and the fact that these travelers might have visited Wuhan a week ago, this estimate would be outdated and a current estimate would be higher.
  • Travel is not uniform seasonally (and this outbreak corresponds with holiday periods on both ends). I also understand that Wuhan has many universities, and there may well be a disproportionate number of travelers from Wuhan at this time of year. This would imply fewer infections in Wuhan to produce 5 cases here.

I welcome any comments, corrections, and criticisms.

NEW INFO 1:20 pm (Jan 27):   Here’s another interesting (and concerning) bit of data from the CDC. So far, 37 cases have been investigated.  Of these, 5 have been positive, and 32 negative. However, there are 73 more cases with pending test results in just this first week of CDC data. If the % positive holds in these pending cases, that would triple my estimate of proportion & number infected.  That is, the product (5/37) x 73 suggests that an additional 10 or so infected individuals will be identified as having entered the US in this first week. Again, this is a crude estimate with assumptions, and these potential cases are also presumably in isolation, etc.

NEW INFO 2:00 pm (Jan 27):  On Twitter @afferent_input found monthly data on visitors to US from China. Seasonal data suggest number of travelers in this period might be ~2X higher than my crude estimate, which would reduce the inferred infection proportion and numbers relative to my initial estimates. This factor and the other new info posted immediately above might roughly cancel. Again, all of this information is rough and crudely extrapolated. And none of it bears on critical issues of distribution of severity of infections, etc.

 

 

 

 

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Revisiting Telliamed

I started this blog, Telliamed Revisited, back in August of 2013, after attending a conference at which a colleague emphasized the value of social media in science.

I recall being questioned on Twitter by someone who expressed skepticism whether my blog would last or quickly be dropped. (Hey, I had already been running the LTEE for a quarter of a century at that point, so you’d think I’d get a little slack.) Anyhow, I said I didn’t really know, and that this blog was a personal experiment in communication.  In any case, I’ve now kept it up for six years, but with only occasional posts … about 100 in total so far.

If you want to follow a regular blog that is focused on science and related issues, I highly recommend Dynamic Ecology.  Jeremy Fox, Meg Duffy, and Brian McGill discuss interesting issues multiple times almost every week.  Impressive!

Anyhow, reflecting on my blog experiment as we head into a new decade, I was interested to see which of my posts had been viewed most often.  Here are the top 10:

Here are five more that are among my own favorites, but which didn’t make the top 10:

Also, if you’re wondering about the name of this blog, see the following post:

Last but not least, Happy New Year—and New Decade—to one and all!

Telliamed

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That Didn’t Last Long

My previous post did not age well.  After a gorgeous start, Autumn has come to a bitter end here in East Lansing—many weeks before the official start of Winter.

We had several inches of snow two nights ago, followed by extreme cold last night.

It is quite beautiful, though, as you can see in the first picture below.  But many of the local sidewalks are a hazardous mess—ice interspersed with rock-hard lumps of snow—and the snow-covered lawns are now getting covered with leaves that hadn’t yet fallen, as you can see in the second picture.

Snow in November 2019

Leaves on top of early snow

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Autumn at MSU

A lovely autumn morning in East Lansing.

Maple MSU Oct 2019Red Cedar foliage Oct 2019

Next week I’ ll get to discuss a couple of my all-time favorite papers – Chao and Levin on colicins, and Lieberman et al. on parallel evolution in an epidemiological setting – with graduate students in our Integrative Microbial Biology course.

That is all.  Happy Friday, and have a great weekend.

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Hat Trick

This past weekend Madeleine and I attended the annual meeting of the American Academy of Arts & Sciences in Cambridge, Massachusetts. The Academy was founded in 1780 by John Adams and several dozen other scholar-patriots “to cultivate every art and science which may tend to advance the interest, honor, dignity, and happiness of a free, independent, and virtuous people.”

It was an especially exciting meeting for us because we got to see three of our dear friends inducted as new members:  Paul Turner and, as International Honorary Members, Valeria Souza and Sebastian Bonhoeffer.  All three of them signed the membership book, putting their “John Hancocks” alongside those of distinguished artists, scientists, scholars, and leaders (including the John Hancock) from the past 239 years, while Madeleine and I celebrated with their spouses and families.

