Missouri - Credit Wikipedia
#18,296
In addition to the revelation earlier today of an untested, but symptomatic close contact to the Missouri H5 case (see CDC FluView Update On Missouri H5 Case Adds An Important Detail), late today the CDC released a more detailed report which mentions a 2nd symptomatic close contact (who reportedly tested negative for flu).
It isn't stated what kind of flu testing was conducted on this second contact, or at what stage in that person's illness swabs were collected, both of which could affect the accuracy of the test (see CDC: Updated RIDT Guidance - When `No’ Doesn’t Always Mean No).
Since both appear to have been ill at roughly the same time as the confirmed case - even if they had H5 - this would be more suggestive of a `shared exposure' than human-to-human transmission. It is possible that antibody testing could yield more information in the weeks ahead, assuming these contacts are willing to participate.
I've already commented in my last blog on the slow-rolling of data, so I won't repeat that again.
I've reproduced excerpts from today's update below, but you'll want to follow the link to read the full update.
CDC A(H5N1) Bird Flu Response Update September 13, 2024
(excerpt)
Missouri Case Update
Missouri continues to lead the investigation into the H5 case reported last week with technical assistance from CDC in Atlanta. The case was in a person who was hospitalized as a result of significant underlying medical conditions. They presented with chest pain, nausea, vomiting, diarrhea, and weakness. The person was not severely ill, nor were they in the intensive care unit. They were treated with influenza antiviral medications, subsequently discharged, and have since recovered. One household contact of the patient became ill with similar symptoms on the same day as the case, was not tested, and has since recovered. The simultaneous development of symptoms does not support person-to-person spread but suggests a common exposure. Also shared by Missouri, subsequently, a second close contact of the case – a health care worker – developed mild symptoms and tested negative for flu. A 10-day follow-up period has since passed, and no additional cases have been found. There is no epidemiologic evidence to support person-to-person transmission of H5 at this time. CDC's original report about the case in Missouri is available: CDC Confirms Human H5 Bird Flu Case in Missouri | CDC Newsroom.
CDC has attempted to sequence the full genome of the virus from the most recent case of H5 reported by Missouri. Because of low amounts of genetic material (viral RNA) in the clinical specimen, sequencing produced limited data for analyses. Full-length gene sequences were obtained for the matrix gene (M) and non-structural (NS) genes and partial gene sequences were obtained for the hemagglutinin (HA) and neuraminidase (NA) genes. The available gene sequences are all closely related to U.S. dairy cow viruses, and similar sequences have been found in birds and other animals around dairy farms, raw milk, and poultry.
The HA gene sequence confirms that the virus is clade 2.3.4.4b, and the NA sequence was confirmed as N1. There are two amino acid differences in the HA that have not been seen in sequences from previous human cases. These amino acid differences are not known to be associated with changes to the virus's ability to infect and spread among people. However, both differences are in locations that may impact the cross-reactivity of clade 2.3.4.4b candidate vaccine viruses (CVVs). Additional antigenic testing is planned. One of the two amino acid differences (HA A156T) has been identified in fewer than 1 percent of viruses detected in dairy cows. The other amino acid difference (HA P136S) has been seen in only a single dairy cow sequence.
In addition to the HA analysis, no markers of reduced susceptibility to neuraminidase inhibitors and no markers of mammalian adaptation were found. These findings suggest that currently available neuraminidase inhibitors for influenza are expected to maintain their effectiveness and that the virus from this person does not show signs of increased potential to spread from person to person. Sequence data for A/Missouri/121/2024 was submitted to GISAID (EPI_ISL_19413343) and GenBank (not yet available). Additionally, multiple attempts to propagate virus from the clinical specimen were not successful.
Also, since the last update, CDC performed antiviral susceptibility testing of avian influenza A(H5N1) viruses isolated from the previously reported human cases associated with poultry exposure in Colorado. All of the virus specimens were determined to be susceptible to FDA-approved and recommended antivirals (oseltamivir, zanamivir, peramivir, and baloxavir).
