#18,182
Yesterday PAHO (Pan American Health Organization), in conjunction with the WHO, released a public health risk assessment on the zoonotic spread of H5N1 in the Americas. These types of assessments - while they can be useful - are only as good as the data used to make them.
And unfortunately, surveillance and reporting continues to erode, both in the United States, and around the globe (see No News Is . . . Now Commonplace).
Yesterday we learned that Oklahoma had become the 13th state to detect HPAI H5 in dairy cows, but this was based on samples collected last April, and only recently submitted to the USDA for testing.
Nearly every WHO DON or disease Situation Report contains diplomatic reminders to member nations of their `duty to report' these types of cases under the IHR 2005 agreement, but compliance remains spotty at best.Testing of livestock remains largely voluntary (except for interstate transport of cattle), and no one really knows how widespread the virus is in cattle across the nation.
Just over 18 months ago, in Flying Blind In The Viral Storm, we looked at the increasing willingness of many countries to delay, downplay, or hide reports of emerging infectious disease events, and it is arguably even more pervasive today.
Last week, the Director-General of WHO made another in a long list of appeals to nations to take the H5N1 threat seriously, and to immediately report any outbreak of zoonotic influenza.
Last week, the United States reported a fourth human case of H5N1 following exposure to infected dairy cows.
Cambodia also reported two cases in children who had contact with sick or dead chickens.
For the moment, no human-to-human transmission has been reported, which is why WHO continues to assess the risk to the general public as low.
However, our ability to assess and manage that risk is compromised by limited surveillance for influenza viruses in animals globally.
Understanding how these viruses are spreading and changing in animals is essential for identifying any changes that might increase the risk of outbreaks in humans, or the potential for a pandemic.
- WHO calls on all countries to strengthen influenza surveillance and reporting in animals and humans;
- To share samples of influenza viruses with WHO Collaborating Centres;
- To share genetic sequences of human and animal flu viruses with publicly accessible databases;
- To provide protection for farm workers who may be exposed to infected animals;
- To accelerate research on avian influenza;
- And to encourage closer cooperation between the animal and human health sectors.
Despite the risks to public health, `don't test, don't tell' remains an attractive option for many countries, and industries. `Bad news', if it is released at all, is often done so strategically or belatedly.
It is against this backdrop of limited data that we get the following risk assessment from PAHO, which cites only `moderate confidence' in available information in making their determination.
I've only reproduced the summary from this 11-page Risk Assessment, so follow the link to read it in its entirety. I'll have a brief postscript after the break.
12 July 2024
Date of risk assessment: 9 July 2024
Risk statement
The purpose of this regional rapid risk assessment (RRA) is to assess the current public health risk to human health associated with the introduction and expansion of zoonotic avian influenza A(H5N1) clade 2.3.4.4b in mammals species in the Region of the Americas.
The RRA has been conducted taking into account the following criteria: (i) the risk of virus dissemination, specifically the potential occurrence in further countries in North America, Central America, South America, and in the Caribbean of events in dairy cattle and related spillovers to other mammals; (ii) the risk to human health including the risk of human exposure to infected animals and contaminated environments, the potential worsening of clinical and epidemiological characteristics of the disease if the virus further adapts to humans and/or other mammals, the potential for increased mammalian susceptibility from genomic mutations and viral reassortment, as well as risk factors for the occurrence of human infections and determinants related to outbreaks in animals; and (iii) the risk to public health based on the varying levels of capacities for early detection, prevention, and response with a One Health approach within the region, as well as the challenges in the implementation and adaptation of control measures (encompassing response capabilities, surveillance, diagnostic techniques, health and animal service preparedness, and medical supplies with available resources).
The overall risk in the general population of this event for the Region of the Americas to human health is classified as “Low” with a level of confidence in the available information of “Moderate”, for the following reasons:
Epidemiological and virological factors:
Current epidemiological data indicate localized occurrences of avian influenza A(H5N1) clade 2.3.4.4b in dairy cattle herds within the United States of America, with spillover into humans and other mammals in direct contact. Virologically, the virus remains predominantly bound to avian-type receptors, limiting its transmissibility to humans via respiratory droplets or fomites, as demonstrated by recent studies. A substantial component of the risk of spread throughout the Region of Americas has, and will continue to be, predominantly from wild birds however, after introduction in cattle, the continuous transmission between the different states in the United States has evidenced other mechanisms of transmission (e.g., movement of cattle). Even with no further change in the virus there are likely to be additional outbreaks in mammals, and sporadic cases reported in humans. The recent global risk, given the same parameters, has been considered to be low by the World Health Organization (WHO), but requiring vigilance and ongoing monitoring (1-3).
Capacity for surveillance and response:
The Region of the Americas benefits from robust pandemic preparedness initiatives led by Pan American Health Organization (PAHO), including the WHO Pandemic Influenza Preparedness (PIP) Framework and Preparedness and Resilience for Emerging Threats (PRET) initiative. PIP and PRET strengthens regional capacities for early detection, surveillance, vaccine deployment and response to zoonotic influenza outbreaks thereby mitigating the potential impact of localized influenza outbreaks and enhancing the region’s readiness to manage any potential spread (4). However, it is prudent for countries to enhance event-based surveillance mechanisms at the animal-human interface and continue to monitor influenza through its network of influenza-like illness (ILI) and severe acute respiratory infections (SARI) surveillance sites.
The available evidence supports a coordinated regional risk assessment of “low” for the general population and “low-to-moderate” for occupationally exposed individuals.
The rapid risk assessment will be reviewed should further epidemiological or virological information become available
The risk assessment of “low” for the general population and “low-to-moderate” for occupationally exposed individuals seems reasonable, at least based on currently available information.
But, as the WHO warns: their ability to assess the risks is compromised by limited surveillance.
So while the risks are currently deemed to be `low', we can't afford to be lulled into complacency.