I’ve known Paul, Valeria, and Sebastian for decades.  Paul was a graduate student in my group at UC-Irvine, and then he moved with me to MSU, receiving his PhD in 1995. For his dissertation, Paul studied issues related to vertical and horizontal transmission in bacteria, including the roles of density- and frequency-dependent selection. Paul is a professor at Yale University, where he and his team study the evolution and ecology of viruses, including some that can specifically target antibiotic-resistant bacteria and have been used to cure life-threatening infections.

Valeria was a postdoc in my group, also first at UCI and then again at MSU. She worked with Paul on a fascinating, but challenging, experiment to investigate the effects of horizontal gene transfer on the speed of adaptive evolution in bacteria. Valeria is a professor at Universidad Nacional Autonoma de Mexico, where she and her group conduct research and work with the local community, governmental agencies, and nonprofits to conserve the Cuatro Cienegas basin, a biologically unique and fragile system of oases in the Chihuahuan Desert.

Sebastian and I met at Oxford University in 1993, where he was a graduate student and I was on sabbatical. We collaborated on a theory project that examined the hypothesis that pathogens with long-lived propagules would evolve to be more virulent. More recently we’ve taught together in the Guarda (Switzerland) summer course on evolutionary biology. Sebastian is a professor at ETH Zurich, where he and his team construct and analyze mathematical models of population dynamics to understand, for example, the pathogenesis and spread of HIV and other viruses.

Besides being creative and talented scientists, Paul, Valeria, and Sebastian are three of the nicest people around. I’ve been incredibly fortunate not only to work with them, but also to know them as close friends.

And there were so many other outstanding inductees, some of whom I’ve also known for many years including microbial ecologist Jo Handelsman (University of Wisconsin), theoretical ecologist Mercedes Pascual (University of Chicago), evolutionary biologist Mark Rausher (Duke University), plant biologist Detlef Weigel (MPI Tubingen), and evolutionary biologist Kelly Zamudio (Cornell University).

Each of the 5 “classes” had a speaker give a short talk to all the inductees and their families. Representing the Biological Sciences, Jo Handelsman gave an impassioned talk “On the importance of soil.” It’s something almost everyone takes for granted, and yet fertile topsoil is incredibly valuable, it’s disappearing in many areas, but it can be preserved and even enhanced with improved agricultural practices. Representing Public Affairs, Business, and Administration, Sherrilyn Ifill (NAACP Legal Defense Fund) gave a clarion call to fix American democracy.

The evening before the induction ceremony there were artistic performances and presentations by several new members including jazz pianist, composer, and singer Patricia Barber.  The morning after the induction included a performance by, and discussion with, the incredible playwright, filmmaker, and actress Anna Deavere Smith, who performed and described how she constructs her amazing one-woman shows.

Throughout all the events, the staff of the American Academy of Arts & Sciences were superbly organized and warmly welcoming.

[Paul Turner’s family in the theater just before he signs his name into the book of members of the American Academy of Arts & Sciences]

Paul's family at AAAS 2019

[Valeria Souza signing the book, with Paul Turner just behind her and waiting his turn]

Valeria signing, Paul just behind, AAA&S 2019

[With Valeria Souza and her family following the induction ceremony]

Valeria and family at AAAS 2019

[Sebastian Bonhoeffer and his wife Hanna (next to me) with Madeleine (next to Sebastian) and me the evening before the induction ceremony]

bonhoeffers-and-lenski-aaas-2019.jpg

[Yours truly along with Mercedes Pascual, Paul Turner, and Sebastian Bonhoeffer]

AAAS 2019 Mercedes, Paul, Sebastian and me

[Sebastian, Paul, Valeria, me, and Luis Eguiarte (Valeria’s husband, and also a superb evolutionary plant biologist]

Sebastian, Paul, Valeria, me, Luis AAA&S 2019

[Paul and I compare our biologically themed ties.]

Paul and me at AAA&S 2019

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Freezer Burn

One of the more challenging aspects of running a microbiology lab, in my opinion, is freezer management.  There’s a lot to keep track of, both in terms of quantity and quality.  My lab team and I take great pride in the quality control of our work that has allowed us, for example, to keep the LTEE running for over 30 years and 70,000 generations without contamination.  Or rather, as I’ve posted before, we’ve had occasional accidents including cross-contamination of the replicate lines, but we’ve caught those mistakes and, using frozen samples, restarted as needed to keep things going smoothly and cleanly.

