Lesson 2: 

#🦠 Influenza

Parajuli SB, 2025
🌐 www.suryaparajuli.com.np
🏥 Community Medicine (Kathmandu University) | MBBS 6th Semester |

#🎯 Specific Learning Outcomes (SLOs)

At the end of the session, the learner will be able to:

🔹 State the “Golden 3” basics of Influenza — the causative agent, mode of transmission, and period of communicability.

🔹 Describe the problem statement and public health importance of seasonal and pandemic influenza.

🔹 Explain the epidemiological determinants of influenza including host, agent, and environmental factors.

🔹 Identify the clinical features, diagnostic approaches, and treatment options for influenza, including use of antivirals.

🔹 Discuss the prevention and control measures, including types of influenza vaccines, their schedules, contraindications, and adverse effects.

🔹 Describe the principles and importance of influenza surveillance in controlling outbreaks and informing vaccine policy.

#🥇 Golden 3 Basics of Influenza

🦠 Influenza is an acute respiratory tract infection caused by the influenza virus, which is classified into four types:

🔹 Influenza A
🔹 Influenza B
🔹 Influenza C
🔹 Influenza D

📌 Important Points

🔹 Influenza A and B are responsible for epidemics in humans.

🔹 The disease is characterized by sudden onset of symptoms such as:

🌡️ Chills
😫 Malaise
🔥 Fever
💪 Muscle pain
😮‍💨 Cough

#🌍 Problem Statement

🌎 Influenza is a global disease, capable of affecting populations worldwide, regardless of geography.

🔄 Pandemics occur every 10–40 years, driven by major antigenic changes in the virus.

📜 Historical Pandemics include:

🗓️ 1918 — Spanish influenza

🗓️ 1957 — Asian influenza

🗓️ 1968 — Hong Kong influenza

📊 Global Burden

🔹 Annual influenza epidemics result in an estimated:

🧑‍⚕️ 3–5 million cases of severe illness

⚰️ 290,000 to 650,000 deaths globally

🦠 Influenza A is the predominant strain, accounting for approximately 59% of all detected influenza viruses worldwide.

#🧬 Types of Influenza

🔹 🌦️ Seasonal Influenza

🔹 🐦 Avian Influenza (Bird Flu)

🔹 🐖 Pandemic Influenza A (Swine Flu)

#🌦️ Seasonal Influenza

#🦠 Epidemiological Determinants – Agent Factors

#(a) 🧪 Agent

🏷️ Family: Orthomyxoviridae

🧬 Types: Four viral subtypes

🔹 Influenza A
🔹 Influenza B
🔹 Influenza C
🔹 Influenza D

🚫 Cross-immunity:
No cross-immunity exists between the types.

#🦠 Key Characteristics

#Influenza A Virus

Has two distinct surface antigens:

🔹 Haemagglutinin (H)
➡️ Enables virus to attach and enter host cells.

🔹 Neuraminidase (N)
➡️ Facilitates release of new viral particles from infected cells.

🧬 Subtypes:
🔹 18 HA
🔹 11 NA

👨‍⚕️ Humans are mostly infected with:

🔹 H1, H2, H3
🔹 N1, N2

#🔄 Antigenic Variation

#🔴 Antigenic Shift

⚡ Sudden, major change

🧬 Due to genetic reassortment
(e.g., human–avian virus mix)

🌍 Leads to pandemics

#🟡 Antigenic Drift

🐢 Gradual change

🧬 Due to point mutations

📈 Leads to seasonal epidemics

#🦠 Influenza B Virus

🔹 Does not undergo antigenic shift

🔹 Not divided into subtypes

🔹 Minor antigenic drift may occur

#🦠 Influenza C Virus

🔹 Antigenically stable

🔹 Causes mild illness

🔹 Does not contribute to epidemics

#🐖🐎🐕 Reservoir of Infection

A major reservoir of influenza viruses exists in animals and birds.

🦠 Influenza viruses have been isolated from:

🐖 Swine

🐎 Horses

🐕 Dogs

🐈 Cats

🐔 Domestic poultry

🦅 Wild birds

#🧫 Source of Infection

The source is usually:

🧑‍⚕️ Clinical case

🤧 Subclinical/asymptomatic case

📌 During epidemics, many mild or asymptomatic infections occur and play a major role in transmission.

🫁 Respiratory tract secretions
(droplets, aerosols) are infective.

