Avian Flu. How Dangerous is for Humans?

Avian flu

Last Updated on 27 March 2023

A few days ago, WHO General Director Tedros Adhanom Ghebreyesus warned the entire world about the risk of a potentially dangerous avian flu pandemic among humans. The fear went off after a strain of H5N1 virus jumped from birds to mammals.

“The avian flu virus is an extremely flexible pathogen. – Dr. Calogero Terregino, Director of the National and European Reference Center for Avian Flu at the Istituto Zooprofilattico Sperimentale delle Venezie in Italy, said. – For this reason, WHO launched the alarm”.

Transmission in Animals

“In Italy, – the doctor continued – avian flu affected 30 domestic birds in the early months of this year, while last year, the cases were 317”.

“The most severe condition is in wild birds and mammals. There are many cases of infection among these species of animals”.

Avian flu outbreaks in mammals have been reported in the UK and Spain. The British cases regard seals, which suffered the virus spillover, namely transmission from bird to seal.

The highest number of cases has been reported in Spain, where in October 2022, 50,000 farmed minks were tested positive and killed for an infection from H5N1 virus.

The bird – mammal contagion makes avian flu closer to human transmission.

bird flu

“The bird-mammal transmission- Dr. Terregino said- means that the virus has had genetic mutations. What we observed in the infected mammals is remarkable, but these strains seem still unable to infect humans”.

Farmed animals end up infected for the scanty conditions of the places where they are kept and for being fed with raw poultry. Even wild animals may be affected because often they eat dead bird carcasses.

However, just these days, the situation is raising worries in the UK, where tons of domestic birds have died from avian flu. Now, scientists suggest isolating the bird keepers in order to not come into contact with the virus.

Human Transmission

Upon a certain point of view, it seems that now, the human transmission of avian flu is at the gates, but Dr. Matteo Bassetti, Head of Infectious Diseases of the San Martino Hospital in Genoa, intervenes to clarify the matter.

“Of course, the avian flu virus has rarely infected humans so far – Dr. Bassetti said – However, when this happens, H5N1 virus has a fatality rate of 56%, while Covid-19 had only a fatality rate of 3%. It means that of two avian flu infected, one dies”.

“It is not wrong if we believe that another deadly pandemic could occur. – Dr. Bassetti warns – But we mustn’t waste our time. We need to invest in H5N1 vaccines, already approved by FDA, and be ready to produce them in large quantities and in a very short run, because we can’t wait six months to get vaccines on a large scale. We must also invest in antiviral medications to have them at disposal when it is necessary. To figure out if something is going bad, we must also keep testing, especially when humans come into contact with birds.”

But what are the true reported cases of avian flu among humans? Here are the official data.

Reported Cases of Human Infection with Avian Flu

According to the weekly bulletin by Who, released at the end of January, and integrally reported here, “as of 26 January 2023, a total of 240 cases of human infection with avian influenza A(H5N1) virus have been reported from four countries within the Western Pacific Region (since January 2003)”, namely: Cambodia, China, Laos and Vietnam.

“Of these cases, 135 were fatal, resulting in a case fatality rate (CFR) of 56%. The last case was reported from China, with an onset date of 22 September 2022 and died on 18 October 2022. This is the first case of avian influenza A(H5N1) reported from China since 2015.

Globally, from January 2003 to 25 November 2022, there have been 868 cases of human infection with avian influenza A(H5N1) virus reported from 21 countries. Of these 868 cases, 457 were fatal (fatality rate of 53%)”.

On a general level, most avian flu cases among humans relate to the 2.3.4.4b H5N1 virus variant. That is the most widespread variant of the virus, which caused a few isolated and asymptomatic cases in Europe.

There is also to underline that the H5N1 virus is the avian flu strain which is more capable of causing a deadly infection.

The most recent case, according to the data reported by Dr. Terregino, occurred this year, in January, in Ecuador, where a 9-year-old little girl, infected by a variant of H5N1 virus, has been hospitalized in the local unit of intensive care.

But further cases of human infection may happen because of other avian flu strains. Below is the complete list of bird flu viruses published in the WHO weekly update.

Avian Flu Viruses: Human Contagion Roadmap

Avian flu H5N6 virus caused no human infection this year. The total cases confirmed since 2014 are 83, including 33 deaths.

Avian flu H5 virus caused no infection among humans this year, with only a case, with no death, reported in October 2022.

Avian flu H3N8 virus has caused two human infections so far, and no death.

No human infection also for the avian flu H7N4 virus up to now, only one confirmed case in China, dating back to 2018.

A bit of concern has been raised by an avian flu subtype, the H7N9 virus, which caused 1568 cases of human infection with 616 deaths (fatality rate 39%) in China in the pre-pandemic years, with the latest case reported in 2019.

