SWINE INFLUENZA – AND-HIV Prof. P.K. Jain MD,MNAMS Professor & Head, Department of Medicine, M.L.B. Medical College, Jhansi, UP
WHAT IS SWINE INFLUENZA? On the morning of 24 th April 2009, we woke up to the breaking news that WHO had issued an alert on influenza like illness by Swine influenza A (H1N1) virus. Swine influenza or “Swine flu”, is a highly contagious acute respiratory disease of pigs. Caused by one of several swine influenza A viruses. Although the viruses are species specific and only infect pigs, they do sometimes cross the species barrier to cause disease in humans. Morbidity tends to be high and mortality low (1-4%)
EPIDEMIOLOGY The disease is considered endemic in the United States. Outbreaks are also known to have occurred in North and South America, Europe, Africa (Kenya), Mexico and in parts of Asia. Notable outbreaks:- 1918 - pandemic in humans 1976 - U.S. outbreak 1988 zoonosis – there was no community outbreak 1998 - US outbreak in swine 2007 - Philippine outbreak in swine 2009 - outbreak in humans
Severely effected, with maximum deaths Less severely effected
In India till today, 959 cases have been reported of which 7 have died. Maximum cases have been reported from Pune(Maharashtra), Gujarat & Tamilnadu. The first fatality was a 14 year old girl from Pune. She had come in contact with 40 students who travelled from NASA in the US to Pune and though she had not travelled hereself, she got the infection from them.
5 1 1 Fatalities because of Swine flu Pune - 4 Mumbai - 1 Chennai - 1 Ahmedabad - 1
In U.P. till now 1 case of Swine flu has been confirmed in Lucknow. Danik Jagran, Jhansi has reported today one suspected case of Swine flu in Mauranipur whose samples have been sent to SGPGI, Lucknow for confirmation although CMS Jhansi does not think this case clinically as a case of Swine flu.
THE VIRUS The 2009 swine flu outbreak in humans is due to an apparently virulent new strain of influenza A virus subtype H1N1, produced by reassortment from one strain of human influenza virus, one strain of avian influenza virus and two separate strains of swine influenza. This virus was originally referred to as swine flu but the WHO decided to rename it as Influenza A H1N1 virus on 30 th April 2009 in order to avoid confusion over the danger posed by pigs, especially pork consumption, by which the disease is not known to occur. This was also to avoid unnecessary slaughter of pigs.
COMMUNICABILITY OF THE VIRUS A patient is infectious to others from 1 day before the symptoms to 7 days after the onset of symptoms. Children are likely to spread the virus for a longer period. H1N1 appears to be more contagious than seasonal Influenza. The secondary attack rate of seasonal Influenza ranges from 5 to 15% current estimates of the secondary attack rate of H1N1 range from 22 to 33%.
Electron microscope image of the reassorted H1N1 virus. The viruses are 80-120 nanometers in diameter.
Every two or three years the virus undergoes minor changes, but at intervals of roughly a deeade, after the bulk of the world’s population has developed some level of resistance to these minor changes, it undergoes a major change that enables it to easily infect populations around the world, after infecting hundreds of millions of people whose antibody defenses are unable to resist it.
The various types of influenza viruses in humans, Solid squares show the appearance of a new strain, causing recurring influenza pandemics. Broken lines indicate uncertain strain identifications.
TRANSMISSION Pig to Pig- Through direct contact - between infected and uninfected animal. Air borne transmission - through the aerosols produced by pigs coughing or sneezing. Spreads quickly through a herd, infecting all the pigs within a few days.
Swine can be infected by both avian and human influenza strain of influenza, and therefore are hosts where the antigenic shifts can occur that create new influenza strains.
Pig to Human- People who work with poultry and swine, especially people with intense exposures are at increased risk. Transmission to human usually does not result in influenza in human, when it does result in influenza, usually the influenza is mild and an outbreak does not occur. Swine influenza is not caused by eating properly prepared pork meat as the swine influenza virus is killed by cooking at temp. 70 0 C.
Human to Human – Limited to close contacts and closed groups of people. If a swine virus established efficient human to human transmission, it can cause an influenza pandemic. The impact of a pandemic caused by such a virus is difficult to predict: It depends on- virulence of the virus, existing immunity among people, cross protection by antibodies acquired from seasonal influenza infection host factor Swine influenza viruses can give rise to a hybrid virus by mixing with a human influenza virus and can cause pandemic.
SIGNS AND SYMPTOMS In Swine – In pigs influenza infection produces fever, lethargy, sneezing, coughing, difficult breathing and decreased appetite. In some cases the infection can cause abortion. Although mortality is usually low (around 1-4%) the virus can produce weight loss and poor growth.
In Humans – According to the centers for disease control and prevention (CDC), in humans the symptoms of the 2009 “swine flu” H1N1 virus are similar to those of influenza and of influenza-like illness in general. After an incubation period of 18-72 hours, systemic symptoms ensue. .
Symptoms include :- Fever Cough Sore throat Body aches Headache Chills and fatigue. People with underlying chronic conditions, such as cardiovascular diseases, hypertension, asthma, diabetes, rheumatoid arthritis and several others, are more likely to experience severe or lethal infections.
