#15,566
Eight days ago, in Laos: First Reported H5N1 Human Infection In 18 Months, we learned of the first reported H5N1 infection of a human since a 21 y.o. man died, and subsequently tested positive in Nepal in March of 2019.
While not as feared as it once was - being largely overshadowed by H7N9 and H5N6 over the past 5 years - H5N1 viruses continue to evolve, reassort, circulate and occasionally infect humans.
H5N1 represents not just a single strain, but rather a growing array of clades, subclades, and variants that circulate around the globe (see chart below) - all demonstrating differing levels of pathogenicity and infection risk to humans and birds around the globe (see Differences In Virulence Between Closely Related H5N1 Strains).
This is only the 3rd case reported by Laos since 2005, and the first in 13 years. Given the comparatively large number of cases reported in neighboring Cambodia (n=56) and Vietnam (n=127) over the same time span, there are understandably doubts over the thoroughness of surveillance and reporting in the region.
While the trend with H5N1 has been downward since 2015, outbreaks in wild birds and poultry have continued to occur in places like Vietnam, the Middle East, and the Indian Subcontinent. The continued evolution and threat from H5N1 remains the subject of a number of recent studies, including:
Late yesterday the World Health Organization published DON (Disease Outbreak News) report on the recent case in Laos (see below). As always, in addition to the known details of the case, the WHO reminds nations of the importance of surveillance, testing, and the timely reporting of all novel flu detections.
While this is likely a one-off event, it is a reminder that nature's laboratory is open 24/7, and viral evolution never ends. Whether H5N1 will ever regain its former threat level remains to be seen, but even if it doesn't, there are always new threats in the wings.
Avian Influenza A(H5N1)- Lao People's Democratic Republic
Disease outbreak news
17 November 2020
The Ministry of Health in Lao People's Democratic Republic (PDR) reported a human case of infection with an avian influenza A(H5N1) virus. The case is a one-year-old female who developed symptoms of fever, productive cough, difficulty breathing and runny nose on 13 October 2020. She was hospitalized for her illness on 16 October and discharged on 19 October. As part of severe acute respiratory infection (SARI) sentinel surveillance, a specimen was collected on the date of hospitalization and confirmed to be positive for avian influenza A(H5N1) on 28 October by reverse transcription polymerase chain reaction (RT-PCR) at the National Centre for Laboratory and Epidemiology (NCLE).
Among the close contacts of the patient, one contact developed fever and cough after the onset of illness in the case. Specimens collected from all household contacts, including the symptomatic contact, were negative for influenza A viruses.
Upon further investigation, there were domestic poultry at the residence. There was no travel history of the family 14 days prior to symptom onset in the case.
This is the third human case of avian influenza A(H5N1) virus reported from Lao PDR since 2005; two cases including two deaths were reported in 2007.
Public health response
The government of Lao PDR has taken the following monitoring, prevention and control measures as detailed in the Joint National Preparedness and Contingency Plan for Avian influenza A(H7N9) and A(H5N1) for Lao PDR:
- Case management and isolation of cases and close contacts
- Testing of close contacts
- A meeting was conducted between the Provincial Health Department and the Provincial Department of Agriculture and Forestry to discuss and plan for the rapid response
- An epidemiological investigation is ongoing and includes with veterinarians from the Provincial Department of Agriculture and Forestry
- Risk communication has been initiated for the public and healthcare workers
- Strengthened surveillance and disinfection of the surrounding environment, including the patient’s residence and suspected exposure areas
- Laboratory samples will be shared with the WHO Collaboration Centre
WHO risk assessment
To date, 862 human cases of influenza A(H5N1) have been reported to WHO since 2003, including three from Lao PDR. Nearly all cases of avian influenza A(H5N1) infection in humans have been associated with close contact with infected live or dead birds, or influenza A(H5N1) virus-contaminated environments. Human infection can cause severe disease and has reportedly high mortality rate. Since the virus continues to be detected in poultry populations, further human cases can be expected.
Currently available epidemiologic and virologic evidence suggests that A(H5N1) viruses have not acquired the ability of sustained transmission among humans, thus the likelihood of human-to-human spread is low. Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. If this were to occur, further community level spread is considered unlikely as this virus has not acquired the ability to transmit easily among humans.
This case does not change the current WHO recommendations on public health measures and surveillance of influenza. Thorough investigation of every human infection with a un-subtypeable influenza A virus is essential.
WHO advice
Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global surveillance to detect virologic, epidemiologic and clinical changes associated with circulating influenza viruses that may affect human (or animal) health with timely sharing of such viruses and related information for further characterization and risk assessment.
All human infections caused by a novel influenza subtype are notifiable under the International Health Regulations (IHR) and State Parties to the IHR (2005) are required to immediately notify WHO of any laboratory-confirmed case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic. Evidence of illness is not required for this report .
In the case of a confirmed or suspected human infection caused by a novel influenza virus with pandemic potential, including a variant virus, a thorough epidemiological investigation (even while awaiting the confirmatory laboratory results) of history of exposure to animals, travel, and contact tracing should be conducted. The epidemiological investigation should include early identification of unusual respiratory events that could signal person-to-person transmission of the novel virus and clinical samples collected from the time and place that the case occurred should be tested and sent to a WHO Collaboration Center for further characterization.
General hygiene measures, such as regular hand washing before and after touching animals and potentially contaminated environments and avoiding contact with sick animals, should be adhered to. WHO does not recommend any specific different measures for travelers.
WHO does not advise special screening at points of entry regarding this event, nor does it recommend that any travel or trade restrictions be applied.
