*Corresponding author: Dr. Sayan Bhattacharyya, Associate Professor, Microbiology, AIIH&PH, Kolkata, India
How to cite this article: Sayan Bhattacharyya and Akash Dasgupta. Fungi Causing Sinusitis and Otitis: Are the Air, Temperature and Relative Humidity to Blame?. Glob J Oto, 2023; 25 (4): 556170. DOI: 10.19080/GJO.2023.25.556170
Fungi in air are notorious for causing allergic and invasive sinusitis. Especially fungi of the genera Aspergillus and Rhizopus are known for this. Yeasts in air can also cause sinusitis. Sometimes there is variation in load of these fungi with relevance to ambient temperature, relative humidity and temperature. These things are very important from public health viewpoint.
Fungi in air can be allergic or invasive. They may irritate the nasal mucosa in man and produce allergic rhinosinusitis, fungal ball or saprophytic sinusitis . Others classify fungal sinusitis as invasive and non-invasive. There are three subtypes of non-invasive fungal sinusitis (FS): Fungal ball (FB), saprophytic fungal sinusitis (SFS), and allergic fungal rhinosinusitis (AFRS). Similarly, there are three subgroups of invasive fungal sinusitis (IFS), namely acute invasive rhinosinusitis (AIRS), chronic invasive rhinosinusitis (CIRS), and granulomatous invasive sinusitis (GIFS) .
Fungi get disseminated in air continuously. For example, from buildings under construction, molds spread in air and can be inhaled. This spread can be enhanced by dampness. In fact, damp indoor spaces have been linked with health problems like bronchitis, asthma, cough, wheeze, and shortness of breath .
Several studies have quoted that Aspergillus spp. in outdoor air are more common in urban than rural settings in the province of Madrid. Hence this problem of mold in air is more common in victims as compared to villages . Leaky roofs and leaky pipes can lead to spread of these fungi in air, causing infections like allergic fungal sinusitis or hay fever, and hypersensitivity pneumonitis . Exposure to household molds have also been linked with early onset otitis media . Especially, high levels of ‘other’ mould (defined as total spore count minus counts for Penicillium, Cladosporium, and yeast) have been associated with early otitis media.
Yeasts in air can also cause sinusitis. However, they are rare causes of invasive paranasal sinusitis. Among yeasts, Candida albicans and C. tropicalis are relatively commoner causes of sinusitis, followed by C. kefyr which is rarest . So otorhinolaryngologists may come in the picture for surgical treatment also. Otitis can be seen along with paranasal sinusitis.
Ambient temperature has a role to play in the burden of mold in air. Molds are found later in the day with an optimum temperature of 25 to 29°C. Increased use of air conditioners and air coolers to reduce room temperatures in summers also lead to increased circulation of molds, especially if these machines are not regularly serviced .
Increase in relative humidity above 45 percent has been associated with increased level of fungal molds in indoor air in a study done in Canadian homes . Another study in Iran has found positive correlation between number of fungi in outdoor air and relative humidity in spring and autumn seasons . Urban slums in India, with their ever increasing population in newer cities, might
be highly hazardous for the residents owing to damp dwellings
along with high household crowding index.
Different patterns of diurnal variation have been observed for
spores of different fungal species in ambient air. A study in Kolkata
found Ganoderma, Nigrospora, Ascospores, and Basidiospores
to have night peak patterns between 6PM and 5AM. Periconia, Fusarium
and rust spores were found to have post-dawn peak patterns
between 5AM and 10AM. Bispora (at forenoon), Curvularia
(at noon) and Cladosporium (at afternoon) were found to have
midday peak patterns between 10am and 6pm. Aspergillus spp.,
Penicillium spp. and Trichosporon spp. were found to have double
peak patterns . However other environmental factors like
temperature, relative humidity, wind speed might have an influence
on these diurnal variations and may vary from place to place
depending on weather patterns.
A year-long study conducted in South India found A. fumigatus,
C. cladosporioides, and A. alternata, throughout the year in
ambient atmospheric aerosols. C. cladosporioides was the most
abundant allergenic fungus present in the region. A. fumigatus and
C. cladosporioides had higher concentrations during monsoon and
summer, whereas in winters, A. alternata had higher concentrations
. Another study in industrial township of Barrackpore,
West Bengal revealed temporal variation in ambient fungal spore
load. Highest concentration was observed during the post-monsoon
period and while it was lowest during winter. Most of the
observed fungi (65%) are from ascospore, basidiospore, Periconia
and Aspergillus spp. and Penicillium species. Wind speed, Dew
point, PM2.5 concentration and NO2 levels were found to be important
predictor variables in determining atmospheric fungal
A study in Kolkata over a 2-year period found Alternaria, Aspergilli,
Penicilli, Bispora, Drechslera (Bipolaris spp.), Cladosporium,
Nigrospora, Ganoderma, Pithomyces, unidentified ascospores
and basidiospores as the major fungal agents in ambient air. August
was found to be the most spore-rich month with lower concentrations
in late winter in January, February, least in March. Bispora,
Ascospores and Basidiospores were high in monsoon months
whereas Nigrospora were present throughout the year. Significant
positive association was found between relative humidity and total
aeromycota. Skin prick tests performed on patients using 20
different fungal extracts found maximum sensitization to Aspergillus
Our own experience shows that aseptate hyphal mods like
Rhizomucor spp. grow well in air over a relative humidity of 50%
and temperature of 29.5°C. It maybe so that more humidity favors
mold growth and dissemination in closed spaces. Aspergillus niger
was seen mostly if relative humidity exceeded 86%, but also found
in a humidity as low as 45%. Aspergillus fumigatus was seen in
indoor air in temperature as low as 22°C.
Settle plate method or active air sampling can be done to retrieve
these fungi in air. In settle plate the plate has to be kept
open in the area for about 1 to 2 hours and then placed in incubator
for 1 to 2 days. Active air sampling takes lesser time but is
costlier. We are using passive sampling by Settle plate method using
Sabouraud’s Dextrose agar for this purpose. Variation of flora
with respect to temperature, time and relative humidity can be
assessed by an instrument called Digital Hygrometer which is easily
available commercially (Figure 1).
Thus, Otorhinolaryngologists may be consulted for ear and
nasal sinus infections caused by these fungi in air. These fungi can
cause both allergic and invasive infections. There is significant
variation also in these airborne fungi, particularly with respect to
temperature and relative humidity. More molds are seen indirectly
with increasing relative humidity, particularly in the range of
45%-65%. This dissemination increases more if construction and
repair works are happening in buildings, facilitating the dissemination
of conidia and spores of fungi and resultant allergic and invasive
fungal infections in man and otomycosis. These things need to be studied and explored more and can be termed emerging topics encompassing Microbiology, occupational health as well as