As the symptoms of swine flu are similar to those of the common cold, many individuals do not take it seriously until it reaches a critical stage, hence this article provides a proper understanding of swine flu and also furnished treatment management for physicians to manage this viral infection. 

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Since the 2009 pandemic, swine flu has become endemic, and mortality is disproportionately concentrated among older individuals with co-morbidities. Approximately once every decade or two, major mutations in the virus may cause a significant rising trend. The new strain may have the same impact on a native population as the original strain.

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What is H1N1 or swine flu?

The influenza viruses are members of the family Orthomyxoviridae. Of the four recognised genera, the influenza A virus is the most prevalent human pathogen. Both hemagglutinin (H) and neuraminidase (N) proteins enable the virus to infect cells in the respiratory and gastrointestinal tracts of humans. At least 18 H subtypes and 11 N subtypes exist, and combinations of these are used to designate the strain type.

Swine flu is a form of influenza A virus, so-called because it is a reassortment of human, pig, and avian influenza viruses. It has the H1 and N1 subtypes of these proteins, thus its designation as H1N1. It caused a pandemic in 2009, and since then, H1N1, H3N2, and certain Influenza B strains have been the prevalent viruses circulating globally.

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Why has there been a dramatic increase in cases?

Monsoon is thought to be the peak season for the illness. This year's increase may be due to a combination of three factors:

1. First, this is the first monsoon without lockdowns since 2020.
2. Second, COVID-19 may have increased people's awareness, resulting in early healthcare access.
3. Third, the broad acceptance of nasopharyngeal swabs and improved accessibility to diagnostic test kits have led to an increase in testing. Nonetheless, it is plausible that this is a real rise, and that we are seeing an unprecedented year.

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What epidemiological factors contributed to its rise?

Every few years, the surface proteins of the influenza virus might undergo reassortment. This may make previous protection useless since the virus is able to dodge the antibodies produced in response to exposure to earlier strains.

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What distinguishes COVID-19 symptoms from those of the swine flu and how can one distinguish the symptoms?

Similar symptoms might be difficult to differentiate. Both illnesses present with the following symptoms:

• Fever
• Nasal congestion 
• Headache
• Sore throat
• Muscular aches
• Pains
• Cough
• Diarrhoea is also present in both cases

Perhaps secondary bacterial infections are more prevalent in influenza than in COVID-19 during the previous several years. It is hard to differentiate between influenza and COVID-19 based on symptoms in the absence of a documented close interaction with a person with influenza. Only testing can prove the presence of an infection.

Communicability

Incubation period - 1-7 days.

From 1 day before to 7 days after the onset of symptoms. If the illness persists for more than 7 days, the chances of communicability may persist till the resolution of the illness. Children may spread the virus for a longer period.

Investigations

1. For the examination and treatment of a patient exhibiting the aforementioned symptoms, routine diagnostic procedures will be necessary. As required, they might include haematological, biochemical, radiological, and microbiological testing.
2. Confirmation of Pandemic influenza A(H1N1) infection is through Real-time RT PCR or Isolation of the virus in culture or a Four-fold rise in virus-specific neutralising antibodies.
3. Clinical specimens such as nasopharyngeal swabs, throat swabs, nasal swabs, wash or aspirate, and tracheal aspirate (for intubated patients) are required for diagnostic confirmation.

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What are the precautions that should be taken?

Like COVID-19, influenza tends to produce the most severe illness in immunocompromised individuals. These patients would include the elderly, those with immunosuppressive conditions or using immunosuppressive medications, pregnant women, and those with comorbidities.

These persons should avoid crowded, confined, and poorly ventilated locations and should wear a mask while inside. Those who have not gotten the yearly influenza vaccination this year should do so after checking with a physician.

Frequent hand sanitisation and isolation while unwell are beneficial practices for protecting oneself and one's close contacts. When administered early, Oseltamivir has the ability to shorten the length of sickness and decrease its transmissibility; hence, it is suggested for high-risk persons.

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Who needs to be hospitalised?

Immunocompromised persons make up the majority of those with severe illness. After the first viraemic phase, influenza often makes persons susceptible to subsequent bacterial infections, and antibiotics are required if there are signs of a secondary infection.

Viral respiratory infections are known to exacerbate underlying chronic conditions, and people with COPD, asthma or underlying heart disease are particularly susceptible.

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Treatment

Antiviral drugs including Oseltamivir (Tamiflu) and Zamanavir are used to treat swine flu (Relenza). In contrast to Tamiflu, Relenza is a nasal spray. If pneumonia or chest infections develop, it may be required to provide further antibiotics. You must follow the ensuing safety precautions and practice appropriate hand- and respiratory hygiene if hospitalisation is not required.

Treatment Recommendations by MoHFW-

The guiding principles are:

1. Early implementation of infection control precautions to minimise nosocomial / household spread of disease
2. Prompt treatment to prevent severe illness & death.
3. Early identification and follow-up of persons at risk.

Isolation facilities: if a dedicated isolation room is not available then patients can be cohorted in a well-ventilated isolation ward with beds kept one metre apart.

Oseltamivir Medication
Oseltamivir is the recommended drug both for prophylaxis and treatment. In the current phase, if a person conforms to the case definition of the suspect case, then he would be provided Oseltamivir.

