One of the reasons humans kept improving on civilization is it made us healthier. We enjoyed not enduring scourges like cholera and typhoid.

We stopped throwing our excrement on the streets and started filtering water and taking baths more often.

Sometimes we get complacent. We forget about basic sanitation. Or we let infrastructure rot, like in Flint, Mich.

Biology has a way of waking us up when that happens.

It certainly woke San Diego up.

We have always had homeless neighbors. But something happened about seven years ago. They pitched tents – set up encampments. They formed a disjointed neighborhood of their own, transcendent of our official neighborhood boundaries.

It made sense that the Occupy movement that clustered tents outside City Hall attracted homeless people too. The movement toward community picked up pace.

Even as the economy kept recovering, the encampments were attractive. People relied on and protected one another. Most of all, they seemed to make a decision to stop hiding – quite the opposite, they were announcing themselves.

They were no longer just lying on the streets. They were living on the streets.

The tents were a blazing bonfire – an SOS from refugees right next door. We’ve covered it for years, but it never registered as a city emergency. It was just this festering problem we could keep managing.

Last year, exasperated, we assigned Lisa Halverstadt to work with photojournalist Jamie Scott Lytle to capture the tent cities in East Village and implored that people “Look at Your Tent Cities, San Diego.”

Look at them! They made it impossible not to see, but we still didn’t look.

Meanwhile, the tent cities grew. As much as they might have provided community and more safety, they were dangerous, filthy places. Disease, misery and addiction haunted them.

San Diego’s elite, as genuinely concerned as they were, had no idea what to do. No leader made any sense out of it. There were numbers and esoteric debates of enormous complexity. Every year offered big, vague policy promises.

And still it festered.

Local media, out of ideas on how to get attention to it, even did something unprecedented. Most all major local news organizations united to cover one thing, one thing only, for one day: homelessness.

Officials hired high-profile people to tackle the problem. Initiatives were set. But the tent cities kept going. There were feeble attempts to disrupt them. But nothing changed.

Finally, nature woke us up.

Nature doesn’t have patience for our political debates. Hepatitis A is a living thing, just like us. It found the right conditions and reproduced rapidly. It jumped from host to host. Through their feces.

We don’t have adequate public bathrooms in San Diego. Again, we knew this!

We pretended like downtown was going to be a walkable, urban destination and yet we didn’t give it bathrooms. We actually took out bathrooms rather than add them. We locked the ones we put in.

Why? They are so sparse, people congregate around the ones that open.

What did we think these homeless people would do? Where did we think their poop was going?

I would run into callous people all the time who would say things like, “Homeless people are just lazy and there’s nothing we can do about it.” Stop saying that. Be as heartless as you want. But stop saying that. We are a modern civilization. We know how to build cities that don’t have fecally contaminated streets.

If we don’t make sure everyone has access to shelter and sanitation, we will pay the price.

Yet still the mayor, City Council and county supervisors presided for three years over the expansion of a Skid Row. Nothing changed until a disease that spreads via feces started getting a lot of people sick.

And even then, nothing changed until media pointed out that a poop-borne disease was spreading rapidly and city and county government didn’t seem to be addressing it with urgency or sounding the necessary alarm.

Now we have action. But of course, it’s mixed with blame.

The county and city are locked in a quiet battle to prove who was more at fault. Let me help them resolve it:

The county should have alerted people better about what was happening. And the city should have had better leadership to do something about the tent cities and helpless misery in our streets.

Congratulations, you both win. You have risked the city’s image as badly as anything the “Enron by the Sea” contemporaries wrought.

Now the city is clearing the streets. The homeless people aren’t vanishing, they’re spreading out. The mayor and county now want them to set up camp in a parking lot until big tents are built. But the parking lot tent city and the coming mega tents will only hold a fraction of them. Many of the people who go there might have been hidden in canyons or barely getting by from shelter to shelter.

There is no plan for where the rest will go or where the people will live. Nobody can tell us what the “temporary bridge structures” – that’s how officials have described the tents – are a bridge to.

But the action and urgency is a welcome start.

It’s just too bad it took an awful virus – a wake-up call from nature – to get us there.