Cambodia reports another human H5N1 avian flu case as Hong Kong notes H9 infection

News brief

Cambodia's health ministry has reported another human infection from H5N1 avian influenza, part of an uptick in similar cases that began in 2023.

backyard poultry
Juhan Sonin / Flickr cc

The patient is a 17-year-old girl from Kampot province, according to a ministry statement translated and posted by Avian Flu Diary, an infectious disease news blog. Kampot province is in southern Cambodia. The girl is hospitalized in the intensive care unit and is improving.

An investigation found that about 5 days before the girl's symptoms began, there were seven dead chickens at her home.

Cambodia has now reported 5 cases for 2024 and a total of 11 since February 2023, following nearly a decade with no human infections. Genetic sequencing on samples from several cases has revealed that the virus belongs to an older H5N1 clade ( that still circulates in poultry in some Asian countries, including Cambodia. It is different from the newer H5N1 clade ( that is currently affecting wild birds and poultry in multiple world regions, including the United States.

Hong Kong reports imported H9 case

Elsewhere, Hong Kong's Centre for Health Protection (CHP) today reported an influenza A H9 case, which involves a 22-month-old girl who had recently visited the city of Zhongshan in mainland China's Guangdong province. Her symptoms began on February 15, and she was seen at a hospital the next day but was not admitted. Plans are under way for her to receive care in hospital isolation.

An investigation revealed that she had no direct contact with poultry during her incubation period while visiting the mainland, nor did she eat undercooked poultry or have contact with sick people. One of her home contacts had a sore throat on February 17 that subsided.

The CHP said novel H9 flu virus infections, including H9N2, are typically mild. Hong Kong has reported nine cases since 1999, and its most recent case—from 2020—was also imported.

US study: Disparities in death rates persist after acute phase of pandemic

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A new research letter in JAMA Network Open demonstrates that pre-COVID disparities in all-cause mortality have largely persisted after the acute phase of the pandemic, as patterns have largely returned to baseline.

The study examined annualized age-standardized death rates (ASDRs) among major demographic groups in the United States from March 2018 through May 2023. Sex, race and ethnicity, metropolitan status, and region were all considered.

The authors compared mortality ratios between four periods: One year prior to the pandemic, the first and second years of the pandemic (before and after widespread vaccination), and the post-acute Omicron-dominant phase of the pandemic.

American Indian, Alaskan Native groups hit harder

During the pandemic, mortality rates increased significantly for men, people of color, non-urban residents, and people in the South and West. In almost all groups, levels returned to prepandemic levels by fourth period analyzed. However, the authors said a notable change was that American Indian or Alaska Native ASDRs compared to White mortality was 1.02 (1.01-1.03) to 1.20 (1.18-1.21) or higher in both acute pandemic years.

"Death rate ratios during the postacute period generally returned to prepandemic levels," the authors said. "Although mortality remains somewhat higher than before the pandemic, this additional mortality is largely proportional to 2018-2019 mortality with respect to major demographic comparisons.

This continuity suggests that these disparities are persistent; even a pandemic-level mortality shock does not permanently alter them.

"This continuity suggests that these disparities are persistent; even a pandemic-level mortality shock does not permanently alter them."

COVID vaccine mandates may have had unintended consequences, researchers say

News brief
COVID vaccination
Lubo Ivanko / iStock

US state COVID-19 vaccine mandates didn't significantly change uptake, and states with mandates actually had lower COVID-19 booster and voluntary adult and child flu vaccine coverage than those that banned vaccine requirements, an analysis of Centers for Disease Control and Prevention (CDC) data suggests.

Researchers from the University of Arizona at Tucson and Furman University in South Carolina parsed the data to identify changes in COVID-19 vaccination rates and COVID-19 boosters and seasonal flu vaccines in the 2 months before and after implementation of state-level mandates for targeted groups (eg, state employees). Baseline attitudes were collected before the vaccine rollout as part of the COVID States Project.

Challenges of promoting public health via vaccines

In the 19 states with COVID-19 vaccine mandates, weekly COVID-19 vaccination rates weren't statistically significantly different before and after mandate implementation, and the difference in vaccination rates from before to after mandates didn't depend on baseline attitudes toward the requirements. The authors noted that the analysis wasn't sufficiently powered to detect small effects.

A series of multilevel models were tested to compare state-level differences in weekly COVID-19 booster uptake from rollout in November 2021 to May 2022 in mandate states and in the 22 states that outlawed such mandates. The results suggested that the percentage of eligible residents who received a booster was smaller in mandate states than in those that banned mandates. The difference was greater among states with lower vaccination levels.

The results underscore the challenges of promoting public health through vaccination.

An examination of two CDC datasets on state-level flu vaccination among adults and children in the 2021-22 flu season showed that both adults and children in mandate states were less likely to receive the flu vaccine than those in states with mandate bans.

"This research supports the notion that governmental restrictions in the form of vaccination mandates can have unintended negative consequences, not necessarily by reducing uptake of the mandated vaccine, but by reducing adoption of other voluntary vaccines," the study authors wrote. "More broadly, the results underscore the challenges of promoting public health through vaccination."

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