DIAGNOSIS During the 2009 swine flu outbreak in the United States, CDC advised physicians to consider swine influenza infection in the differential diagnosis of patients with acute febrile respiratory illness who have either been in contact with persons with confirmed swine flu, or who were in one of the five U.S. states that have reported swine flue cases or in Mexico during the 7 days preceding their illness onset. A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample (a simple nose and throat swab)
LABORATORY STUDIES CBC Leukopenia and relative lymphopenia Thrombocytopenia may be present Real time PCR (RTPCR) Viral culture Four-fold rise in swine influenza A(H1N1) virus-specific neutralizing antibodies
There are 19 labs all over our country to test for Swine flu. We have only 5000 kits for testing but attempts are being done to procure more kits.
PREVENTION Prevention in swine- Facility Management Using disinfectants Ambient temperature to control virus in the environment. The virus is unlikely to survive outside living cells for > 2 wks except in cold (above freezing) conditions.
Herd Management Not adding pigs carrying influenza to herds. Virus survives in healthy carrier pigs upto 3 months. Vaccination – Control of swine influenza by vaccination has become more difficult in recent decades, as the evolution of the virus has resulted in inconsistent responses to traditional vaccines.
Prevention in Humans- Pig to Human- Farmers and veterinarians are enconuraged to use a face mask when dealing with infected animals. Use of vaccines on swine. Smoking and not wearing gloves when working with sick animals increases the risk.
Human to Human- Social Distancing- Keeping at least an arm’s length distance from others. Minimizing gatherings Respiratory etiquette Covering coughs and sneezes Hand hygiene Frequent washing of hands with soap and water or with alcohol-based hand sanitizers, especially after being out in public. House hold ventilation
Screening passengers at all international airports, isolating the positive cases and wearing personal protective equipments are the mainstay of prevention.
TREATMENT GUIDANCE NOTE The majority of influenza cases may be cared for at home with the simple supportive care. However, if they develop dangers signs then patients may need to access a health-care facility. These danger signs may include: weakness/not able to stand inability to drink lethargy dehydration and unconsciousness high fever convulsions very difficult/obstructed breathing or shortness of breath
In the case of mild illness, patients should be provided with supportive care at home by a designated caregiver. Supportive care entails- Bed rest Fluids Medication for fever Antibiotics if prescribed Good nutrition
Inpatient treatment should include: Treatment of dehydration with IV or oral rehydration fluids; Supplemental oxygen therapy by face mask rather than nasal prongs; Antibiotics (oral or parenteral) for secondary bacterial infections; Non-aspirin antipyretics for pain and fever Nutritional supplementation as needed. In HIV infected individuals, a distinction between opportunistic pneumonia and secondary pneumonia from pandemic influenza may be difficult.
In health-care settings, a system of triage Patient separation Prioritization of use of antiviral medicines and Personal protective equipment (PPE) which include high efficiency masks ideally (N95 mask or else triple layer surgical mask) gowns, goggle, gloves, caps and shoe covers. According to risk of exposure, and patient management should be in place to focus efforts on the most effective interventions to reduce mortality and any further morbidity.
Antiviral drugs:- There are two classes of such medicines Adamantanes (amantadine and remantadine) Inhibitors of influenza neuraminidase (oseltamivir and zanamivir) Some influenza viruses develop resistance to the antiviral medicines, limiting the effectiveness of chemoprophylaxis and treatment. The viruses obtained from the recent human cases with swine influenza were sensitive to oselatmivir and zanamivir but resistant to amantadine and remantadine.
Oseltamivir is generally available by prescription only. The usual adult dosage for treatment of influenza is 75 mg twice daily for 5 days, beginning within 2 days of the appearance of symptoms and with decreased doses for children and patients with renal impairment. Information is insufficient to make recommendation on the use of the antivirals in prevention and treatment of swine influenza virus infection. Clinicians have to make decisions based on the clinical and epidemiological assessment and harms and benefit of the prophylaxis treatment of the patient.
Side Effects of Oseltamivir (Tamiflu) It may cause bronchitis, insomnia and vertigo, Rarely, anaphylaxis and skin rashes may occur. In children the commonest side-effect is vomiting. In Indian market, the approximate cost in about Rs. 2250/- for ten (75 mg) tablets. DISCHARGE POLICY Adult patients should be discharged 7 days after symptoms have subsided, where as children should be discharged 14 days after symptoms have subsided.
Protection of staff: Standard Precautions – Basic measures to minimize direct unprotected exposure to blood and body fluids. Droplet Precautions – Medical masks when close to patients with respiratory symptoms. Patients and caregivers should be trained to wear and dispose off masks during the infectious period of the patient. The mask need not be worn all day and only when close contact (within approximately 1m) with the caregiver or others is anticipated. Mask should be disposed off safely if wet with secretions.
Self-monitoring – Health staff should monitor their temperatures twice daily. Fevers should be reported. If a staff member becomes unwell, treatment with antiviral as well as supportive care as for other patients should be provided at home by a caregiver.
Vaccine- Influenza viruses change very quickly and the match between the vaccine and the circulating virus is very important to give adequate protective immunity to vaccinated people. WHO is working closely with its partner institutions for an influenza vaccine for preventing the swine influenza infections.
According to Reuters Geneva – The first vaccines to combat H1N1 swine flu should be approved and ready for use from September 2009 (By next month).
The general public must be educated about the signs symptoms and spread of Swine flu. This can be done by television, radio, newspaper etc. PUBLIC AWARENESS
Government of India is taking steps to control this pandemic. There are plans to stockpile 15 billion oseltamivir pills. Steps are also being taken to prevent the spread of the disease.