Bird Flu

Dr. Nabi Darya Vali (AIIMS)MBBS

November 28, 2018

January 07, 2021

Bird Flu
Bird Flu

Bird flu, medically known as avian influenza, is a rare infection in humans. It is caused by the highly pathogenic avian influenza type A virus. As the name suggests, it is a viral infection which causes severe respiratory disease in birds. According to the US Centers for Disease Control and Prevention (CDC), influenza viruses occur naturally in wild aquatic birds, who can then spread the virus to domesticated birds and other animal species. Usually, these viruses infect the intestines and lungs of wild birds but do not sicken them.

However, in the case of influenza strains like H5N1, H7N9 and H5N8, the virus can not only cause sickness but is also extremely contagious and potentially fatal. The World Health Organization (WHO) says that some strains of bird flu, like H5N1, are occasionally transmitted to humans and leads to outbreaks among humans too. An infected human presents with several flu-like symptoms and requires treatment. 

In India, less than four thousand cases of bird flu are seen yearly. Here is everything you need to know about bird flu in humans and its potential dangers, symptoms and treatment.

How does the bird flu spread to humans?

The CDC says that birds infected with avian influenza A viruses, especially the highly pathogenic influenza A (HPAI) strains, shed the virus through their saliva, nasal secretions and feces. Coming into contact with these secretions or being in close contact with infected live or dead birds can transmit the virus from birds to humans. Close contact with poultry farms, slaughterhouses and other potentially contaminated environments can also lead to humans becoming infected.

The WHO says that the bird flu virus does not infect humans easily, and human-to-human transmission is very rare. Direct transmission from infected birds is the major source of spread. Further, research clearly shows that there is no evidence that bird flu spreads to humans through properly and thoroughly cooked food, which also reduces the risk of transmission to humans to a large degree.

(Read more: World’s deadliest viral infections)

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What are the main signs and symptoms of bird flu?

The symptoms of bird flu are similar to those of influenza. This may also lead to delayed diagnosis of bird flu and even misdiagnosis in some cases. The following are some common symptoms of bird flu that you should look out for:

Occasionally, people may also experience nausea and vomiting. Alternatively, patients may only have an eye infection, without any other symptoms. If the infection is severe or the patient is compromised due to underlying conditions then bird flu can quickly progress to severe respiratory illnesses like pneumonia and acute respiratory distress syndrome (ARDS). The WHO says that severe H5N1 infection can also cause brain damage and neurological changes, leading to confusion, altered mental status and seizures. These additional symptoms and complications of bird flu also indicate that the progression of this viral infection may be similar to COVID-19 infection.

(Read more: How to tell the difference between COVID-19 and flu?)

What causes bird flu?

There are two main types of the bird flu viruses, the most common type in humans being H5N1.The CDC says that H7N9 virus is the other strain most responsible for human cases of bird flu, especially for outbreaks in Asian countries. Both H5N1 and H7N9 strains can cause serious illnesses and the highest mortality among humans, which the WHO says is likely to be as high as 60%.

In humans, the infection is mainly transmitted through birds by one of the following ways:

  • Inhaling contaminated aerosols from open-air markets selling bird eggs and poultry
  • Touching infected birds
  • Bathing in water containing droppings of infected birds
  • Consuming undercooked meat and eggs from infected birds

It’s important to note that eating thoroughly-cooked meat or eggs is considered safe for humans. The infection is not commonly known to spread from one person to another.

(Read more: Egg whites or yolks, which is healthier?)

How is bird flu diagnosed?

Bird flu cannot be diagnosed by taking an account of the clinical signs and symptoms alone, more so because the symptoms are similar to most other viral infections in humans. Diagnosis of the infection can be done through general lab investigations since the specific test for bird flu is not commonly available at all places.

  • Investigation of fluid samples from nose and throat helps check for the virus.
  • A complete blood count will confirm the presence of an infection in the body.
  • An X-ray of the chest is done to check the health of the lungs.

The CDC says that testing for antibodies in people who are suspected to have had bird flu can also be effective in compiling a thorough account of how many people were infected during a particular outbreak. 

(Read more: Immune system and immunity)

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How is bird flu treated?

Since bird flu in humans can develop into a serious disease quickly, the WHO recommends that any individual diagnosed with the infection should be promptly treated, preferably in a hospital. This is also because the patients may require intensive care and respiratory support during the course of the disease. As a preventive measure, all members of a patient’s family are screened for the virus and advised to stay away from environments that can expose them to the infection. In some cases, the patient may be placed in isolation to eliminate any chances of spreading the infection.

(Read more: Weak immune system)

Standard treatment for bird flu involves antiviral medications. Medications like oseltamivir may reduce the severity of the disease. It is important that the medicine be taken within the first 48 hours of the appearance of symptoms. The CDC also says that antiviral drugs like peramivir and zanamivir may also be effective against H5N1 and H7N9. However, these virus strains seen in humans are known to develop resistance to the most common antiviral medications, hence alternative drugs may have to be prescribed. Healthcare and pharmaceutical systems from around the world are monitoring the cases of antiviral resistance for bird flu drugs closely.

(Read more: How to increase immunity)

Is there a vaccine for bird flu?

The WHO says that although some vaccine candidates for the H5N1 strain of bird flu have been developed, they are not ready for widespread use. The US Food and Drug Administration (FDA), on the other hand, reports that an inactivated influenza virus vaccine, based on the A/Vietnam/1203/2004 H5N1 virus strain, had been licenced in 2007. The vaccine is manufactured by Sanofi Pasteur Inc of Pennsylvania and purchased by the FDA for deployment in case of a rapid outbreak of the virus from human to human (which is said to be rare and unlikely).

However, it’s important to note that the efficacy of this vaccine is not known and neither is its usability. So, effectively, one could say that there is no vaccine available for the bird flu yet. 

(Read more: How are vaccines made?)

What are the risk factors for bird flu?

The transmission of bird flu to humans is possible through close contact with infected birds, contaminated surfaces and environments and consuming undercooked meat or eggs of infected birds. The highest risks of contracting bird flu are faced by: 

  • Poultry farmers
  • Those who are exposed to infected birds
  • People who eat rare or undercooked poultry or eggs
  • Healthcare workers treating or attending to infected patients
  • Household members or close contacts of infected persons
  • Travellers visiting areas with outbreaks of bird flu

(Read more: Common cold)

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How to prevent bird flu?

The best way to prevent bird flu is to avoid all sources of exposure, especially during an outbreak in your area. The following are some of the best ways to prevent bird flu:

  • Prevent exposure to areas or environments where infected birds may be present, including poultry farms, open markets or mandis where poultry is sold and slaughterhouses.
  • Most viruses die when exposed to heat for long durations. Cook your meat and eggs properly, which means cooking it thoroughly, at medium to high temperatures, for an appropriate amount of time.
  • Wash your hands while handling any poultry or produce sourced from open markets where poultry products are sold. Following proper hand and respiratory hygiene is one of the best ways of preventing all types of viral infections.

(Read more: COVID-19 prevention tips for young and healthy people)


  1. Direct (Elsevier) [Internet]; CTL epitopes for influenza A including the H5N1 bird flu; genome-, pathogen-, and HLA-wide screening
  2. Ron A. M et al. Avian influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome. Proceedings of the National Academy of Sciences Feb 2004, 101 (5) 1356-1361
  3. Looi FY et al. Creating Disease Resistant Chickens: A Viable Solution to Avian Influenza?. Viruses. 2018 Oct 15;10(10). pii: E561.PMID: 30326625
  4. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; Information on Avian Influenza
  5. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; Avian Influenza in Birds

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