The dose for treatment is as follows:

By Weight:

• For weight <15kg 30 mg BD for 5 days
• 15-23kg 45 mg BD for 5 days
• 24-<40kg 60 mg BD for 5 days
• >40kg 75 mg BD for 5 days

For infants:

• <3 months 12 mg BD for 5 days
• 3-5 months 20 mg BD for 5 days
• 6-11 months 25 mg BD for 5 days

It is also available as a syrup (12mg per ml ).
If needed dose & duration can be modified as per the clinical condition.

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Adverse reactions

1. Oseltamivir is generally well tolerated, and gastrointestinal side effects (transient nausea, and vomiting) may increase with increasing doses, particularly above 300 mg/day.
2. Occasionally it may cause bronchitis, insomnia and vertigo. Less commonly angina, pseudomembranous colitis and peritonsillar lar abscess have also been reported.
3. There have been rare reports of anaphylaxis and skin rashes.
4. In children, the most frequently reported side effect is vomiting. Infrequently, abdominal pain, epistaxis, bronchitis, otitis media, dermatitis and conjunctivitis have also been observed.
5. There is no recommendation for dose reduction in patients with hepatic disease.
6. Though rare reporting of fatal neuropsychiatric illness in children and adolescents has been linked to oseltamivir, there is no scientific evidence for a causal relationship.

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Supportive therapy

• IV Fluids
• Parenteral nutrition
• Oxygen therapy/ ventilatory support
• Antibiotics for secondary infection
• Vasopressors for shock
• Paracetamol or ibuprofen is prescribed for fever, myalgia and headache

1. Salicylate/aspirin is strictly contra-indicated in any influenza patient due to its potential to cause Reye’s syndrome.
2. The suspected cases would be constantly monitored for clinical /radiological evidence of lower respiratory tract infection and for hypoxia (respiratory rate, oxygen saturation, level of consciousness).
3. Patients with signs of tachypnea, dyspnea, respiratory distress and oxygen saturation of less than 90 per cent should be supplemented with oxygen therapy. Types of oxygen devices depend on the severity of hypoxic conditions which can be started from an oxygen cannula, simple mask, partial re-breathing mask (mask with reservoir bag) and non-re-breathing mask. In children, oxygen hoods or head boxes can be used.
4. Patients with severe pneumonia and acute respiratory failure (SpO2 <90% and PaO2 <60 mmHg with oxygen therapy) must be supported with mechanical ventilation. Invasive mechanical ventilation is the preferred choice. Non-invasive ventilation is an option when mechanical ventilation is not available. To reduce the spread of infectious aerosols, the use of HEPA filters on expiratory ports of the ventilator circuit / high flow oxygen masks is recommended.
5. Maintain airway, breathing and circulation (ABC); Maintain hydration, electrolyte balance and nutrition.
6. If the laboratory reports are negative, the patient would be discharged after giving a full course of oseltamivir. Even if the test results are negative, all cases with strong epidemiological criteria need to be followed up.
7. Immunomodulating drugs have not been found to be beneficial in the treatment of ARDS or sepsis-associated multi-organ failure. High-dose corticosteroids in particular have no evidence of benefit and there is potential for harm. Low-dose corticosteroids (Hydrocortisone 200-400 mg/ day) may be useful in persisting septic shock (SBP < 90).
8. Suspected cases not having pneumonia do not require antibiotic therapy. Antibacterial agents should be administered, if required, as per locally accepted clinical practice guidelines. Patients on mechanical ventilation should be administered antibiotics prophylactically to prevent hospital-associated infections. It has been observed that some of the patients even though asymptomatic, continue to test positive for influenza A H1N1. A treated and recovered patient, even though testing positive, has very little possibility of infecting others.

In view of the above, the following recommendations are made:

1. Patients who responded to treatment after two to three days and become totally asymptomatic should be discharged after 5 days of treatment. There is no need for a repeat test.
2. Patients who continue to have symptoms of fever, sore throat etc. even on the 5th day should continue treatment for 5 more days. If the patient becomes asymptomatic during the course of treatment there is no need to test further.
3. For patients who continue to be symptomatic even after 10 days of treatment or those cases with respiratory distress and in whom secondary infection is taken care of, and if the patient continues to shed virus, then the resistance of the patients to antiviral would be tested. The dose of anti-viral may be adjusted on case to case basis. The family of patients discharged earlier should be educated on personal hygiene and infection control measures at home; children should not attend school during this period.

Chemoprophylaxis

1.  Chemoprophylaxis for health care workers at high risk.

• The treating physicians and other para-medical personnel at the isolation facility would be put on chemoprophylaxis.

2. Chemoprophylaxis for contacts

• Chemoprophylaxis is advised for those contacts with high risk (with underlying systemic diseases; extremes of age[< 5 years and 65> years]

All close contacts of suspected, probable and confirmed cases. Close contacts include household /social contacts, family members, workplace or school contacts, fellow travellers etc.
All health care personnel coming in contact with suspected, probable or confirmed cases

Oseltamivir is the drug of choice- Prophylaxis should be provided till 10 days after the last exposure (maximum period of 6 weeks)

By weight

• For weight <15kg 30 mg OD
• 15-23kg 45 mg OD
• 24-<40kg 60 mg OD
• >40kg 75 mg OD

For infants

• <3 months not recommended unless the situation is judged critical due to limited data on use in this age group
• 3-5 months 20 mg OD
• 6-11 months 25 mg OD

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Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Monish Raut is a practising super specialist from New Delhi.