#⏳ Period of Infectivity

The virus is present in the nasopharynx:

🗓️ From 1 to 2 days before symptom onset

🗓️ Up to 1 to 2 days after symptom onset

#🧍 Epidemiological Determinants – Host Factors

#(a) 👶 Age and Sex

🔹 Influenza affects all age groups and both sexes.

🔹 Children have a higher attack rate and play a significant role in transmission.

🔹 Adults tend to have a lower attack rate.

#(b) 🌍 Human Mobility

🚶 Movement of people contributes significantly to the spread of infection, especially during outbreaks and epidemics.

#(c) 🛡️ Immunity

🔹 Immunity is subtype-specific
(no cross-protection between types A, B, and C)

🧪 Antibodies against:

🔹 Haemagglutinin (HA)
🔹 Neuraminidase (NA)

are key for protection.

📊 Timeline of antibody response:

🗓️ Appears ~7 days after infection

📈 Peaks in ~2 weeks

📉 Declines to pre-infection level in 8–12 months

#🌍 Epidemiological Determinants – Environmental Factors

#(a) 🌦️ Season

🌍 Northern Hemisphere:
🔹 Epidemics commonly occur during winter months.

🌏 Southern Hemisphere:
🔹 Occurs during winter or rainy season.

🌴 Tropical regions:
🔹 Influenza circulates year-round, with 1 or 2 peaks typically during the rainy season.

#(b) 🏫 Overcrowding

🔹 Facilitates transmission of the virus.

📊 High attack rates observed in densely populated settings, such as:

🏫 Schools

🏠 Hostels

🏢 Institutions

🚢 Ships

🪖 Military camps

#🚶‍♂️ Mode of Transmission

🦠 Influenza primarily spreads from person to person via:

💧 Droplet infection

🌫️ Droplet nuclei

🔹 These droplets are generated when an infected person:

🤧 Sneezes
😮‍💨 Coughs
🗣️ Talks

📍 Portal of entry:
🫁 Respiratory tract

#⏳ Incubation Period

🗓️ Ranges from 1 to 4 days after exposure to the virus.

#🧬 Pathogenesis and Clinical Features

🦠 The virus enters through the respiratory tract, causing:

🔹 Inflammation
🔹 Necrosis of the tracheal and bronchial mucosa

➡️ Followed by secondary bacterial invasion

❌ No viraemia observed

#🤒 Common Symptoms (Influenza A & B)

🌡️ Fever

🥶 Chills

😖 Body aches and pains

😮‍💨 Cough

😫 Generalized weakness

🕒 Fever duration:
🔹 1–5 days
🔹 Average 3 days in adults

#⚠️ Frequent Complications

👃 Acute sinusitis

👂 Otitis media

😤 Purulent bronchitis

🫁 Pneumonia – Most serious complication

#🚨 Suspect Pneumonia If:

🌡️ Fever persists >4–5 days

🔁 Fever recurs abruptly after initial recovery

#🚨 Reye Syndrome (Rare but Severe)

🧠 Encephalopathy with fatty liver (hepatic failure)

🧒 Seen mainly in children aged 2–16 years

💊 Associated with aspirin use during viral infections

☠️ Mortality rate:
🔹 10–40%

❓ Exact pathogenesis unknown

#🐦 Avian Influenza (Bird Flu)

#🌟 Golden 5 Basics of Bird Flu

🐦 Primary Host:
Birds, especially wild waterfowl and domestic poultry.

🔄 Transmission:
Mainly bird-to-bird; rare bird-to-human transmission.

🤒 Symptoms in Humans:
Range from mild flu-like illness to severe respiratory disease.

🌍 Pandemic Risk:
Mutation or reassortment can lead to human-to-human transmission.

🛡️ Prevention:
Surveillance, poultry control, and public health preparedness.

#🐦 Avian Influenza (Bird Flu) (Bird’s EYE View)

🦠 Avian influenza refers to a large group of influenza viruses that primarily infect birds.

🔹 Occasionally, some avian influenza viruses can infect other species such as:

🐖 Pigs
👨 Humans

…but this is rare.

📊 The vast majority of avian influenza viruses do not infect humans.

🦠 The H5N1 strain is notable for its pandemic potential because it might adapt to become contagious among humans.

🔄 When such an adaptation happens:

➡️ The virus transitions from a bird virus to a human influenza virus.

🌍 Influenza pandemics occur when new influenza viruses adapt to human transmission.

👨‍⚕️ Health experts have been closely monitoring the H5N1 virus for almost 15 years due to its severity.

