- P.Akshay Khumar

Introduction…• It is an enveloped RNA virus from the

Orthomyxovirus family• Influenza viruses are classified based on

antigenic structures on the envelope called neuraminidase “N” and haemagglutinin “H”.

• This illness is referred as "Swine Flu" because the genes of this virus strain were found to be similar to influenza virus occurring in pigs in North America.

Etiology…• Swine flu is contagious, and it spreads in the same

way as the seasonal flu. • When people who have it cough or sneeze, they

spray tiny drops of the virus into the air. If you come in contact with these drops or touch a surface that an infected person has recently touched, you can catch H1N1 swine flu.

• They survive for 2-8 hours after being deposited on the surface

• Despite the name, you can't catch swine flu from eating bacon, ham, or any other pork product.

Genetic reassortment….

• Pigs serves as site of genetic reassortment• Pigs may be simultaneously affected by Swine

and human influenza virus.• Even bird flu from faeces of birds• The virus has segmented RNA and during

replication they may get mixed up• Antigenic Shift

Pathogenisis…

• People in close contact with the pigs acquire the infection

• After inhalation, the virus gets deposited on the surface of the lower respiratory tract

• The estimated incubation period in humans is unknown and more likely 1-4 days

• Patient may be contagious from one day before they develop symptoms to up to 7 days after they get sick.

Contd…• Bronchial and mediastinal lymph nodes get enlarged. • Sharp line of demarcation between normal and affected lung

tissue can be identified with the affected tissue being purple and firm.

• Interlobular edema can be found in few cases.• Airways get filled up with blood-tinged fibrinous exudates

with peribronchial and perivascular cellular infiltration.• Fibrinous pleuritis is seen in severe cases.• Microscopically lesions show airways filled with exudate, with

extensive alveolar atelectasis, interstitial pneumonia and emphysema.

• Research revealed that widespread interstitial pneumonia causes hemorrhagic lymph nodes.

Symptoms….• Most symptoms are the same as seasonal flu. They can include:• cough• fever• sore throat• stuffy or runny nose• body aches• headache• chills• Fatigue• Rashes• Vomitting and diarrhoea

Diagnosis…

• Clinically by History ( Association with people having the above symptoms)

• Nasopharyngeal swab to distinguish type A and B• If Type A, more chances of swine flu• Swine flu is definitively diagnosed by identifying the

particular antigens (surface proteins) associated with the virus type in specialized laboratories by PCR

• CDC recommended only hospitalized patients' flu virus strains be sent to reference labs to be identified

Vaccination…• The best treatment for influenza infections in humans

is prevention by vaccination

Nasal Spray:

The first H1N1 vaccine released in early October 2009 was a nasal spray vaccine that was approved for use in healthy individuals ages 2-49• The nasal spray vaccine contains live virus that have

been altered to hinder its ability to replicate in human tissue. People with a suppressed immune system should not get vaccinated with the nasal spray

The injectable vaccine:• The injectable vaccine, made from killed H1N1,

became available in the second week of Oct. 2009. This vaccine was approved for use in ages 6 months to the elderly, including pregnant females.

• The flu shot (vaccine) is made from killed virus particles so a person cannot get the flu from a flu shot

Intradermal (trivalent) vaccine• A new influenza vaccine preparation is the intradermal (trivalent)

vaccine is available; it works like the shot except the administration is less painful. It is approved for ages 18-64 years.

“Most vaccinies are derived fromEgg culture technique”

Adverse effects of vaccination:• Flu shot: Soreness, redness, minor swelling at the shot site, muscle

aches, low-grade fever, and nausea• Nasal spray: runny nose, low-grade fever, vomiting, headache,

wheezing, cough, and sore throat• Intradermal shot: redness, swelling, pain, headache, muscle aches,

fatigue

Antiviral agents:• Two antiviral agents have been reported to help prevent or

reduce the effects of swine flu. They are zanamivir (Relenza) and oseltamivir (Tamiflu)

• These drugs should not be used indiscriminately, because viral resistance to them can and has occurred.

• Also, they are not recommended if the flu symptoms already have been present for 48 hours or more

• Hospitalized patients may still be treated past the 48-hour guideline.

• Pregnant females can be treated with the two antiviral agents.