Belatedly, authorities in San Francisco reported on isolation of H5N1 avian influenza virus from asymptomatic chickens at a live bird market in San Francisco during late April. Concurrently, H5 RNA was detected in wastewater as reported by WastewaterSCAN although subsequent assays in May failed to reveal evidence of infection. To date, hospitals in San Francisco have not recorded any increase in admissions for influenza.
Monitoring for H5N1 is considered necessary given the extensive outbreaks of infection in poultry flocks in northern California and the emergence of bovine influenza-H5N1 that has now impacted close to 900 diagnosed herds in 12 states but has not yet emerged among the 1,300 dairy farms in California.
At this time, risks to humans are considered minimal given that there is no evidence of infection among workers at the implicated live bird market.
Dr. George Han, Director of Communicable Disease Prevention and Control at the San Francisco Department of Public Health, stated, “Essentially when there is an emerging virus, we work in the background to do our due diligence so that if there is a potential threat to human health we are on top of it.” Dr. Han emphasized “The most important thing to note is there is no threat to public health at this time”.
Live bird markets are an anachronism in the U.S. They continue as a source of infection including H5 and H7 strains in nations with an extensive network of marketing live-birds. Identifying flocks of origin following isolation of avian influenza virus in LBMs is complicated. The presence of the virus at the point of sale indicates infection in one or more supply flocks. At the present time, despite the low risk of human infection, LBMs represent a problem for commercial poultry since importing nations impose embargoes on counties or entire states with demonstrated infection.
LBMs that cater to ethnic minorities in urban areas should be phased out since commercial halal and kosher chicken is available that has been subject to state or federal inspection and marketed through a cold chain.