Avian Influenza: Causes, Symptom and Treatment

Introduction

Avian influenza, or bird flu, is a viral infection that mostly affects birds but can infect humans and some other animals too.

This disease is caused by influenza A viruses, which are categorized into subtypes based on two proteins on the virus’s surface: hemagglutinin (H) and neuraminidase (N).

Most avian influenza viruses are found in birds, but certain strains can infect humans and other species, sometimes leading to serious health issues or outbreaks.

The most important strain for humans is H5N1, which has led to multiple serious human illnesses since it appeared in the late 1990s. Avian influenza is still a health concern because of its ability to mutate, which could lead to greater spread among humans.

Causes

Avian influenza happens due to the influenza A virus, which has various subtypes classified by the hemagglutinin (H) and neuraminidase (N) proteins present.

Although there are many avian influenza subtypes, only a few have been linked to human infections.

The most recognized subtypes that can infect humans include:

1. H5N1: This strain has caused severe cases of avian influenza in people, with a high death rate. H5N1 mostly circulates in wild birds and domestic chickens, with humans getting infected often through direct contact with sick birds or surfaces they contaminated.
2. H7N9: This subtype raises significant health concerns, especially in China, as H7N9 infections are mostly associated with poultry exposure and may lead to serious respiratory problems.
3. H9N2: Though less linked to human illness, H9N2 infections have occurred, particularly in people closely interacting with poultry. This strain usually results in mild illness but could mutate for human-to-human spread.

The virus mainly spreads through contact with infected birds and their saliva, feces, or nasal fluids.

It may also spread via contaminated feed, water, or tools for handling poultry.

The virus can survive in the environment for a certain time, particularly in cooler weather, and can infect humans close to sick birds or their droppings.

Symptoms

Symptoms of avian influenza in humans can vary from mild to serious, based on the virus subtype and the person’s health.

Many infected individuals will have flu-like symptoms, while others could face serious conditions like respiratory issues and pneumonia.

Common signs of avian influenza in humans include:

• Fever: Often a high fever with chills occurs early on.
• Coughing: A dry or wet cough may develop and be associated with breathing difficulties.
• Sore Throat: Many report a sore throat initially.
• Muscle Aches and Fatigue: Similar to seasonal flu, aches and fatigue are frequent.
• Headache: Headaches can be severe and worsen with the illness.
• Shortness of Breath: Patients might struggle to breathe and feel chest tightness, particularly in severe cases.
• Gastrointestinal Symptoms: Some might experience nausea, vomiting, diarrhea, and stomach pain, especially children or those seriously ill.
• Conjunctivitis (Eye Infection): Rarely, avian influenza can lead to eye infections. or conjunctivitis, but this is rarer.

In severe situations, especially with H5N1 and H7N9 types, the virus can quickly progress to pneumonia, acute respiratory distress syndrome (ARDS), and multi-organ failure, which might be deadly.

The death rate can vary greatly based on the subtype and any existing health issues.

Risk Factors

Multiple factors can raise the chance of getting avian influenza and developing serious illness:

• Close Contact with Poultry: Those working with poultry, like farmers, slaughterhouse laborers, and vets, are at the greatest risk. Close interaction with sick birds or their droppings is a key way the virus spreads.
• Handling Infected Birds: Individuals who manage or process poultry that is affected by avian influenza are at risk, especially in regions where outbreaks occur.
• Eating Infected Poultry: While avian influenza usually does not spread through cooked poultry, eating raw or undercooked poultry from infected birds can be risky. The virus spreads mainly through direct contact with sick birds.
• Travel to Affected Regions: People who visit places with avian influenza outbreaks, particularly in areas with a lot of poultry farming, are at greater risk of coming into contact with the virus.
• Weak Immune System: Those with weakened immune systems, like HIV/AIDS patients, cancer patients, and those receiving immunosuppressive treatments (such as organ transplant patients), are more likely to face severe disease.
• Age: While anyone can get avian influenza, children and older adults are at a higher risk of serious illness due to their more vulnerable immune systems.
• Pre-existing Respiratory Conditions: Individuals with chronic respiratory issues, such as asthma, chronic obstructive pulmonary disease (COPD), or pulmonary fibrosis, may face more severe symptoms and complications if infected with avian influenza.

Differential Diagnosis

Several respiratory illnesses have symptoms similar to avian influenza, making it crucial to tell them apart.

