On July 29, NACCHO hosted a webinar with subject matter experts who presented overviews of the current situations with dengue and H5N1, also known as highly pathogenic avian influenza (HPAI). This recap distills key information and provides local health departments with actionable resources. By leveraging these tools, health departments can enhance their readiness and response capabilities to protect their communities in the case of an outbreak.
Dengue
Dr. Lyle Petersen shared CDC’s approach and guidance on the rising incidence of dengue virus (DENV) cases in the United States. This included an overview of the historical burden of disease, response guidance for investigations in non-endemic areas, and recommendations by risk level. A summary of the guidance can be found here.
Dengue is the most common mosquito-spread disease in the world and is on the rise this year. On June 25, CDC’s Emergency Preparedness and Response released a Health Alert Network (HAN) advisory of increased risk of dengue infection in the United States. Dr. Petersen opened the webinar by highlighting the sharp increase in cases. The incidence of dengue has been the highest ever recorded this year. In the Americas, from January 1 to June 24, 2024, there have been more than twice as many cases as in 2023, raising the number of cases in the Americas from 4.6 million in 2023 to over 11 million as of August 8, 2024.
Dr. Petersen discussed the current guidance for investigating suspected dengue cases in non-endemic areas of the United States. There are two main components of categorizing risk levels to determine which recommendations apply to the situation.
1. Identify if the case meets laboratory criteria for recent dengue virus (DENV) infection.
- Confirmed DENV infection: Positive nucleic acid amplification test (NAAT/PCR) or NS1 antigen test, or change from negative to positive IgM or IgG antibody result in paired sample
- Probable DENV infection: Positive IgM antibodies
2. Find out if the person traveled to an area with active DENV transmission in the two weeks before symptom onset.
- Yes: See considerations for travel associated cases
- No: If a locally acquired case is suspected in a non-endemic area:
- Investigate all possible routes of transmission and try to confirm DENV infection, if possible
These actions will help determine infection status in symptomatic individuals and dengue transmission risk levels. Dr. Petersen also highlighted risk factors for local dengue transmission, including:
- High number of travel-associated dengue cases (Ex: >10 cases per year),
- High human population density,
- Higher numbers of Aedes vector breeding sites (Ex: small backyard containers, neglected swimming pools, discarded tires),
- High precipitation, warm temperatures (average daytime temperatures between 68-95 °F), and lower elevation (<6,000 ft).
The dengue guidance presented by Dr. Petersen shares recommendations for the public, healthcare providers, and suspected cases in areas with low, moderate, and high probabilities of dengue transmission. These recommendations aim to bolster awareness, prevention, and response strategies.
The webinar also included specific steps for responding to locally acquired dengue. The six actions areas most important for locally acquired DENV include:
- Investigation
- Coordination
- Vector control
- Enhanced surveillance
- Healthcare provider outreach
- Reporting
Additionally, Dr. Petersen outlined some strategies to control Aedes mosquitoes, recommendations for entomological surveillance, virologic surveillance in mosquitoes, and scaling activities to multiple areas. Partners can assist by raising awareness about the increased risk of dengue and recommending that clinicians order FDA-approved testing for dengue.
CDC is committed to supporting state and local health departments in their efforts to prepare for and respond to DENV transmission. By implementing the guidance and strategies discussed in the webinar, health departments can enhance their readiness and promote effective responses to dengue outbreaks, protecting their communities and mitigating the impact of DENV overall.
Highly pathogenic avian influenza A virus (HPAI) | H5N1
CDC HPAI updates
The presentation transitioned to an update from CDC on H5N1, also known as highly pathogenic avian influenza A virus (HPAI), from Dr. Sonja Olsen and Erin Burns. Dr. Olsen shared updates about the current (as of June 29) situation and what CDC’s technical response has been. Erin Burns presented CDC’s strategy for communicating essential information to diverse stakeholders and provided a range of CDC resources tailored to different audiences. These can be found in the resource repository. Their presentation can be found here.
HPAI A (H5N1) virus was first identified in dairy cattle in March 2024 and has been confirmed in over 170 farms across 13 states as of mid-July. Fourteen human cases have been reported since 2022, and 13 are associated with the 2024 outbreak in animals—nine associated with poultry exposure and four with dairy cattle exposure. As of July 2024, there has been no evidence of human-to-human transmission, and all human cases have been clinically mild, with no hospitalizations.
As of July 2024, there has been no evidence of human-to-human transmission, and all human cases have been clinically mild, with no hospitalizations.
