Influenza (avian and other zoonotic)

Zoonotic influenza viruses, such as avian or swine influenza, normally spread in animals but can also infect humans. Human infections are primarily acquired through direct contact with infected animals or contaminated environments.

Avian, swine and other zoonotic influenza virus infections in humans may cause disease ranging from mild upper respiratory tract infections (fever and cough), to severe pneumonia, acute respiratory distress syndrome (breathing difficulties), shock and even death. Conjunctivitis (“pink eye”), gastrointestinal symptoms, encephalitis (inflammation of the brain) and encephalopathy (brain damage or disease) have also been reported to varying degrees depending on subtype.

While recently identified avian influenza viruses do not currently transmit easily from person to person, the ongoing circulation of these viruses in poultry is particularly concerning, as these viruses cause severe disease in humans and have the potential to mutate to become more contagious between people.

Avian, swine and other zoonotic influenza infections in humans may cause disease ranging from mild upper respiratory infection (fever and cough) to rapid progression to severe pneumonia, acute respiratory distress syndrome, shock and even death.

Gastrointestinal symptoms such as nausea, vomiting and diarrhea has been reported more frequently in A(H5N1) infection. Conjunctivitis has also been reported in influenza A(H7).

Disease features such as the incubation period, severity of symptoms and clinical outcome varies by the virus causing infection but mainly manifests with respiratory symptoms.

Evidence suggests that some antiviral drugs, notably neuraminidase inhibitor (oseltamivir, zanamivir), can reduce the duration of viral replication and improve prospects of survival, however ongoing clinical studies are needed. Emergence of oseltamivir resistance has been reported.