H7N2 is a subtype of the influenza A virus that circulates among birds. Its designation refers to the proteins on its surface: hemagglutinin (H7) and neuraminidase (N2), which allow the virus to infect host cells. While H7N2 is an avian influenza, or “bird flu,” it can cross the species barrier to infect mammals. Infrequent human cases have been documented, highlighting its zoonotic potential.
H7N2 in Animal Populations
Wild aquatic birds, such as ducks and shorebirds, are the natural reservoirs for H7N2. In these wild populations, the virus often exists without causing significant illness. The primary concern arises when the virus spreads to domestic poultry, including chickens and turkeys. Transmission occurs through direct contact with infected birds or indirectly through contaminated environments.
Most H7N2 strains are Low Pathogenic Avian Influenza (LPAI), causing mild or no symptoms in poultry, such as ruffled feathers or a drop in egg production. However, H7 viruses can mutate into Highly Pathogenic Avian Influenza (HPAI) strains. HPAI is more dangerous, causing severe disease and high mortality rates in poultry, often within 48 hours.
Human Infection Risks and Symptoms
Human infections with H7N2 are uncommon, occurring after direct contact with infected birds or their contaminated surroundings. Activities like handling, slaughtering, or de-feathering infected poultry pose the highest risk. The virus can enter the body through the eyes, nose, or mouth, but person-to-person transmission has not been a feature of this subtype.
When human infections occur, the illness is mild. The most frequently reported symptom is conjunctivitis, an inflammation of the membrane covering the eye. Other symptoms can include fever and upper respiratory issues similar to a common cold. Serious complications are possible, particularly for individuals with compromised immune systems.
The virus does not easily adapt to humans because the cellular receptors in our respiratory tract differ from those in birds. Public health agencies monitor H7 viruses for their potential to evolve and more readily infect people.
Notable H7N2 Occurrences
A 2002 H7N2 outbreak in Virginia, West Virginia, and North Carolina spread to 197 commercial poultry farms, leading to the culling of 4.7 million birds to control the disease. One person involved in the control operations was infected with the virus but made a full recovery.
Another notable instance was a 2016 outbreak among cats in New York City animal shelters. The virus caused respiratory illness and demonstrated rare cat-to-human transmission when a veterinarian with prolonged exposure to sick cats contracted a mild case. Other isolated human cases have been reported, including one in New York in 2003 where the infection source was unknown.
Prevention and Control Strategies
Preventing H7N2 spread involves farm biosecurity and public health measures. Poultry operations use strict protocols to prevent the virus’s introduction, including limiting farm access, disinfecting equipment, and stopping contact between domestic and wild birds. Surveillance programs also test birds for early detection.
If an outbreak is detected, control measures include establishing quarantine zones and culling infected flocks to stop further spread. For the public, good hygiene is the primary prevention method. This includes frequent handwashing with soap and water, especially after contact with birds or potentially contaminated areas.