The virus retains primarily avian genetic characteristics and currently lacks traits that would enhance its ability to infect or spread among humans. There are no known markers of resistance to FDA-approved antiviral drugs, and since the virus closely resembles existing candidate vaccine strains, a vaccine could be developed if needed.
CDC maintains a comprehensive surveillance system with state and local health partners, and as of July 2024, no unusual influenza indicators, including avian influenza A(H5N1), have been detected. Overall, the risk to the public remains low, but those with significant exposure to infected animals or contaminated environments are at higher risk. Exposed individuals are advised to monitor for symptoms following their initial exposure and for ten days afterward.
In communicating the risk of H5N1, it is important to emphasize that while the immediate risk to the public is low, those with significant exposure have a higher risk of infection. Flu viruses are continually evolving, and future cases could potentially involve more severe illness. The CDC is actively engaging with farmworkers through various platforms in English and Spanish to raise awareness about H5N1 and provide communication resources in multiple languages.
Like with dengue, CDC is committed to supporting state and local health departments in their efforts to prepare for and respond to H5N1 (HPAI). By utilizing the information and resources shared, local health departments can enhance their readiness and response capabilities for H5N1, ultimately protecting their communities and mitigating the overall impact of the virus.
Colorado Department of Public Health and Environment (CDPHE)
The webinar concluded with a presentation by Dr. Alexis Burakoff from the Colorado Department of Public Health and Environment (CDPHE). Dr. Burakoff described how Colorado responded to and mitigated the impact of the avian flu outbreak in the state. Since late April, more than half of Colorado’s dairy farms and a few commercial poultry farms have been affected by the avian flu.
CDPHE mobilized teams to respond to affected farms. This response includes testing symptomatic workers, providing oseltamivir (Tamiflu), providing personal protective equipment, and providing ongoing monitoring of the workers. Ten human cases of H5N1 associated with dairy and poultry work have been identified as of August 20. All affected individuals presented with only mild symptoms. No evidence of person-to-person transmission has been detected.
Local public health agencies played key roles in the response, including symptom monitoring of some workers in their jurisdictions, assisting with on-site field visits to dairies, aiding in PPE distribution and educational outreach, and facilitating symptomatic individual testing.
In addition, six domestic cats have tested positive for H5N1 in the same region of Colorado. Household contacts have been monitored for any symptoms of illness. Domestic animals (e.g., cats, dogs) can develop avian flu if they are exposed to sick or dead birds or an environment contaminated with H5N1. People should follow these recommendations for prevention and steps if an animal is sick following contact with suspected avian flu. Colorado also has guidance for veterinarians on assessing H5N1 in domestic cats.
With the support of local, state, and federal partners, CDPHE mobilized teams swiftly to protect public health and continues to monitor the situation with teams prepared to test and assess for illness, as needed. As part of the response, CDPHE is also testing workers with and without symptoms for antibodies to determine if any infections might have gone undetected. Preparedness work continues for possible future outbreaks or changes to the virus that require different strategies for mitigation.
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NACCHO thanks CDC and CDPHE for providing their insights during this webinar. Federally, CDC continues to monitor the situation with H5N1 and dengue and partner with state and local health departments.
Below are resources shared by CDC during the presentation that can inform your efforts to prevent and respond to these viruses.
If you have any questions or want to share your local health department story, contact Kimberly Nalley, MPH, Senior Program Analyst on NACCHO’s Infectious Disease team at [email protected].
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Resource repository from the presentations
Dengue resources
Dengue fact sheets
HPAI (H5N1) resources
- Webinar slides: Olsen and Burns Presentation Slides
- Situation Updates: CDC A(H5N1) Bird Flu Response Update | Avian Influenza (Flu)
- Surveillance Updates: How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation | Avian Influenza (Flu)
- Technical Report: Highly Pathogenic Avian Influenza A(H5N1) Viruses | Avian Influenza (Flu) (cdc.gov)
- Updated Recommendations:
HPAI communications resources
Other key HPAI resources with translations
- Spanish: Protect yourself Spanish
- K’iche’: Protect yourself K’iche’
- Nahuatl: Protect yourself Nahuatl
- Haitian Creole: Protect yourself Haitian Creole
- Spanish resource: factsheet-farm-workers-spanish.pdf (cdc.gov)
- Spanish resource: infographic-cows-spread-flu-spanish.jpg (1650×1275) (cdc.gov)