With my lab group now running for ~34 years (I started at UCI in 1985), and with so many hard-working students and postdocs, we’ve filled up lots of –80C freezers.  And that’s despite shipping many strains to scientific collaborators and former lab members who’ve continued to work on the various projects—the LTEE is only one (albeit the longest) of the many projects we’ve done in my lab.  Adding to the storage challenge, we’ve got duplicates of most samples in case we have a problem with the primary sample (say, someone drops a vial on the floor).  Also, to avoid compromising our primary or backup samples, I ask that everyone who plans to use any sample (usually a set of many samples) more than once make his or her own working copies of the samples.

And freezers sometimes fail, despite our best efforts to maintain them in tip-top shape.  So over the years, I’ve always tried to keep a freezer’s worth of spare capacity across our multiple freezers, so when one fails, everything can be moved into a functioning freezer.

On Sunday, one of our workhorse freezers failed. Most of our freezers have alarms that send out an email alert to members of the lab that something is amiss.  This one did not (oops!), but fortunately undergraduate Jessica Baxter (working hard even on the weekend), noticed that it had “warmed up” to –40C or so.  I was off visiting grandkids, but Jessica was able to reach Devin Lake, who manages the lab’s operations extremely well, even as he does double-duty as a grad student.  Devin and Jessica were able to find enough spare capacity to get everything into one of the surviving freezers, so nothing was lost.

But that meant we had no more spare capacity.  We can buy a new freezer, although my experience (and hearing about many other failures) is that they don’t make them like they used to.  And what if another freezer were to fail before we got a new one?

I knew we had many freezer racks full of now-unimportant samples—working copies made by people who’ve left the lab, as well as samples from abandoned experiments and various long-ago projects that won’t be revisited.  So I asked Devin to look through the freezers for the identifiers on various racks (besides the LTEE and any associated with current lab members) that would give me ideas of what we could discard to free up some space that we will need for ongoing projects … as well as the possibility of another freezer failure.  (But please not that!  I’m not trying to tempt fate—I just want to be prepared.)  It turns out there were lots of possibilities, so Devin and I spent a couple of hours checking boxes and then removing about 20 freezer racks, most holding 6 to 10 boxes, and most of those with dozens of small vials, each holding many millions or even billions of bacterial cells.  Seeing the names of former lab members on the boxes, and the numbers on all those vials, was a humbling reminder of all the hard work that so many have done over the years.  Devin carted three loads of discards down to one of our workrooms, where hardworking tech John Baltusis emptied each box and prepared the vials for the sterilization (autoclaving at high temperature) that’s required before they can be discarded.

Thanks to the hard work of Jessica, Devin, and John, the lab avoided any setback. In fact, our freezer collection is now a little more manageable than it was before.

[Devin Lake, in front, with one of three cartloads of samples to discard, while John Baltusis removes the samples from one box before autoclaving.]

Devin, John, and freezer mess

 

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Half Life

Today marks a unique day for the LTEE and me.

The LTEE started on February 17, 1988.  That was 11,517 days ago.

I was born on August 13, 1956.  That was 23,034 days ago.

That means that the LTEE is now half as old as I am.

To put it another way, I’ve spent half a lifetime on the LTEE.

Well, that’s not quite the right way to put it, since I’ve done a few other things during that time. Like raising a family—with a lot of help.  And a lot of other science, also with a lot of help, not to mention all the work of so many students and collaborators on the LTEE itself.

And unlike a radioactive isotope, the bacteria haven’t been decaying—they’ve been getting better and better at living in their flask-worlds.

My hope is that this long-term evolution experiment will continue for a long time. A very long time. For a lot longer than my own lifetime.

Here are a couple of photos from around the time the LTEE started. The first one shows Madeleine and me camping near Joshua Tree National Park in the summer of 1987, at the annual retreat of the UC-Irvine EEB department, and only a couple months before the birth of our youngest. The next one shows me snuggling with my three kids in early 1989.

june-1987-desert-x-with-mjan-1989-with-3-kiddos

How time flies. Luckily, though, I get to snuggle with my three grandkids now.

Bacterial generations. Human generations. Growing, evolving, and learning.

 

 

 

 

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