Module 4: Healthcare practices for common contagious infectious diseases

Feline Respiratory Pathogens and Their Properties


  • Feline herpesvirus (FHV)
  • Feline calicivirus (FCV)


  • Bordetella bronchiseptica (Bordetella)
  • Chlamydia felis (Chlamydia)
  • Streptococcus zooepidemicus (Strep zoo)
  • Mycoplasma felis (M. felis)

Incubation Period

The incubation period for the known bacterial and viral respiratory pathogens is ≤1 week. This short incubation period contributes to a rapid increase in the number of sick cats within a short period of time. Preclinical shedding occurs during the incubation period, meaning infected cats are contagious before appearance of clinical signs.

Shedding Period

Most cats shed FHV and FCV in ocular, nasal, and oral secretions for <1 month. However, up to 50% of FCV-infected cats can shed the virus for 3 months. FHV infection is life-long: stress reactivates viral replication, resulting in short-term shedding. FCV can establish persistent infection in some cats with intermittent virus shedding.

Bordetella, Chlamydia, Mycoplasma felis, and Strep zoo may be shed for weeks to months if infected cats are not treated with appropriate antibiotics.

Here is a summary table of the Feline URI pathogen incubation and shedding periods. This is included in the Feline Respiratory Infections in Shelters document.

Feline URI Pathogens Incubation and Shedding Periods

  FHV FCV Chlamydia Bordetella M. felis Strep zoo
Incubation period ≤1 wk ≤1 wk ≤1 wk ≤1 wk ≤1 wk ≤1 wk
Shedding period <1 mo 1 to 3 mo <2 mo
w/o antibiotics
<3 mo
w/o antibiotics
w/o antibiotics
w/o antibiotics
Persistent infection yes yes (in some) no no unknown unknown


Feline respiratory pathogens are spread by three mechanisms: direct contact with sick cats, environmental and staff contamination (fomites), and contact with persistently infected asymptomatic cats that are shedding FHV or FCV. In contrast to canine respiratory pathogens, feline respiratory pathogens are not transmitted by aerosols. Sneezing cats generate large droplets that only travel 4 feet or less. This small shed and spread zone makes in-cage isolation in a general housing ward a feasible alternative to relocation of the cat to an isolation room. For in-cage isolation, the door can be covered with a towel to reduce spread of the pathogens outside of the cage.


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