Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae (C. diphtheriae)
Spread of Diphtheria
Carriers are the common sources of infection. Their ratio is estimated at 95 carriers for every 5 clinical cases. The carriers mainly carry the organisms in their nose and are particularly dangerous. The temporary carrier state may last for about a month, but chronic carrier states may persist for a year or so.

The disease is spread mainly by droplet infection. Commonly, the portal of entry is the respiratory tract. It can also be transmitted directly to susceptible persons from infected skin lesions. The portal of entry, sometimes, may be the skin where cuts, wounds and ulcers not properly attended to may get infected with the diphtheria bacilli. Transmission by objects is possible but only for short periods of time.

As mentioned above, many sub–clinical or unapparent cases occur and immunity develops. Thus a majority of the population develops immunity.

Environmental Factors
Cases of diphtheria occur throughout the year, although winter months particularly favor its spread.

Incubation Period of Diphtheria
It’s usually about two days to a week, and occasionally even longer.

Diagnosis of Diphtheria
Diphtheria infection is a disease of children, and particularly seen in the age group one to five years of age. The infection may be acquired from exposure either to a case or a carrier. Some cases can be sub–clinical i.e. they do not have the full blown clinical manifestations. Most cases initially look like a sore throat/tonsillitis or upper respiratory tract infection. The diagnosis has to be made by conducting a thorough examination of the throat. A white colored, thin membrane at the back of the throat makes the diagnosis easier. But the disease is confirmed only after microscopic examination of a swab from the throat for the presence of the causative organisms.