Thursday, January 19, 2023

WHO Update & Risk Assessment On Human H5N1 Infection - Ecuador


Eight days ago we learned from Ecuador's Ministry of Health that they had confirmed a human infection with clade H5N1  in a 9 year old girl - making her the first in South America, and the 7th globally. While few details were provided, the next day we learned from PAHO that her illness was serious:

The patient is currently hospitalized in a pediatric intensive care unit, in isolation and with antiviral and supportive treatment.

Up until a little over 3 weeks ago, we'd only known of 4 mild cases (1 UK, 1 US, 2 in Spain), but since then we've been made aware of a fatal case in China, and a severe infection of a child in Vietnam (see WHO Rapid Risk Assessment on A(H5N1) clade viruses).

Yesterday the WHO published their first update on the case, where we learn the girl - as of January 17th - was still in intensive care, in isolation, and receiving non-invasive mechanical ventilation. 

I've only posted some excerpts from a much longer report, so follow the link to read it in its entirety. 

Human infection caused by avian influenza A(H5) - Ecuador
18 January 2023

Situation at a glance

On 9 January 2023, WHO was notified of a human infection caused by an avian influenza A(H5) virus. The case, a nine-year-old girl, living in a rural area in the province of Bolívar, Ecuador, was in contact with backyard poultry, which was acquired a week before the onset of her symptoms. She is currently hospitalized, in isolation, and is being treated with antivirals.

This is the first reported case of human infection caused by avian influenza A(H5) virus in the Latin America and the Caribbean region. Work is ongoing to further characterize the virus.

Currently, available epidemiological and virological evidence suggests that influenza A(H5) viruses have not acquired the ability for sustained transmission among humans, thus the likelihood of human-to-human spread is low.

Description of the situation

On 9 January 2023, the Ecuador IHR National Focal Point (NFP) informed WHO of a human case of infection with an avian influenza A(H5) virus. The case was detected as part of severe acute respiratory infection (SARI) sentinel surveillance and was confirmed by the National Influenza Centre (NIC), the National Institute of Public Health Research (INSPI per its acronym in Spanish).

The case is a nine-year-old girl, with no known comorbidities, from Bolívar Province, Ecuador. She developed symptoms of conjunctival pruritus and coryza on 25 December 2022. On 27 December, she was brought to a local health center for medical evaluation and treatment. On 30 December, due to the persistent symptoms including nausea, vomiting and constipation, she was admitted to a general hospital where empirical treatment for meningitis was started with antibiotics and antipyretics. On 3 January 2023, she was transferred to a pediatric hospital in critical condition where she was admitted to the intensive care unit (ICU) with septic shock and was treated with antivirals and mechanical ventilation due to pneumonia.

On 5 January, as part of SARI surveillance activities, a nasopharyngeal sample was collected from the patient. The sample was sent to INSPI and tested positive for influenza A(H5) by reverse transcription-polymerase chain reaction (RT-PCR) on 7 January.

As of 17 January, the patient remains hospitalized, under isolation, and with noninvasive mechanical ventilation.

According to the epidemiological investigation in response to the outbreak, a week before the onset of her symptoms, the family acquired poultry which died without apparent cause on 19 December 2022. In addition, the epidemiological investigations revealed that several incidents of dead backyard poultry (chickens and ducks) have been reported from the same community where the family resided.


WHO risk assessment

This is the first reported case of human infection caused by avian influenza A(H5) virus in Ecuador and in Latin America and the Caribbean. This human case was exposed to poultry, which died without apparent cause. Outbreaks of highly pathogenic avian influenza have been detected recently in the provinces of Cotopaxi (influenza A(H5N1)) and Bolívar, Ecuador.

Whenever avian influenza viruses are circulating in poultry, there is a risk for sporadic infection and small clusters of human cases due to exposure to infected poultry or contaminated environments. Therefore, human cases are expected, although rare.

According to the information received thus far, the virus has not been detected in other individuals beyond this single case. While further characterization of the virus from this case is pending, currently available epidemiological and virological evidence suggests that influenza A(H5) viruses have not acquired the ability for sustained transmission among humans, thus the likelihood of human-to-human spread is low. Based on available information, WHO assesses the risk to the general population posed by this virus to be low. The risk assessment will be reviewed as needed should further epidemiological or virological information become available.

A global risk assessment associated with recent influenza A(H5N1) clade viruses was published on 21 December 2022. However, the subtype and clade information for this human case is not yet known.

There are no approved vaccines for preventing influenza A(H5) in humans. Candidate vaccines to prevent influenza A(H5) infection in humans have been developed for pandemic preparedness purposes.

Close analysis of the epidemiological situation, further characterization of the most recent viruses (human and poultry) and serological investigations are critical to assess associated risk and to adjust risk management measures in a timely manner.

          (Continue . . . )

Since this virus hasn't yet demonstrated the ability to transmit efficiently from human-to-human, the current threat to the general public is considered - based on the currently available evidence - to be low. 

But viruses mutate, so what we say about a virus today may not hold true tomorrow. 

A month ago, in the ECDC/EFSA Avian influenza overview September – December 2022 we learned that 8 new genotypes have appeared in Europe over the past 3 months, while in November we saw several new genotypes described in North America. 

These new genotypes can vary greatly in their ability to infect both avian and non-avian hosts, and in their virulence.  

It is a pretty safe assumption that in Asia, South America - and in many other parts of the world - additional genotypes are emerging, mostly outside of our view.  Most will provide no special advantage to the virus, and some may actually be detrimental to its survival.  

While the future evolution of these avian viruses is unknowable, the potential exists for the emergence of a biologically fit, and more dangerous virus.  

And so we follow these sporadic spillovers into humans with considerable interest.