Measles came to Martha’s Vineyard earlier this month. An off-island child, presumably here on vacation, was taken to the Martha’s Vineyard Hospital and diagnosed with it.

Before, measles was deep background for most of us. Now it occupies a prominent place on the psychic maps of both individuals and the community at large. A month from now, it will have shrunk considerably, but it will be a while before it seems as remote as it did in May.

Aside: For more about psychic maps, see “My Martha’s Vineyard.” Regular maps show places the way they look to a hypothetical objective observer. My psychic map shows places the way they look to me. Each person has his or her own unique psychic map. Communities have them too. Martha’s Vineyard looms very large on the psychic map of Martha’s Vineyard.

Immediately upon diagnosis, the hospital, island health officials, and the state Department of Public Health (DPH) went on red alert.

The Vineyard Gazette and the Martha’s Vineyard Times have now told us just about everything we wanted to know about measles, with all the breathless excitement that accompanies incoming blizzards and hurricanes.

Ditto social media, notably Facebook, particularly the Islanders Talk group (4,500+ members), which is where I learned what was going on.

The kid with measles visited the Airport Laundromat on Friday, June 12. I was there a week later. That was probably as close as we got.

The DPH ascertained where the child had gone when she was probably infectious but no one knew she had measles, Monday, June 8, through Wednesday, June 17. The locations included three libraries (West Tisbury, Chilmark, and Aquinnah), the Airport Laundromat, and Sharky’s Cantina and Ryan’s Family Amusements, both in Oak Bluffs. Dates and times were given for each location. Each one was notified, and they in turn did what they could to notify whoever had been there at the same time the child was.

On the subject of measles, it seems, my own psychic map was stuck in the late 1950s, which is when I had measles. As noted in a blog post earlier this month, I just turned 64. I had measles when I was 7. Measles was not a big deal then. Nearly every kid got it sooner or later. Yes, we had to stay out of school and away from the adults in the family who hadn’t had it, but it wasn’t till adulthood that I learned just how serious measles could be. The phrase “childhood diseases” made it sound like a routine rite of passage, and that’s what it pretty much was.

Not anymore. The responses, official and unofficial, to this one kid with measles took me by surprise. I caught up on some facts I’d heretofore managed to miss.

• The first measles vaccine was licensed in 1963. An improved version, licensed in 1968, is the one in use today. It’s usually combined with vaccines against mumps and rubella (known as German measles when I was a kid) in the MMR vaccine.
• Measles was declared “eliminated” in the U.S. in 2000.
• Dr. Richard Partridge, who diagnosed the case at the M.V. Hospital’s emergency room, said, “I’ve been practicing 23 years, and never seen a case of measles.” He’s based at Emerson Hospital in Concord, Mass., and does a rotation on the Vineyard and Nantucket every month.
• Measles has been making a comeback in the U.S., with 668 cases reported in 2014, the highest number since 2000. These cases came from 27 different states. (The Centers for Disease Control estimate that before the vaccine were were about three to four million cases of measles in the U.S. every year.)

Considering how infectious measles can be, the apparent fact that the 668 cases didn’t spread out of control can probably be attributed to widespread vaccination and the concept of “herd immunity.” This is somewhat complicated, but the gist is that if a certain percentage of the population is vaccinated, those who cannot be vaccinated for health reasons are protected against the disease. Because measles is “highly transmissible” — it spreads fast, and starts spreading before the telltale rash appears — the percentage required for herd immunity is estimated at 90% to 95%.

Which brings me to what were to me the most surprising facts of all:

• Martha’s Vineyard elementary schools have some of the lowest vaccination rates in Massachusetts.
• At 26.4%, the West Tisbury School’s “exemption” rate is the second highest in the state, according to a study released last year by the state DPH. That translates to about 75 un- or under-vaccinated kids. The exemption rates at the Chilmark School and the charter school, both too small to be included in the state study, are similar.
• Exemptions can be granted for medical or religious reasons. Medical exemptions must be approved by a doctor and renewed every year. Religious exemptions don’t have to be approved by anybody and are good for life.
• The state average for religious exemptions is 1%, but for the seven schools surveyed in Dukes County the religious exemption rate is 18%. Most of the exemptions in West Tisbury are for religious reasons.

This is curious. Yes, there are religions that frown upon or proscribe medical intervention, but they are not widely practiced in West Tisbury. I suspect that the religious exemption is serving as a “don’t ask, don’t tell” loophole for parents who for whatever non-medical reason don’t want their children vaccinated.

Yes, I’m aware of the roiling controversy about vaccinations in general, but no, I’m not going to go there. What intrigues me about all this is how we as individuals and as a community assess risk and decide what to do about it. For instance —

• Vaccinations carry some risk. They don’t work for everybody, and for some they may do harm.
• As long as measles remains a remote hypothetical possibility, the risks associated with vaccination loom large and larger. Once measles appears on the psychic map, those risks seem manageable.
• Parents who consider vaccines unsafe don’t think twice about putting their kids in the car and driving down-island, up-island, or off-island.
• As long as measles remains a remote hypothetical possibility, those who are vaccinated or otherwise immune don’t think much about those who aren’t. “It’s their right, it’s a free country,” etc., etc., etc. Once measles appears on the psychic map, live-and-let-live goes — not quite out the window, but it’s headed in that direction.

In other words, it’s much easier to tolerate something that poses only a remote, hypothetical threat.

At the same time, somewhat paradoxically, the more familiar, worthwhile, and/or unavoidable something is, the better able we are to deal with the very real risks. This freakout about measles would have been unimaginable when I was a kid.

So if a reasonably safe, highly effective inoculation against Lyme disease — which isn’t spread person-to-person but is widespread on Martha’s Vineyard — became available, would those who oppose vaccinations in general make use of it?

Some supporting info:

Centers for Disease Control FAQs on measles

“Low Vaccination Rate Prevalent on Island,” by Alex Elvin, Vineyard Gazette, February 12, 2015

“Measles Diagnosis Exposes Martha’s Vineyard’s Vulnerability,” by Barry Stringfellow, Martha’s Vineyard Times, June 25, 2015 (posted June 24)