Influenza C is a member of the family of viruses known for causing influenza or flu, a viral infection where people usually develop a fever, respiratory distress, chills, and muscle pains. This virus infects humans and pigs, and is sometimes known as swine influenza or swine flu. It tends to be associated with small, localized epidemics, and the severity of infections can vary, depending on the strain and the general health of the patient.
Influenza A and B are far more better known, and these viruses tend to attract the bulk of research. Influenza vaccines focus on A and B strains because they mutate quickly and evolutions can potentially be very dangerous. Influenza C usually causes a mild respiratory infection with some coughing and discomfort, resolving with rest and fluids and not requiring additional treatment.
People are more likely to contract influenza C when they work in close contact with pigs or live in communities where pork is handled regularly, such as employees of a pork processing plant or pork farmers. Often, the symptoms are so mild that people may not realize they are sick. In cases where they are more noticeable, they usually resolve within several days, sometimes without assistance from the patient. While people are ill, they can pass the influenza C virus on to other people they come into contact with.
Like all viruses, influenza C has the capacity to mutate and become more virulent. Researchers study it and archive samples for future reference. These can be useful when comparing epidemics, tracing the genetic history of the virus, and trying to identify viral patterns. For patients with compromised immune systems in whom an influenza C infection could be more dangerous, being able to identify the causative virus can be important for treatment, as it will allow care providers to select the best options for the patient.
Like many primarily mild viruses, influenza C can be seen at a low baseline level across the human population. Periodic flareups rarely spread far, and most people are typically only mildly ill when they are infected. Once infected, people build antibodies to the virus so they should not get sick with that strain again. It is important for people vulnerable to influenza infection to be aware that vaccinations will not protect them from all forms of the virus, but just those included in a seasonal vaccine. Outbreaks of rare strains could potentially be a cause for concern, as they may not have been included in the vaccine.