These include:

• Seasonal Influenza (Flu): Seasonal flu shares many symptoms with avian influenza, including fever, cough, sore throat, and muscle aches. However, avian influenza can be more severe, leading to quicker progression to pneumonia, ARDS, or multi-organ failure, especially in those at risk.
• Pneumonia: Pneumonia, which can arise from various bacterial, viral, or fungal infections, can show similar symptoms to avian influenza, like fever, cough, and trouble breathing. A detailed examination and testing, including chest scans and cultures, are needed to distinguish them.
• Severe Acute Respiratory Syndrome (SARS): SARS, caused by a specific coronavirus, has several similar symptoms to avian influenza, such as fever, cough, and breathing issues. However, SARS outbreaks mainly took place in the early 2000s and had different epidemiological contexts.
• Middle East Respiratory Syndrome (MERS): MERS, caused by another coronavirus, shares symptoms with avian influenza, like fever, cough, and shortness of breath. MERS is linked to contact with camels in certain areas.
• Common Cold or Upper Respiratory Infections: Milder respiratory infections like the common cold may also show fever, cough, and sore throat, but symptoms are usually less severe, and they do not progress to serious pneumonia or respiratory failure, setting them apart from avian influenza.

Investigation

Diagnosing avian influenza includes clinical assessment, travel history (like recent travel or poultry exposure), and lab tests.

1. RT-PCR Testing: Reverse transcription-polymerase chain reaction (RT-PCR) is the main method for confirming avian influenza. in humans. RT-PCR sees viral RNA and finds the specific type of influenza virus, like H5N1 or H7N9. Samples usually come from the respiratory area, including throat and nasal swabs.
2. Viral Culture: Though not as common now because RT-PCR is available, viral culture can confirm the virus’s presence. This method grows the virus from a sample in a lab, but it can take several days to get results.
3. Serology: Blood tests that look for antibodies against the avian influenza virus can show past infections, but they are not used for early diagnosis. Serological tests are better for studying how common the infection is.
4. Chest X-ray: A chest X-ray can find signs of pneumonia, which is often seen in severe cases of avian influenza. Sometimes, a CT scan is needed for clearer images.
5. Blood Tests: Blood tests can check general health, spot complications like organ failure, and assess vital organ function. Issues with liver or kidney function may indicate more severe disease.

Treatment

The treatment for avian influenza in humans is about antiviral medications, supportive care, and infection control. Early finding and treatment are very important for better results.

1. Antiviral Medications:

Oseltamivir (Tamiflu) and Zanamivir (Relenza): These drugs are neuraminidase inhibitors that stop the virus’s spread in the respiratory area. They work best when started early, usually within 48 hours of symptoms.

Baloxavir Marboxil (Xofluza): A newer antiviral that stops virus replication, it’s shown to work against various influenza viruses, including avian types.

2. Supportive Therapy:

Those with severe avian influenza may need hospital care, where they can receive oxygen therapy, mechanical ventilation, and intensive care. Monitoring and managing organ function are crucial in serious cases.

3. Antibiotics:

If secondary bacterial infections, like pneumonia, happen in avian influenza cases, antibiotics may be given to prevent or treat them.

4. Infection Control:

Stopping the spread of avian influenza is vital. Isolating infected people and using personal protective equipment (PPE) are necessary in healthcare settings. Contact tracing, quarantine, and public health actions to manage outbreaks are important.

5. Vaccination:

There is no specific vaccine for avian influenza strains like H5N1 or H7N9, but research continues. Vaccines for seasonal influenza might provide some cross-protection against certain avian influenza strains, though effectiveness may vary.

Prognosis

The outlook for people infected with avian influenza depends on aspects such as the virus subtype, the timing of treatment, and the person’s overall health.

Early antiviral treatment helps survival rates, but mortality for some strains, such as H5N1, can be high, especially in severe cases that end in ARDS and organ failure.

Global health groups keep a watch on avian influenza outbreaks to stop possible pandemics, as the virus can change and adapt to human-to-human spread.

Conclusion

Avian influenza is a serious viral illness mostly affecting birds but can also infect humans and other animals. The risk to humans stays relatively low, yet specific strains, like H5N1 and H7N9, have led to serious illness and death.

Timely diagnosis and antiviral treatment are vital for better outcomes. Preventative steps, such as protecting poultry, monitoring, and vaccine research, are crucial for controlling the disease’s spread.

Watching and quickly responding to outbreaks are essential to reduce the risk of an avian influenza pandemic.