📌 Currently:

🔹 Does not easily jump from birds to humans

🔹 Does not spread efficiently among humans

⚠️ However:

Once a fully contagious virus emerges, its global spread is considered inevitable.

#🔄 Transmission of Avian Influenza

👨 Human infections with avian influenza viruses are rare but sporadically reported.

🦠 Infection usually occurs through direct contact with:

🐔 Infected live or dead poultry birds

OR

🏪 Contaminated environments
(e.g., live bird markets)

#⏳ Incubation Period

🗓️ Typically ranges from 2 to 5 days after exposure.

#🔬 Diagnosis

✅ Confirmed by:

🧪 RT-PCR
(Reverse Transcriptase Polymerase Chain Reaction)

⚠️ Rapid Influenza Diagnostic Tests (RDTs):

🔹 Available
🔹 Have lower sensitivity compared to RT-PCR.

#💊 Treatment

🦠 Antiviral drugs such as:

💊 Oseltamivir

💊 Zanamivir

can:

🔹 Reduce the duration of viral replication

🔹 Improve chances of survival

#🛡️ Prevention

🧼 Regular hand washing with proper drying

😷 Good respiratory hygiene
(cover mouth and nose when coughing or sneezing)

🏠 Early self-isolation if sick

🚫 Avoid close contact with infected individuals

🚫 Avoid touching the eyes, mouth, and nose

#💉 Vaccine

📅 In 2007, a vaccine for bird flu was licensed for people 18 to 64 years old.

💉 It is an inactivated influenza vaccine administered in:

🔹 Two doses
🔹 28 days apart

#⚠️ Common Side Effects

💉 Pain and tenderness at injection site

🤕 Headache

💪 Muscle pain

😫 General malaise

📌 Other vaccines have been approved, but because H5N1 mutates continuously, existing vaccines may not always be effective during a pandemic.

#🐖 Pandemic Influenza A (H1N1) 2009 (Swine Flu)

#🌟 Golden 5 Basics of Pandemic Influenza A (H1N1) 2009

🧬 Origin:
Swine-origin influenza virus with novel genetic makeup.

👥 Population Impact:
Mainly affects children, young and middle-aged adults due to low immunity.

🫁 Pathogenicity:
Ability to infect lower respiratory tract causing severe pneumonia.

🌍 Global Spread:
Rapid worldwide dissemination; declared pandemic in 2009.

📌 Current Status:
Now circulates as a seasonal virus with ongoing surveillance.

#🐖 Pandemic Influenza A (H1N1) 2009 (Swine Flu) (Bird’s EYE View)

🔹 The H1N1 2009 virus differs from seasonal influenza in two key ways:

1️⃣ Low pre-existing immunity in most people led to infection across a wider age range, especially in children and young adults.

2️⃣ The virus can infect the lower respiratory tract, causing rapidly progressive pneumonia, notably in children and young to middle-aged adults.

📅 The virus emerged in March 2009 and spread quickly worldwide.

📅 On 11th June 2009, WHO declared it a pandemic.

🌍 The world is now in the post-pandemic period.

📊 In India, the virus causes local outbreaks; in 2020, India reported:

🔹 2,752 cases
🔹 44 deaths
🔹 Case fatality rate of 1.6%

📌 Based on past pandemics, H1N1 2009 is expected to circulate seasonally for years.

⚠️ Though current concern has diminished, national health vigilance remains critical due to unpredictable virus behavior.

📅 On 26th September 2011, WHO renamed it Influenza A (H1N1) pdm09.

#⏳ Incubation Period

🗓️ Typically 1 to 4 days

📌 Can range up to 7 days

#📋 Case Definitions for Influenza A (H1N1) 2009

#🧑‍⚕️ 1. Suspected Case

A person with acute febrile respiratory illness (fever ≥ 38℃) with onset:

(a) Within 7 days of close contact with a confirmed influenza A (H1N1) 2009 case, or

(b) Within 7 days of travel to areas with confirmed cases, or

(c) Residing in a community with confirmed influenza A (H1N1) 2009 cases.

#🧪 2. Probable Case

A person with acute febrile respiratory illness who:

(1) Tests positive for influenza A, but subtyping for H and N is not possible by RT-PCR or reagents for seasonal influenza, or

(2) Tests positive for influenza A by rapid test or immunofluorescence assay (IFA) and meets suspected case criteria, or

(3) Has a clinically compatible illness and died of unexplained acute respiratory illness epidemiologically linked to a probable or confirmed case.

