PAHO: Updated Epidemiological Alert On HPAI H5N1 (March 13th)

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Overnight PAHO (the Pan American Health Organization) released their latest Epidemiological Alert on the increasing threat from HPAI H5N1.  The virus first appeared in South America (Colombia) in early October, and has steadily made its way south and east across the continent (see timeline graphic below). 

With 16 countries (see chart below) in the Americas now reporting HPAI H5 either in wild birds, poultry, or mammals, the virus has already become remarkably well-entrenched across much of the Western Hemisphere.  

Given the limits of surveillance and reporting, particularly from some of the more remote regions of the Americas, it is likely that the virus has made inroads in some nations or regions not yet on this list.  

While only 1 human infection has been confirmed in South America so far, a recently published account of the investigation (see J. Trvl. Med. Research Letter) showed that case was very nearly missed.  

A less severe (or non-hospitalized) infection could easily have escaped attention. 

Some excerpts from PAHO's updated 23-page Epi Alert follows, but you'll want to download and read the entire document. 

Epidemiological Alert
Outbreaks of avian influenza caused by influenza A(H5N1) in the Region of the Americas

13 March 2023

Given the increasing detection of outbreaks of highly pathogenic avian influenza (HPAI) in birds registered in 16 countries of the Region of the Americas, the confirmation of the first human infection of influenza A(H5N1) in Latin America and the Caribbean, and the increase of cases in mammals, the Pan American Health Organization/World Health Organization (PAHO/WHO) reiterates its guidelines on surveillance, laboratory diagnostics in human and animal samples and research. PAHO/WHO recommends strengthening surveillance of respiratory disease in animal and human populations, thorough investigation of all zoonotic infections, and pandemic influenza preparedness.

(SNIP)

Guidance for health authorities in Member States

Both HPAI and LPAI viruses can be rapidly spread among poultry through direct contact with infected waterfowl or other poultry, or through direct contact with fomites or surfaces, or water contaminated with the viruses. Infection of poultry with HPAI viruses can cause severe disease with high mortality. LPAI viruses are more associated with subclinical infection. The terms HPAI and LPAI apply only to the symptoms in birds (chickens in particular), and both types of viruses have the potential to cause severe infections in humans.

While the potential exists for these viruses to cause human infections, infections with avian influenza viruses are punctual and when they have occurred, these viruses have not spread easily from person-to-person. To date, no person-to-person human transmission caused by avian influenza A(H5N8), A(H5N2), or A(H5N1) viruses has been reported either in the Americas or globally.

Intersectoral coordination

Control of the disease in animals is the first measure to reduce the risk to humans. For this reason, it is important that prevention and control actions, both in the animal and human health sectors, are carried out in a coordinated and concerted manner. Agile information exchange mechanisms will have to be established and/or strengthened to facilitate coordinated decision-making.

Implementation of a comprehensive surveillance program, including wild birds and both backyard and commercial poultry, is essential. Targeted risk-based surveillance strategies should be combined with a strengthening of general surveillance. In this regard, sensor awareness tasks are key, particularly in the backyard, to encourage the detection and notification of suspicious events. These programs also provide information that enables spread modeling and more accurate risk analysis.

Comprehensive recommendations for strengthening intersectoral work on surveillance, early detection, and investigation of influenza events at the human-animal interface are available at: https://bit.ly/3glEUNN

(SNIP)

Surveillance in humans

People at risk of contracting infections are those directly or indirectly exposed to infected birds (domestic, wild, or captive), for example, poultry keepers who maintain close and regular contact with infected birds or during slaughter or cleaning and disinfection of affected farms. For this reason, the use of adequate personal protective equipment (PPE) and other protection measures is recommended to avoid zoonotic transmission in these operators.

Surveillance and monitoring of exposed persons is recommended to early identify cases or events of human-animal interface transmission. Due to the constantly evolving nature of influenza viruses, PAHO/WHO continues to emphasize the importance of strengthening severe acute respiratory infection (SARI) surveillance and influenza syndrome (ILI) surveillance to detect virologic, epidemiologic, and clinical changes associated with circulating influenza viruses that may affect human health.

In addition to the active case-finding, identification and contact tracing activities carried out during the epidemiological investigation of zoonotic events, it is advisable to strengthen existing SARI and ITI surveillance systems in locations where poultry farms are located, where cases reside, where animal outbreaks occur, or where the source of infection is suspected. To complement surveillance for SARI and ILI, PAHO/WHO recommends establishing early warning systems to provide an overview of the situation and to carry out a joint and coordinated risk assessment between the human and animal sectors in a timely manner.

Given the detection of an infection in humans, early notification is essential for an investigation and implementation of adequate measures that include the early isolation and treatment of the case, the active search for other cases associated with the outbreak, as well as the identification of close contacts for management and follow-up (74).

Healthcare personnel in areas where transmission of avian influenza (HPAI or LPAI) in birds is taking place should be alerted about the possibility of infection in people exposed to these viruses.

PAHO/WHO reiterates to Member States the need to maintain and strengthen seasonal and zoonotic influenza virus surveillance, including immediate shipment of human influenza samples caused by avian influenza to the WHO Collaborating Center, the US CDC.

Since information on the circulation of avian influenza A(H5N1) viruses is important for the human zoonotic influenza vaccine composition and for generating data for preparedness and response, countries are encouraged to share animal influenza samples with the WHO Collaborating Center, St. Jude Children’s Hospital, which focuses exclusively on the threat to humans from zoonotic influenza viruses. 

          (Continue . . . )

It is no secret that the quantity and quality of infectious disease reporting around the globe has suffered over the past 3 years as the COVID pandemic exhausted resources and busted budgets. Last December, in Flying Blind In The Viral Storm, we looked at some of these growing surveillance gaps, and the risks they impose. 

Even in developed nations, public health officials openly admit that their ability to detect sporadic human cases of H5N1 is limited (see UK APHA: Technical risk assessment for avian influenza (human health): influenza A H5N1 2.3.4.4b).

Nations can only do what they can do, with the resources they have available. While the calls for increased surveillance and reporting are vital if we hope to have early warning of a change in the virus's behavior, the ability of countries to deliver will vary widely.  

So far, the good news is we've not seen any evidence that HPAI H5 is transmitting efficiently in humans, or of any community spread. Unless, and until that happens, avian flu presents a very low threat to public health. 

But the virus continues to reassort, and evolve into dozens of new genotypes, so what we say about the virus today may not hold true tomorrow.  

Stay tuned.