Bird flu, also known as avian influenza, is a viral disease originating from birds. When passed onto humans, this disease can be fatal. As the occurrence of bird flu is not common and symptoms of this disease often overlap with other viral diseases, including seasonal flu, it can be difficult to identify whether a patient has it. Luckily, many different diagnostic methods can be performed on patients to ensure they get the help. 

Overview of bird flu

What is Bird Flu?

Bird flu is a viral disease that can cause great harm to birds. This disease spreads between wild birds and can quickly spread globally once birds begin to migrate. In the UK, almost 80 species of birds have been tested positive for bird flu, including many gulls, ducks and geese. 

Whilst bird flu originates from birds, the virus can spread to humans and cause fatal consequences. Diseases that originate from animals can be described as Zoonotic diseases. Examples of zoonotic diseases include bird flu, rabies and Lyme disease. 

Contact with wild or dead birds can greatly increase a person's risk of getting bird flu. It has been reported that between 2003 and 2023, 876 cases of bird flu were reported in humans, with over half the cases resulting in death.¹ Therefore, it is highly important to accurately diagnose bird flu to prevent outbreaks.

What are the symptoms of bird flu?

The symptoms of bird flu tend to overlap with other types of flu, including seasonal flu. These symptoms include: 

• Cough or sore throat
• Fever
• Headache
• Vomiting
• Diarrhoea
• Irritable eyes

As the symptoms of bird flu often overlap with other viral diseases, this can make it difficult to diagnose bird flu immediately. As the virus continues to attack our bodies, these general symptoms can escalate quickly and become life-threatening. If hospitalised, patients with bird flu will be treated in isolation as the virus can spread very quickly between humans. Such symptoms include: 

• Multiple organ failure - patients may require temporary life support to overcome failure of organ function
• Brain dysfunction - can include being in a state of confusion, having balance problems, having memory loss, having frequent headaches, experiencing hallucinations or personality changes. There are specific types of brain dysfunction depending on the origin. For individuals afflicted by bird flu, the damage to the brain occurs after infection
• Poor lung function - As the virus resides in the respiratory system, many patients will experience breathing difficulties. These individuals may be given oxygen masks to help them breathe

Diagnostic methods for bird flu

There are several ways to diagnose bird flu in the hospital. Depending on the facilities available in the hospital, different tests will be conducted on the patient. 

Taking the history of the patient’s movements is very important in identifying if they are afflicted with bird flu or other types of flu. Contact with sick individuals, dead or ill birds, visits to farms or abroad to high-risk areas are common questions patients will be asked when admitted to the hospital. In addition, a series of laboratory tests can be performed: 

Rapid antigen testing 

You may be familiar with these rapid diagnostic tests following the COVID-19 pandemic. Throat or nose swabs are used to collect samples from the patients’ bodies. These areas are used as they are easily accessible and are usually where the virus resides. 

The test strip is covered in small molecules (antibodies) that can stick to specific molecules the virus has (antigens) - similar to how Velcro sticks together. If the virus is present in the patient sample, it will stick to the test strip, and a positive coloured result will show. This is similar to how pregnancy tests work. Whilst uncomfortable, these rapid antigen tests can help to quickly identify which individuals are infected and the appropriate safety precautions implemented, e.g quarantine, medications. 

Despite their quick results, these antigen tests are not always accurate and can give false positives. This can put unnecessary stress on an individual. To overcome these inaccuracies, it has been suggested that using phlegm (mucus) samples to test for bird flu would be more appropriate¹ as these samples can target the lower respiratory tract where the virus tends to reside.  

Polymerase chain reaction (PCR test)

PCR tests are performed at laboratories and use special machines to try and amplify patient samples. If hospitalised, the patient sample will be given to the hospital laboratory, which has its testing facilities.

PCR can quantify the amount of virus in a sample. If the amount of virus in a sample exceeds a certain threshold, then the patient is likely to be infected with the disease.

Because of their high sensitivity and specificity to viral molecules, these tests are used as the gold standard to diagnose and monitor the spread of bird flu. These tests are also useful to identify specific genes that make up the virus. These results can be used to track if there are any variants of the virus. Identifying different strains of the virus can help develop vaccines against the disease.

However, performing PCR requires specialist training, and the machines themselves are expensive. Some hospitals may not have the appropriate facilities to perform diagnostic tests. In the UK, most major cities will have a dedicated Virology department that is equipped with the appropriate facilities to diagnose many diseases, including bird flu. 

Blood tests 

Blood tests can be taken from patients to identify if specific proteins from the virus are present in the sample. These proteins are specific and are only produced when the bird flu is present. Whilst taking blood tests gives accurate results, processing of blood tests can take several days as it takes time for our body to react to the virus and produce these proteins. Therefore, it is unlikely that blood tests will be taken in the clinic to diagnose bird flu. A group of researchers have developed a way to obtain results quickly from blood tests with a high sensitivity.² This research could be very useful in areas that do not have access to PCR machines. 

Whole body diagnosis 

As well as the laboratory tests described above, a diagnosis of bird flu will be made in combination with a physical examination. An ECG may be taken to assess the function of the heart, x-rays of the chest to assess lung function, and an MRI may be performed to assess brain function. These tests are important to assess how ill the patient is and if they are at risk of multiple organ failure and will require more specialist treatment. 

Summary

Bird flu is a highly dangerous disease that can spread from birds to humans. Symptoms of bird flu are very uncomfortable and can escalate very quickly. If not diagnosed correctly, it can result in the death of patients. In the clinic, many different tests can be performed on the patient to accurately diagnose bird flu. Patients will often be treated in isolation from other patients to prevent the spread of infection to other people. Through accurate diagnosis, the spread of bird flu and the risk of a pandemic can be minimised.