Dawn to Dusk

This page contains information about weather conditions that may help you avoid contracting Valley Fever if you live in an endemic area. If you have to be outdoors during high-risk conditions, a simple dust mask is NOT enough. Even NIOSH-approved N95 and N100 paper respirators in hardware stores, which technically could filter the arthroconidial Coccidioides spores, do not fit tightly enough around the wearer's face to provide protection. A miner's mask or other respiratory equipment with a more complete seal would be needed for true protection.

You can contract a Coccidioides infection at any time of day or night. Digging, working, or playing in soil that carries this fungus is not recommended at any time of day. It is important to note, however, that dawn, dusk, and nighttime have the least UV around, and thus the least protection, from airborne cocci. In Arizona the largest outbreaks are usually from June through July and October through November. In California, the usual outbreaks are from May through November. Valley Fever can be contracted all year round, but studies have shown that larger outbreaks tend to follow major rain and drought cycles.

The section below simply offers information and precautions but does not preclude one from living their lives normally. Please note, although the scenes below simulate the conditions in the desert, the safety precautions apply to all parts of the endemic areas, including cities and suburban communities. All it takes to contract Valley Fever is the inhalation of one spore.

This is the dawn of a new day. Notice it is windy and hazy in the desert, with dust rising into the air. The cocci spores are alive and well in their endemic areas at this time of the day. Even if you are in the city or within miles of the spores being blown around, you too can inhale the spores that cause Valley Fever. You don't have to be in the desert itself. Note: Although the dust may be mingling with airborne Coccidioides spores (called arthroconidia), remember that these spores are tiny, not visible to the naked eye, and not attached to the dust itself.

This is a beautiful, clear day. The sunlight is strong with UV and there is no wind to blow dust around. In such conditions, chances of contracting Valley Fever are reduced. However, if you are in an area where construction is going on (such as new roads, office buildings, housing, etc), working in the ground itself (gardening, playing close to the ground, crawling, etc) the danger increases. Automobiles passing by, machinery in use, or any other activity that can lift dust into the air can cause a case of Valley Fever if cocci spores are present and inhaled. Ultraviolet light is known to kill Coccidioides. However, these spores are so minute that if there is some wind they do not need to accompany a dust storm -- they might still be in the air, and you can’t count on the sun’s UV radiation to kill all the airborne spores before they can be inhaled. This means wind may be a sign to go indoors.

On a windy, hazy day, in the desert, city, or even your residence, one should take precautions. Instead of golfing or picnicking on a windy day, do indoor sports or other activities to lessen your risk of contracting Valley Fever. Avoid spending the day outdoors because the possibility of contracting a Valley Fever infection increases. It is advisable to keep your children and pets inside under these weather conditions.

A peaceful, beautiful desert sunset, without wind, can be easily enjoyed. While this is almost as safe as a still day with sunlight, care should always be taken. As noted earlier, the lack of airborne dust or wind does not guarantee that there are no Coccidioides spores nearby to be inhaled. The decreasing presence of UV also means less cocci is likely to be killed.

Notice how windy it is in our dusk picture. This is one of the most dangerous times of day, along with the complete fall of night when the wind and dust are blowing. We suggest that you avoid going outside on a windy night. Even a simple trip to the supermarket might bring cocci to your lungs when it could have been avoided. The lack of UV and presence of wind could allow cocci spores to travel hundreds of miles.

Not every inch of the endemic areas contain Coccidioides spores, but it is always wise to take precautions. Also please remember that the conditions that are unsafe for you also apply to your children and pets.