#✅ 3. Confirmed Case

A person with acute febrile respiratory illness with laboratory confirmation of influenza A (H1N1) 2009 infection by WHO-approved tests:

🔹 Real-Time PCR

🔹 Viral culture

🔹 Four-fold rise in influenza A (H1N1) specific neutralizing antibodies

#🩺 Clinical Features of Influenza A (H1N1) 2009

The disease presents a wide clinical spectrum, ranging from:

🔹 Mild, non-febrile upper respiratory illness

🔹 Febrile influenza-like illness (ILI)

🔹 Severe or fatal complications, including rapidly progressive pneumonia.

📊 Case fatality rate:
Approximately 0.5%, though this may vary.

#🧾 (a) Uncomplicated Influenza

#🤒 Influenza-Like Illness (ILI) Symptoms

🌡️ Fever

😮‍💨 Cough

😣 Sore throat

👃 Rhinorrhoea (runny nose)

🤕 Headache

💪 Muscle pain

😫 Malaise (general discomfort)

🚫 No shortness of breath or dyspnoea (difficulty breathing)

📌 Patients may have some or all of these symptoms.

#🍽️ Gastrointestinal Illness

🔹 Diarrhoea and/or vomiting, especially common in children

🔹 Occurs without evidence of dehydration

#⚠️ (b) Complicated or Severe Influenza

#🩺 Clinical and Radiological Signs

😮‍💨 Shortness of breath (dyspnoea)

💨 Rapid breathing (tachypnea)

🩸 Low oxygen levels (hypoxia)

🫁 Radiological evidence of lower respiratory tract disease (e.g., pneumonia)

🧠 Central nervous system involvement
(e.g., encephalopathy, encephalitis)

💧 Severe dehydration

🦠 Secondary complications such as:

🔹 Renal failure

🔹 Multi-organ failure

🔹 Septic shock

Other complications:

💪 Rhabdomyolysis (muscle breakdown)

❤️ Myocarditis (heart inflammation)

#🏥 Exacerbation of Underlying Chronic Diseases

Includes:

🫁 Asthma

🫁 Chronic Obstructive Pulmonary Disease (COPD)

🧫 Chronic liver or kidney failure

🍬 Diabetes

❤️ Cardiovascular conditions

📌 Any clinical condition requiring hospital admission for management.

⚠️ Presence of signs indicating progressive disease.

#🚨 Signs Requiring Urgent Medical Review

Patients with initially uncomplicated influenza may rapidly (within 24 hours) develop severe illness.

#🫁 (a) Oxygen Impairment or Cardiopulmonary Insufficiency

😮‍💨 Shortness of breath (with activity or at rest)

😰 Difficulty breathing

🔵 Cyanosis (turning blue)

🩸 Bloody or discolored sputum

💔 Chest pain

📉 Low blood pressure

👶 In children: fast or labored breathing

📟 Hypoxia detected by pulse oximetry

#🧠 (b) Central Nervous System (CNS) Complications

🧠 Altered mental status

😴 Unconsciousness or drowsiness

⚠️ Difficulty awakening

⚡ Recurring or persistent seizures (convulsions)

😵 Confusion

💪 Severe weakness or paralysis

#🦠 (c) Sustained Virus Replication or Secondary Bacterial Infection

🌡️ Persistent high fever

⏳ Symptoms lasting beyond 3 days

🧪 Laboratory evidence or clinical signs indicating ongoing viral or bacterial infection

#⚠️ Risk Factors for Severe Disease

The risk factors for severe disease from pandemic influenza A (H1N1) 2009 are similar to those for seasonal influenza complications, including:

👶 Infants and young children, especially those under 2 years

🤰 Pregnant women

🫁 Persons of any age with chronic pulmonary diseases
(e.g., asthma, COPD)

❤️ Persons of any age with chronic cardiac diseases
(e.g., congestive heart failure)

🍬 Persons with metabolic disorders
(e.g., diabetes)

🧫 Persons with:

🔹 Chronic renal or hepatic disease

🔹 Certain neurological conditions
(neuromuscular, neurocognitive, seizure disorders)

🩸 Haemoglobinopathies

🛡️ Immunosuppression
(due to HIV, immunosuppressive medication, malignancy, etc.)

