Bird Flu Case in Missouri Raises Questions
A patient in Missouri who was hospitalized with an infection of bird flu had the H5N1 strain of the virus, the US Centers for Disease Control and Prevention (CDC) confirmed on Friday. This case is significant because the individual had no known contact with infected animals, which is a departure from the usual pattern of H5N1 transmission.
The viral sequence of the Missouri case was uploaded to the GISAID database, which makes genetic sequences of viruses publicly available for research and study. The sequence shows that the virus is closely related to the strain that has been infecting dairy cattle in 14 states this year. However, the infected person reported no contact with wild birds, poultry, or cattle, and they did not consume raw dairy products.
This raises the question of how the person contracted the virus. The CDC is still investigating the source of the infection. It is important to note that all other human H5N1 infections reported in the US this year have been in people who had close contact with infected animals.
The genetic sequence of the virus does not indicate any changes that would make it more easily spread or cause more severe disease. However, the virus does have mutations that could affect the development of candidate vaccine viruses.
Further information about the Missouri case was posted in the CDC's weekly FluView report. The report revealed that a close household contact of the infected person got sick the same day with similar symptoms but was never tested. Both individuals have since recovered. The simultaneous development of symptoms suggests a common exposure rather than person-to-person spread.
A second close contact, a healthcare worker, developed mild symptoms but tested negative for the flu. No additional cases have been found after a 10-day follow-up period.
The confirmed patient in Missouri was an adult with multiple underlying medical conditions. They became ill in the week ending August 24th and were hospitalized due to their underlying conditions. While in the hospital, the patient tested positive for an influenza A virus. Routine additional testing on the sample determined that the person had an H5 virus, which is unusual. The sample was then forwarded to the CDC for confirmation.
The CDC considers the flu infection to be a contributing factor to the patient's hospitalization, not merely incidental. However, due to privacy concerns, the CDC declined to offer more information about the case.
CDC scientists noted that the patient sample they received contained a low concentration of the virus, which may limit their ability to sequence all eight segments of the virus.