But particularly interesting is the statement of the World Health Organization about the level of risk of this subtype of H7N9 virus.

avian flu virus

According to the aforementioned statement “Of the 1,568 human infections with avian influenza A(H7N9), 33 have reported mutations in the hemagglutinin gene indicating a change to high pathogenicity in poultry. These 33 cases were from Taiwan, China (one case had travel history to Guangdong), Guangxi, Guangdong, Hunan, Shaanxi, Hebei, Henan, Fujian, Yunnan, and Inner Mongolia. No increased transmissibility or virulence of the virus within cases of human infection has been detected related to the H7N9 virus”.

The H9N2 virus has caused no human infection this year, so far. The confirmed cases have been 82, with 2 deaths for underlying conditions, since 2015.

Even the avian flu H10N3 virus has caused no human infection this year, until now. Two cases have been reported globally. The latest dates back to June 2022 and the patient has fully recovered. According to WHO, currently, the H10N3 virus has a low pathogenicity and the likelihood to infect humans remains sporadic at the moment.

By contrast, an awful contagion is spreading among animals, with several avian flu outbreaks reported only at the beginning of 2023.

Avian Flu Outbreaks in Birds

From 20 to 26 January 2023, WHO reported:

1 outbreak of high pathogenic avian influenza H5N2, in Japan, with over 55,000 birds killed;

49 outbreaks of high pathogenic avian flu H5N1 in the city of Izumi, with 171 cases and 171 deaths among wild birds;

5 new outbreaks of high pathogenic avian influenza H5 (N untyped)) in Japan in the following cities; Itoshima, Sapporo, Tottori, Natori, Ichinoseki and Seiro town, with 6 cases and 6 deaths in wild bird species;

5 further outbreaks of high pathogenic avian influenza H5 (N untyped)) always in Japan in the following cities; Miyashiro, Tateyama, Fukuoka, Sapporo, Tottori, Natori, Ichinoseki and the town of Seiro, for a total of 6 cases and 6 deaths in species of wild birds.

Conclusion

The matter of avian flu is still in the making, because the numbers of the contagion could rise or decrease, with a risk of genetic mutations in these viruses or the development of a new variant capable of infecting humans more aggressively.

Unfortunately, the spillover from birds to mammals has already occurred. Even wild birds such as owls have been infected. Only crows seem to be avian flu immune, and this fact is an opportunity to discover how to make humans immune and protected from a likely new pandemic of bird flu.

References and Bibliography

  1. Dr. Calogero Terregino, Director of the national and European reference center for avian flu at the Istituto Zooprofilattico Sperimentale delle Venezie
  2. Dr. Matteo Bassetti, Head of Infectious Diseases of the San Martino Hospital in Genoa
  3. Aviaria, Terregino (IZSVe): “Grande attenzione, ma dopo Covid-19 Italia più preparata a eventuale pandemia” – Isabella Faggiano – Sanità Informazione – February 14, 2023 – https://www.sanitainformazione.it/salute/aviaria-terregino-izsve-litalia-pronta-ad-affrontare-uneventuale-pandemia/
  4. Bird flu continues to spread in mammals – what this means for humans and wildlife –  Divya Venkatesh –  The Conversation –  February 13, 2023 – https://theconversation.com/bird-flu-continues-to-spread-in-mammals-what-this-means-for-humans-and-wildlife-199371
  5. Influenza aviaria, confermata la diffusione tra uccelli e mammiferi. L’Oms: “Prepariamoci a una possibile pandemia”. Bassetti: “Pericolosa, facciamoci trovare pronti” – Michele Martino – La Stampa – February 11,2023 – https://www.lastampa.it/cronaca/2023/02/11/news/influenza_aviaria_dati_allarme_oms_bassetti-12636972/
  6. World Health Organization – Avian Influenza – Weekly Update Number 880 – January 27, 2023 – https://www.who.int/docs/default-source/wpro—documents/emergency/surveillance/avian-influenza/ai_20230127.pdf?sfvrsn=22ea0816_23
  7. Wild owl found with avian flu on ‘Shropshire border with north Staffordshire’ –  David Tooley – Shropshire Star  – February 13, 2023 – https://www.shropshirestar.com/news/health/2023/02/13/wild-owl-found-with-avian-flu-on-shropshire-border-with-north-staffordshire/
  8. Centers for Disease Control and Prevention – What To Know About Bird Flu – https://www.cdc.gov/flu/pdf/avianflu/Bird-Flu-Exposure-Handout.pdf
Author: Rosalba Mancuso
Rosalba Mancuso is a medical journalist, an international content writer credited at the University of Washington and a blogger born in Sicily. She is popular for founding four websites in English. On Modernhealthinfo.com, Rosalba writes well researched and detailed health articles backed by her experience as a medical writer for pharma companies and as a PR assistant for a clinical analysis laboratory. She is also a member of the AHCJ, American Association of Health Care Journalists and Center for Excellence in Health Journalism.

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