💊 Children on chronic aspirin therapy

👴 Persons aged 65 years and older

⚖️ Individuals who are obese, especially those who are morbidly obese

#🧪 Laboratory Diagnosis of Pandemic Influenza A (H1N1) 2009

#⭐ Importance

🔬 Early and accurate lab diagnosis is crucial for:

✔️ Proper case management
✔️ Infection control
✔️ Antiviral treatment decisions
✔️ Avoiding unnecessary antibiotics

#🧫 Diagnostic Tests

#🧪 RT-PCR (Reverse Transcriptase Polymerase Chain Reaction)

✔️ Most sensitive and timely test for detecting infection.

#⚡ Rapid Influenza Diagnostic Tests (RIDTs)

✔️ Widely available
⚠️ Less sensitive

❗ Negative results do not rule out infection and should not delay treatment or infection control.

#🧴 Specimen Collection

📌 Respiratory samples are required.

#Upper respiratory tract samples:

👃 Nasal swabs

👃 Nasopharyngeal swabs

👄 Throat swabs

#Lower respiratory tract samples:

🫁 Tracheal aspirates

🫁 Bronchial aspirates

✔️ Provide higher diagnostic yield in patients with lower respiratory symptoms.

#🩺 Clinical Diagnosis

📌 When influenza is widespread:

✔️ Uncomplicated cases can be diagnosed clinically and epidemiologically.

#📅 Follow-Up Advice

Patients should be advised to:

🔄 Seek follow-up if symptoms worsen

⏳ Or do not improve within 72 hours

#🎯 Testing Prioritization

Testing should be prioritized for:

⚠️ At-risk groups

⚠️ Severe or progressive illness

📌 Results guide:

✔️ Infection control

✔️ Management of close contacts

#⚠️ Important Note

🚫 Diagnostic testing should never delay:

✔️ Infection control measures

✔️ Initiation of antiviral treatment

If clinical and epidemiological suspicion is high.

#🦠 Infection Control Measures

#🔄 Transmission

Pandemic H1N1 spreads similarly to:

🦠 Seasonal influenza A and B viruses.

#🧼 Standard Precautions

✔️ Practice strict hand hygiene with soap and water or alcohol-based sanitizer.

✔️ Cover mouth and nose with tissue or handkerchief when coughing or sneezing.

✔️ Ill persons should wear a face mask when going out in public
(e.g., to seek medical care) to reduce virus spread.

#🫁 Aerosol-Generating Procedures

Examples:

🔹 Bronchoscopy

🔹 Respiratory tract aspiration

Required protection:

😷 Use particulate respirators
(N95, FFP2, or equivalent)

👓 Wear eye protection

🧥 Wear gown

🧤 Wear gloves

🌬️ Perform procedures in well-ventilated rooms
(natural or mechanical ventilation).

#🏥 Isolation Precautions for Hospitalized Patients

📅 Continue isolation for:

✔️ 7 days after illness onset

OR

✔️ At least 24 hours after fever and respiratory symptoms resolve, whichever is longer.

#⚠️ Special Cases

For prolonged or complicated illness (e.g., pneumonia):

✔️ Maintain precautions until clinical improvement.

🛡️ Immunosuppressed patients require special attention

Because:

🔹 They may shed virus longer

🔹 Higher risk of antiviral resistance

#💉 Influenza Vaccine

There are currently three main technologies used to produce influenza vaccines:

#🥚 Egg-Based Vaccines

✔️ Inactivated influenza vaccines (IIVs)

Prepared from:

🥚 Virus particles grown in embryonated chicken eggs.

Process:

🔬 Virus particles are inactivated

🧪 Detergent-solubilized

➡️ To isolate:

🔹 Haemagglutinin (HA)

🔹 Neuraminidase (NA) proteins

#🌡️ Live Attenuated Influenza Vaccine (LAIV)

✔️ Made from weakened virus strains grown in eggs.

#🧫 Cell-Cultured Vaccines

Produced by:

🧬 Growing influenza viruses in animal cell cultures instead of eggs.

Advantages:

⚡ Faster manufacturing process.

⚠️ Note:

Although no hen's eggs are used, trace amounts of egg protein might still be present.

#🧬 Recombinant Influenza Vaccines

Method:

🔬 Isolates the HA gene and proteins

➡️ Stimulates immune response without using chicken eggs.

Produced in:

🦠 Insect cell cultures.

Feature:

📊 Contain about three times more HA than standard-dose vaccines.

✔️ Recombinant vaccine is the only completely egg-free influenza vaccine.

