I'm assuming here that you already know what the curveball feature is like: they'll start appearing in campaign mode shortly after a map is entered and will provide various beneficial or harmful effects, most of which will be temporary. The effects of a specific curveball can vary: e.g. during the Bullet Benefactor, the extra drops may be ammo, they can be explosives or they can be weapons. Zombies that have been altered by the curveball can be spotted by their eyes that glow blue. Completing curveball objectives will reward either influence or prestige, which can be used to buy Daybreak items from the prestige trader. Rule of thumb seems to be that you get rewarded prestige for combat missions and influence for others. Check the wiki [state-of-decay-2.fandom.com]for a detailed list of known effects.

When you have played for a while, you'll notice that sometimes curveballs produce threats that need a response and sometimes they provide temporary opportunities that can be made use of. Sometimes it seems unclear if the effects are worth the attention. Your community can benefit a great deal if you know how to exploit the opportunities and tackle the risks. Below, I'll go through the list of curveballs and comment on what kinds or risks and opportunities they come with. I'll also explain some details about how the curveballs work, since some of the effects are not obvious or fully explained in-game.

Avoid the area during these:

Elevated Senses, Strange Mutations, Explosive Gunk Zombies, Sentinel Mutation (zeds have increased eyesight, impaired hearing; there is also a reverse mutation to this): these are all curveballs where zombie behavior has changed within an area in a way that generally makes things harder. The Sentinel mutation and its reverse also come with a positive effect that could be exploited, but I find both of them tend to be more trouble than good.

Elevated Senses is an especially dangerous curveball since you tend to get swarmed even within safe zones, including your own base.


Respond quickly to these:

The Black Heart, A Broken Heart, Fuelling the Plague, Out for Blood: these are curveballs related to a specific plague heart on the map. The problem is that the curveball will wake up the plague heart, which will then start spewing out infestation hordes. This can be a problem, especially if the plague heart in question is part of a cluster, so that destroying it will wake up one or several others. Like any awakened plague heart, it's usually best to prioritize taking it out first.

The Black Plague Heart is the worst curveball to have. It makes the area much more dangerous and the plague heart itself many times more durable. A couple of surprises I've come across are that the area can drain fuel even if that effect is not listed on the curveball page and that zombies that have changed into a tougher form are also resistant to fire. This is the time to use whatever good stuff you have been saving up, like scentblock and smoke grenades.

Ransacked Outpost, Lone Raider: a hostile enclave shows up and disturbs the income of some of your resources. Unlike Outlaws Passing Through, these won't end on their own. The quality of their weapons seems to be better as well.


Negative effects but can be removed:

Radio Silence, Under the Weather, Missing a Few Bolts, Highly Combustible, Outlaws Passing Through, Gargantua Mutation: these will all end on their own after a while but can be removed by completing an objective.

Radio Silence can be tricky because the condition to remove it is to secure a radio tower. If you are out of luck, it can be in a red zone, which means you'll have to remove one or several plague hearts first.

Unsurprisingly, the juggs during Gargantua Mutation will be tougher than usual, so pick up a few more rounds of 50 cal.


Temporary negative effects:

High Toxicity Bloaters, Vicious Rumours, Thick Skinned, Bangernomics, Smoke Storm: there is no objective for removing any of these. They'll make life harder for a while but will disappear on their own afterwards.

High Toxicity Bloaters makes driving especially dangerous. Consider using the Primary Care facility action to boost your infection resistanve when this is active.

It's best not to do any especially difficult missions when these are active, if you can avoid it.


Temporary boost to survivors:

Up and At 'Em: on the other hand, the positive temporary boost, Up and At 'Em, gives you a period when your survivors are especially strong. This would, in principle, be a good time to take on especially challenging jobs, though the effects are not so powerful that they'd really make a big difference. The effects will also only last for a fairly short time, so you may be busy doing something more urgent.


Temporary looting opportunities:

The Bullet Benefactor: this one is my favorite. You can get a supply crate with good quality loot: the weapon drop variant can include at least Spec Ops Vectors and high quality sidearms. Weapons from looting have included Custom AKs and Spec Ops AWs. I think you can get extra weapons from loot even if it's not the weapon drop variant.

Just Fed, The Lost Platoon, Juiced Up: you might try to use these for farming. The problem is that during these events, zeds drop a variety of different items in fairly small quantities. You tend to end up with small stacks of many different items that will fill up your inventory. Soldier zeds during Lost Platoon won't drop weapons: it's mostly modest amounts of random ammo and healing items. There are explosives too, but mostly not the high quality kind. During Juiced Up, zeds drop mostly luxury items and sometimes ethanol. Loot during Just Fed seems to be consumables, including healing items.

High temperature Zombies and Cesspit Zombies can be used to farm plague samples and influence, respectively, but I don't find them all that useful.

Bait Crate: the crate will still be there after the event ends (though it will probably disappear after a reload). During the event you could exploit the effect by looting the area while zombies are distracted by the crate.


Other temporary opportunities:

A Well Oiled Machine: costs for many facility actions are drastically reduced. This is a great time to sort ammo and produce gas cans. Sorting ammo is especially useful during this curveball: on Lethal, the cost is reduced to one third.

Finer Things in Life, News Travels: the most important thing about these are the improvements to selling and buying. This is the right time to sell your luxury items and anything else you won't use or strip for parts. IIRC Finer Things in Life can give you double selling prizes for luxury items.

Dulled Senses and Soft Skins make it a lot easier to deal with zombies within their area of effect. If there are plague hearts in there, this is the time to take them out.


Other

Zombie Burnout: neither especially good nor bad

Scavenger Hunt: Provides a trickle of minor loot. The increased threat only matters if there are awake plague hearts on the map.

Influx of Meds: provides a trickle of meds, and you can find more stimulants. I don't know if the effects vary, but this one doesn't seem to have a downside similar to Scavenger Hunt.