Guys, this is a really simple problem that, I admit, the manual lacks details on -- though there is *some* information. But, if you have played the game and observed, its easy to figure out what's going on.
Basically, in a malaria zone, you will lose more men than replacements will replace. On average, you will lose about one Aviation Support squad in a base force every 2-3 days. If the Base Force (BF) is in a malaria zone AND is in a hex that does NOT have enough ground support, you can figure on losing an Aviation Support Squad about every day. It gets worse if the hex also does not have enough supplies.
The key is : don't think of a set of one or even two base forces as capable of keeping a base up at optimal (for what you are trying to do) for that base. If you want to keep a base at a certain level of aviation support, best to have some base forces back in a non-malaria zone and well supported, a central location where all base forces can go to rest and recuperate.
Here is what I do : I make sure I have one base in a non-malaria zone that has more than enough regular support, and a good starting airbase size. (note : lack of regular support will also cause attrition to all forces at the base lacking support). I mentally designate this spot (usually T'ville for the Allies), as the place where I will dump all my base forces when I get them as reinforcements, and where I will pull them when they've gotton depleted on the front line. On average, up to half of my Base Forces are back in either Noumea or T'ville, rebuilding. But, the ones on the front line are almost always at 85+% strength. If they were all on the front line, due to attrition, I'd actually have less available.
Stick with me here : usually, as an allied player, you want to keep PM up above 250 aviation support. So, what do you do? You get a couple of base forces up there that total 250+. After a month or so, they are worn down and you might be in danger of dropping below the key 250 level. What do you do? Oh My! You transport in 2 more base forces from your pool, and pull the two worn down ones out. The worn down ones will rebuild at about the same rate they lost squads, so by the time the new guys have gotton wasted from malaria, the old BFs will be back up to snuff.
A quick way to do all this BF shuffling is with air transport. I routinely move two Dakota groups to the hex that I want to pull the BF from, and I have 3 or more Dakota groups in T'ville, which can air transport the new squads in. Do this simultaneously, and it gets pretty seamless.
Here is an added bonus if you are allied for this strategy : Radar. Most of your base forces do not start with Radar. However, if you keep them in a non-malaria zone and let them build up to full strength, they just might get one or two radar squads. You do get radar squads as replacements, and they can theoretically get added to any squad. Air combat in a hex with radar benefits the side that has the radar. Watch the Japs shy away from air combat in PM now that your old but new again squads now have radar added. The only negative to a BF that now has radar is that you can't move the radar by air, you must load them on to sea transports. So, its actually a good idea to have a mix of non-radar and radar BFs. The non-radar ones can move quickly with Dakotas, the radar ones become a more permanent move. Usually, the malaria will kill off the radar squads, but not always.
If you have been following this strategy, at certain points of the game, you can go "offensive" and put all of your BFs up front, giving all your bases maximum 250+ support. The allies can do this because they have a lot more planes and airgroups. Prepare for it. Build up supplies first at the bases you are going to do this at, so that your bombers will fly when you make the offensive move. In the space of two days, you should be able to get most of your BFs up front, and pile on the aircraft at those bases. The enemy will be mightily suprised by the appearance of 150 fighters at a base that was previously only putting up 24.
Last time I checked, the forums were messed up. ;)