#🧬 Vaccine Composition

Influenza vaccines include components from:

🦠 Human influenza A viruses

🦠 Influenza B viruses

#📅 Vaccine Update Process

Formulation is reviewed and updated annually based on:

🔹 The viruses currently circulating in the population

🔹 How widely these viruses are spreading

🔹 Effectiveness of the previous year’s vaccine

🌍 The World Health Organization (WHO) provides recommendations on which specific virus strains should be included each year.

#💉 Inactivated Influenza Vaccine (IIVs)

#📘 Overview

📅 Available since the 1940s

#🧬 Trivalent IIVs contain:

🔹 Influenza A (H1N1)

🔹 Influenza A (H3N2)

🔹 One Influenza B strain

#🧬 Quadrivalent Vaccines

📅 Introduced in 2013–2014

✔️ Add:

🔹 A second B strain

➡️ Provide broader protection.

#💉 Administration

📍 Given via:

💉 Intramuscular (IM) injection

💉 Intradermal (ID) injection

#📏 Doses

👶 Pediatric: 0.25 ml

👨 Adult: 0.5 ml

#📅 Dosage Schedule

✔️ One dose annually for persons 9 years and older

👶 Children 6 months to 8 years receiving vaccine for first time:

💉 Two doses

📅 28 days apart

✔️ Annual immunization is recommended.

#💉 Inactivated Influenza Vaccine (IIVs)

#📊 Effectiveness

✔️ Approximately 60% effective among healthy persons under 65 years.

⏳ Protection starts about 14 days after vaccination.

🛡️ Immunity lasts 6–12 months.

⚠️ Vaccinated individuals can still get infected:

🔹 Shortly before vaccination

🔹 Shortly after vaccination

🔹 By influenza strains not covered by the vaccine.

#👴 Effectiveness in Elderly Persons

✔️ 50–60% effective in preventing hospitalization

✔️ 80% effective in preventing death

#📦 Storage

🌡️ Store at 2–8℃

🚫 Do not freeze

#👴 Special Vaccines for Older Adults (65+ years)

Two vaccines designed to improve immune response:

#💉 High-Dose IIV (HD-IIV)

📊 Contains four times the HA antigen of standard vaccines.

#💉 Adjuvanted IIV (aIIV)

🧪 Contains an adjuvant to boost immune response.

✔️ Both are trivalent vaccines.

📊 HD-IIV shown to be 24% more effective than standard vaccines in preventing lab-confirmed influenza in older adults.

#⚠️ Side Effects

#Common Side Effects

💉 Local soreness

💉 Swelling

💉 Redness at injection site

🌡️ Mild fever

💪 Muscle/joint aches

🤕 Headache

⏳ Usually mild and last 1–2 days.

📌 Children tend to have these side effects more often than elderly.

#Rare Side Effects

⚠️ Allergic reactions such as:

🔹 Hives

🔹 Swelling

🔹 Asthma

🔹 Severe systemic hypersensitivity

#🚫 Contraindications — Inactivated Influenza Vaccine (IIVs)

IIVs should NOT be given to:

❌ People with severe allergy to chicken eggs

❌ Those with history of:

🔹 Anaphylactic reaction

🔹 Severe allergic reaction to any vaccine component

❌ Persons who had severe reaction to prior influenza vaccine.

❌ People who developed Guillain-Barré Syndrome (GBS) within 6 weeks after influenza vaccination.

❌ Children under 6 months of age
(vaccine not approved for this age)

❌ People with moderate to severe illness with fever
(vaccination should wait until recovery).

#🌡️ Live Attenuated Influenza Vaccine (LAIV)

#📘 Overview

📅 Approved for use in 2003.

Contains:

🦠 Same influenza viruses as inactivated vaccines

But:

🧬 Cold-adapted to replicate in nasopharyngeal mucosa

#🧪 Production

✔️ Grown in chicken eggs

⚠️ Contains residual egg protein

#💉 Administration

📍 Delivered as:

👃 Single-dose nasal spray

Method:

👃 Half sprayed into each nostril

#🧴 Composition

🚫 Does not contain:

❌ Thimerosal

❌ Other preservatives

#👥 Approved Age Group

✔️ Healthy, non-pregnant persons aged:

📅 2 to 49 years

#🧫 Virus Shedding

👶 Vaccinated children may shed vaccine virus in:

👃 Nasal secretions

⏳ For up to 3 weeks

#📊 Effectiveness of LAIV

✔️ 87% effective against culture-confirmed influenza in children aged 60–84 months.

