Some facts about swine flu

1. Among human influenza A viruses, three major subtypes of hemagglutinins - H1, H2, and H3 - and two subtypes of neuraminidases - N1 and N2 – are known. Influenza B viruses have been shown to have a lesser inclination for antigenic changes, and merely antigenic drifts in the hemagglutinin have been noted.
2. Swine flu is H1N1.
3. Reproductive number of swine flu is 1.2. One infected person will infect 1.2 others. The same for coronavirus COVID-19 is 3.
4. The incubation period for the common flu (seasonal influenza) is around 2 days. Incubation period for SARS is 2-7 days, MERS is 5 days and COVID-19 is 2-14 days.
5. Swine flu was declared as a Public Health Emergency of International Concern from 26^th April, 2009 to 10^th August, 2010. Since then it is considered as an endemic virus with focal outbreaks in winter.
6. Currently there is an outbreak in Delhi. There was a similar outbreak in Malaysia in December.
7. H1N1 virus binds to receptors in the upper respiratory tract and causes relatively mild disease. It has become endemic in the population.
8. On the other hand, H7N9 virus binds to receptors in the lower respiratory tract and has a case-fatality rate of about 40%. COVID-19 binds to both upper and lower respiratory tract receptors and has a case fatality of 2%.
9. The case fatality of swine flu is lowest - COVID-19 2%; MERS 34%; SARS 10%; Ebola 50%; Smallpox 30-40%; Measles 10-15% developing countries; Polio 2-5% children and 15-30% adults; Diphtheria 5-10%; Whooping cough 4% infants < 1yr, 1% children < 4 years; Swine flu < 0.02%; Seasonal flu 0.1%.
10. The mitigation precautions include respiratory hygiene and cough etiquette combined with hand wash contact precautions. The precautions are same as for any coronavirus.
11. There is no data that COVID-19 and H1N1 will not coexist. Coexistence of two respiratory viruses have been seen in bats.
12. Remember - no fever, no flu.
13. Fever with cough and cold is flu unless proved otherwise.
14. No breathlessness, no admission.
15. No breathlessness, no testing.
16. All mild cases should be treated with online consultations.
17. All individuals with severe disease (requiring hospitalization or with evidence of lower respiratory tract infection) or at high risk for complications should receive antiviral drugs.
18. When there is an indication, antiviral therapy should be started as early as possible since benefit is most likely when treatment is started within the first 48 hours of illness.
19. There should not be delay in treatment while the results of diagnostic test are awaited. It should also not be withheld in patients with indications for therapy who present >48 hours after the onset of symptoms, especially among patients requiring hospitalization.
20. Patients who have a negative rapid antigen test for influenza but with high clinical suspicion for influenza infection should be treated with antivirals since the sensitivity of these tests may be low.
21. Start oseltamivir: Confirmed or suspected cases, severely ill, requiring hospitalization, lower respiratory tract infection, showing signs of rapid clinical deterioration, at increased risk for complications.
22. Patients with uncomplicated influenza who have had >48 hours of influenza signs and symptoms notto be treated with antivirals.
23. Give anti-viral therapy for symptomatic outpatients with uncomplicated influenza who are not at high risk for influenza complications but who are household contacts of persons at high risk for influenza complications, particularly those who are severely immunocompromised.
24. Antivirals should be given to symptomatic healthcare providers with uncomplicated influenza not at high risk for influenza complications but routinely care for patients who have a high risk for influenza complications, especially those who are severely immunocompromised

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA