According to Dr. Nirav Shah, Principal Deputy Director of the Centers for Disease Control and Prevention, laboratory investigations are continuing on the isolated and spontaneous case of H5N1 influenza diagnosed in a patient in Missouri.

In a September 13th release the CDC confirmed the  neuraminidase component of the virus as  N1.  Sequencing has yet to be completed although initial indications are that the virus belongs to clade 2.3.4.4b and is similar to the mammalian adapted H5N1 B3.13 strain circulating among dairy cattle and contacts including cats and rodents. The HA sequence disclosed two amino acid substitutions. According to a ProMED posting, Dr. Jesse Bloom at Fred Hutchinson Cancer Center, noted that the A156T mutation is associated with reduced neutralization of the H5N1virus with serum from a hyperimmunized ferret.

According to a ProMED Mail release, the patient presented with respiratory and itestinal symptoms including chest pain.  The initial hospital laboratory evaluation of the patient yielded a non-seasonal influenza-A virus that was referred to the Missouri State laboratory and then sent to the Centers for Disease Control. Treatment with antiviral medication and supportive therapy led to recovery and discharge. 

At this time, there does not appear to be any direct link between the patient and either livestock or consumption of unpasteurized milk.

The September 13th CDC release disclosed that a household contact developed respiratory symptoms on the same day as the patient subsequently followed by a health care worker. There were no attempt at isolation of an influenza virus from either of the contacts but it is hoped that subsequent serologic follow-up will determine whether malaise was attributed to previous exposure to H5N1. The patient and household member could have been infected from a common source. If the healthcare worker was in fact infected with H5N1, the suggestion of limited contagion in the hospital setting should be considered. 

Consistent with concerns over mutation of H5N1 to become zoonotic, the CDC has provided five companies with funding collectively amounting to $5 million to outsource influenza isolates for diagnosis and characterization.  Companies selected comprise Aegis Sciences, Arup Laboratories, Gingko Bioworks, Laboratory Corporation of America and Quest Diagnostics, all reputable clinical pathology or microbiological laboratories with experience in molecular assay of pathogens.

Health agencies led by CDC are obviously developing contingency plans and strengthening capabilities as a preemptive and precautionary measure in the event of an emergence of a zoonotic viral pathogen.  This is based on the deficiencies that were evident in 2020 following the emergence of SARS-CoV-19 virus responsible for COVID.

It is important to recognize that as of the present the Missouri case involving one individual who recovered represents an isolated event and that there is  no direct evidence of contagion to contacts.  There does not appear to be any upsurge in influenza in Missouri based on a review of the influenza database that will detect an increase in incidence rate.  It would be advisable to implement wastewater assay with specific attention to H5N1 strain influenza virus.