✔️ Reduces:

👂 Febrile otitis media by 27%

👂 Otitis media requiring antibiotics by 28%

#⚠️ Side Effects — LAIV

#Common Side Effects

👃 Runny nose

👃 Nasal congestion

😮‍💨 Cough

#Less Common Side Effects

😣 Sore throat

🌡️ Low-grade fever

😠 Irritability

💪 Muscle aches

🤕 Headache

#Reported in Some Children

⚠️ Wheezing

⚠️ Vomiting episodes

#🚫 Contraindications — LAIV

LAIV should not be given to:

❌ Children under 2 years

❌ Persons 50 years and older

#❌ Persons with Chronic Medical Conditions

Including:

🫁 Asthma

🌬️ Recent wheezing

🫁 Reactive airway disease

❤️ Chronic pulmonary or cardiovascular diseases

🍬 Metabolic diseases (e.g., diabetes)

🧫 Renal disease

🩸 Hemoglobinopathies
(e.g., sickle cell disease)

#❌ Additional Contraindications

💊 Children/adolescents on long-term aspirin therapy
(due to risk of Reye syndrome)

🛡️ Immunosuppressed persons
(HIV, immunosuppressive therapy)

🤰 Pregnant women

🥚 Persons with severe allergy to eggs

⚠️ Persons with history of Guillain-Barré Syndrome (GBS) within 6 weeks of prior influenza vaccine
(precaution)

📌 Note

Persons in these groups should receive:

💉 Inactivated influenza vaccine instead

#🌍 WHO Recommendations on Influenza Vaccination Priorities

#🏥 Vaccinate Health Care Workers First

Purpose:

✔️ Protect health infrastructure

✔️ Prevent hospital outbreaks

#👥 Recommended Groups by Priority

🤰 Pregnant women

🧫 Individuals >6 months old with chronic medical conditions

🧑 Healthy young adults (15–49 years)

👶 Healthy children

👨 Healthy adults (49–65 years)

👴 Healthy adults >65 years

#💉 COVID-19 Vaccine Interaction

⏳ Wait at least 7 days between:

💉 COVID-19 vaccine

AND

💉 Influenza vaccine

#💊 Treatment of Pandemic Influenza A (H,N) 2009

#🧾 Key Principles of Clinical Management:

✔️ Provide basic symptomatic care (e.g., fever and pain relief).

🧬 Use antiviral drugs early, especially for high-risk populations.

🦠 Administer antimicrobials to treat or prevent co-infections.

📊 Maintain proactive monitoring for signs of disease progression.

#🏥 Hospital Care:

🫁 Early supplemental oxygen therapy to correct hypoxemia, with continuous monitoring of oxygen saturation during triage and hospitalization, if possible.

💧 Careful fluid replacement to maintain hydration.

💊 Use of antimicrobials for other infections causing severe respiratory distress.

🫁 Severely ill patients may require mechanical ventilation and intensive care support due to respiratory distress.

#🧬 Antiviral Therapy for Pandemic Influenza A (H,N) 2009

#🦠 Virus Susceptibility:

#✔️ Susceptible to neuraminidase inhibitors (NAIs):

💊 Oseltamivir

💊 Zanamivir

#❌ Resistant to M2 inhibitors:

🚫 Amantadine

🚫 Rimantadine

#💊 Antiviral Therapy — Treatment Recommendations

#🚨 Severe or Progressive Illness:

✔️ Treat all patients with oseltamivir as soon as possible

📌 Includes:

🤰 Pregnant women

👶 Children under 2 years (including neonates)

#⚠️ If Severe Illness Not Responding:

Consider:

💊 Higher doses (e.g., 150 mg twice daily in adults)

⏳ Longer treatment duration

#🔄 If Oseltamivir Unavailable or Resistant Virus:

💊 Use zanamivir

#🧑‍⚕️ High-Risk Patients with Uncomplicated Illness:

✔️ Treat early with:

💊 Oseltamivir OR
💊 Zanamivir

#🧍 Patients Not at High Risk with Uncomplicated Illness:

🚫 Antiviral treatment is generally not necessary.

✔️ If used, start early for best outcomes.

#⚠️ Additional Notes on Antivirals

📌 Start antiviral treatment immediately based on clinical suspicion

🚫 Do NOT wait for laboratory confirmation

#🔁 If Persistent Severe Illness Despite Oseltamivir:

Alternative options (with caution):

💉 Intravenous zanamivir

💉 Peramivir

💊 Ribavirin
⚠️ Should NOT be used alone and NOT in pregnant women

⚠️ Zanamivir powder for inhalation should NOT be nebulized due to lactose content affecting ventilator function.

#💉 Standard Oseltamivir Antiviral Treatment Regimens

#👶 Infants (<1 year)

#👧 Children (1–12 years by weight)

#🧑 Adults

💊 75 mg orally

🔁 Twice daily

⏳ 5 days

#🧪 Zanamivir Dosing for Influenza Treatment

📌 Indication: Treatment of influenza in adults and children aged ≥5 years

💨 Route: Inhalation (Diskhaler)

#💊 Recommended Dose:

🧑 Adults & children (≥5 years):

💨 2 inhalations (2 × 5 mg = 10 mg)

🔁 Twice daily (morning and evening)

⏳ Duration: 5 days

#🛡️ Chemoprophylaxis Regimen with Oseltamivir

📌 Indication:

✔️ Healthcare personnel
✔️ Close contacts of suspected, probable, or confirmed cases

⏳ Duration:

🗓️ Once daily for 10 days after last exposure

#👶 Infants (<1 year)

#👧 Children ≥1 year (by weight)

#📊 Influenza Surveillance

#🎯 Purpose of Surveillance:

#🧬 Monitor Circulating Strains

📊 Track prevalence and types of influenza viruses in circulation

🧬 Detect emergence of new or variant strains important for vaccine formulation

#📈 Estimate Impact

📊 Assess burden of disease in terms of:

🧑‍⚕️ Morbidity (illness rates)

⚰️ Mortality (death rates)

💰 Economic losses (healthcare costs, lost productivity)

#🚨 Early Outbreak Detection

⚠️ Identify and respond promptly to influenza outbreaks

#🛡️ Guide Control Measures

📌 Enable timely public health action including:

💉 Vaccination campaigns

💊 Antiviral distribution

📢 Public advisories

#🔑 Key Takeaways

🦠 Influenza is a contagious respiratory virus with seasonal and pandemic forms.

💧 Transmission is via droplets and contact; incubation is 1–4 days.

🤒 Symptoms include fever, cough, sore throat; severe disease in high-risk groups.

💊 Treatment includes supportive care and antivirals (oseltamivir/zanamivir).

💉 Vaccination (IIV/LAIV) is key prevention; annual doses recommended.

🛡️ Chemoprophylaxis for exposed high-risk individuals and healthcare workers.

📊 Surveillance tracks virus trends and informs vaccine updates.

#📚 References

1. WHO. Weekly Epidemiological Record, No. 47, 23 Nov 2012.

2. Papadakis MA, McPhee SJ. Current Medical Diagnosis and Treatment, 53rd ed. 2014. Lange Publication.

3. WHO. Fact Sheet, March 14, 2018.

4. WHO. Technical Report Series, No. 642, 1980.

5. WHO. Bulletin of the World Health Organization, 1985; 63(1): 51.

6. Jawetz E, et al. Medical Microbiology, 22nd ed. Lange Medical Publication, 2001.

7. Jawetz E, et al. Medical Microbiology, 28th ed. Lange Medical Publication, 2019.

8. WHO. Weekly Epidemiological Record, No. 49/50, Oct 14, 2005.

9. WHO. Weekly Epidemiological Record, No. 41, 9 Oct 2009.

10. Government of India. National Health Profile 2021. Central Bureau of Health Intelligence, Ministry of Health and Family Welfare, New Delhi.

11. WHO. Recommendations for the Post-Pandemic Period: Pandemic (H1N1) 2009 Briefing Note 23, 2010.

12. WHO. Weekly Epidemiological Record, No. 43, 21 Oct 2011.

13. Government of India. Guidelines for Swine Flu (Influenza A H1N1). Ministry of Health and Family Welfare, New Delhi, 2010.

14. WHO. Clinical Management of Human Infection with Pandemic (H1N1) 2009: Revised Guidance, November 2009.

15. McPhee SJ, et al. Current Medical Diagnosis and Treatment, 49th ed. Lange Medical Publication, 2010.

16. Carter A. Flu Vaccine. Medically reviewed, 8 Sept 2020.

17. Yung AD, et al. U.S. Pharmacist: The Pharmacist Resource for Clinical Excellence, Nov 12, 2019; 44(11): 18–22.

18. CDC. Epidemiology and Prevention of Vaccine-Preventable Diseases, April 15, 2019.

19. WHO. Safety of Pandemic (H1N1) 2009 Vaccines, Oct 30, 2009.