K. Bharath Kumar, M.S.(USA)

Swine influenza (H1N1)

Swine influenza (also called swine flu, or pig flu) is an infection by any one of several types of swine influenza virus. Swine influenza virus (SIV) is any strain of the influenza family of viruses that is endemic in pigs. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H3N1, H3N2, and H2N3.

Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human influenza, often resulting only in the production of antibodies in the blood. If transmission does cause human influenza, it is called ‘zoonotic swine flu’. People with regular exposure to pigs are at increased risk of swine flu infection.  Pigs experimentally infected with the strain of swine flu that is causing the current human pandemic showed clinical signs of flu within four days, and the virus spread to other uninfected pigs housed with the infected ones. Symptoms of zoonotic swine flu in humans are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness, and general discomfort. The recommended time of isolation is about five days.

The pandemic virus is a type of swine influenza, derived originally from a strain which lived in pigs, and this origin gave rise to the common name of “swine flu”. This term is widely used by mass media. The virus has been found in American hogs and Canadian as well as in hogs in Northern Ireland, Argentina, and Norway. Leading health agencies and the United States Secretary of Agriculture have stressed that eating properly cooked pork or other food products derived from pigs will not cause flu. Nevertheless, on 27 April, Azerbaijan imposed a ban on the importation of animal husbandry products from America. The Indonesian government also halted the importation of pigs and initiated the examination of 9 million pigs in Indonesia. The Egyptian government ordered the slaughter of all pigs in Egypt on 29 April 2009.

History

In June 2009, the World Health Organization (WHO) declared the new strain of swine-origin H1N1 as a pandemic, moving the alert level to ‘Phase 6’, marking the first global pandemic since the 1968 Hong Kong flu.

On October 25, 2009 U.S. President, Barack Obama officially declared H1N1 a national emergency. This novel virus spread worldwide and had caused about 17,000 deaths by the start of 2010. On August 10, 2010, the World Health Organization declared the H1N1 influenza pandemic as officially ‘over’, saying that the worldwide flu activity had returned to typical seasonal patterns.

As of 26 April 2011, an H1N1 pandemic preparedness alert has been issued by the WHO for the Americas.  The affected areas have included the Chihuahua region of Mexico where its severity and work load have been high.  As of May 30, 2010 worldwide update by WHO stated that more than 214 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including over 18,138 deaths.

The virus was first reported in two U.S. children in March 2009, but health officials have reported that it apparently infected people as early as January 2009 in Mexico. The outbreak was first detected in Mexico City on 18 March 2009; immediately after the outbreak was officially announced, Mexico notified the U.S. and World Health Organization, and within days of the outbreak Mexico City was “effectively shut down”.  The new strain was first identified by the Center for Disease Control & Prevention (CDC), USA, in two children, neither of whom had been in contact with pigs.

H1N1 Transmission

Spread of the H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza. Sometimes people may become infected by touching something – such as a surface or object – with flu viruses on it and then touching their face.  The basic reproduction number (the average number of other individuals whom each infected individual will infect, in a population which has no immunity to the disease) for the 2009 novel H1N1 is estimated to be 1.75. A December 2009 study found that the transmissibility of the H1N1 influenza virus in households is lower than that seen in past pandemics. Most transmissions occur soon before or after the onset of symptoms.  The H1N1 virus has been transmitted to animals, including swine, turkeys, ferrets, household cats, at least one dog and a cheetah.  Thermal imaging can detect elevated body temperature, one of the signs of swine flu.

Public Areas (Airports): On 7 May 2009, the WHO stated that containment was not feasible and that countries should focus on mitigating the effect of the virus. They did not recommend closing borders or restricting travel. U.S. airlines had made no major changes as of the beginning of June 2009, but continued standing practices which include looking for passengers with symptoms of flu, measles or other infections, and relying on in-flight air filters to ensure that aircraft were sanitized. Masks were not generally provided by airlines and the CDC did not recommend that airline crews wear them. Some non-U.S. airlines, mostly Asian, including Singapore Airlines, China Eastern Airlines, China Southern Airlines, Cathay Pacific and Mexicana Airlines, took measures such as stepping up cabin cleaning, installing state-of-the-art air filters and allowing in-flight staff to wear face masks.

Schools: U.S. government officials have been especially concerned about schools as the H1N1 flu virus appears to disproportionately affect young and school-age people, between six months and 24 years of age. The H1N1 outbreak led to numerous precautionary school closures in some areas. Rather than closing schools, the CDC recommended that students and school workers with flu symptoms should stay home for either seven days total, or until 24 hours after symptoms subsided, whichever was longer. The CDC also recommended that colleges should consider suspending fall 2009 classes if the virus began to cause severe illness in a significantly larger share of students than the previous spring.  In California, school districts and universities were on alert and working with health officials to launch education campaigns. As of 28 October 2009, about 600 schools in the United States had been temporarily closed, affecting over 126,000 students in 19 states.

Prevention

The H1N1 vaccine was initially in short supply and in the U.S., the CDC recommended that initial doses should go to priority groups such as pregnant women, people who live with or care for babies under six months old, children six months to four years old and health-care workers. In the UK, the NHS recommended vaccine priority go to people over six months old who were clinically at risk for seasonal flu, pregnant women and households of people with compromised immunity. Although it was initially thought that two injections would be required, clinical trials showed that the new vaccine protected adults “with only one dose instead of two”, and so the limited vaccine supplies would go twice as far as had been predicted.

Health officials worldwide were also concerned because the virus was new and could easily mutate and become more virulent, even though most flu symptoms were mild and lasted only a few days without treatment. Officials also urged communities, businesses and individuals to make contingency plans for possible school closures, multiple employee absences for illness, surges of patients in hospitals and other effects of potentially widespread outbreaks. In February 2010, the CDC’s Advisory Committee on Immunization Practices voted for “universal” flu vaccination in the U.S. to include all people over six months of age. The 2010–2011 vaccine will protect against the 2009 H1N1 pandemic virus and two other flu viruses.

Treatment and Drug Resistance: As of December 2010, the World Health Organization (WHO) reported 314 samples of the 2009 pandemic H1N1 flu tested worldwide have shown resistance to oseltamivir (Tamiflu). This is not totally unexpected as 99.6% of the seasonal H1N1 flu strains tested have developed resistance to oseltamivir. No circulating flu has yet shown any resistance to zanamivir (Relenza), the other available anti-viral.

A Wisconsin study published in the Journal of the American Medical Association in September 2010, reported that findings showed that the 2009 H1N1 flu was no more severe than the seasonal flu. “The risk of most serious complications was not elevated in adults or children”, the study’s authors wrote.  Children infected in the 2009 H1N1 flu pandemic were no more likely to be hospitalized with complications or get pneumonia than those who catch seasonal strains.

CDC illness and death estimates from April 2009 to April 2010 are as follows:

• CDC estimates that between 43 million and 89 million cases of 2009 H1N1 occurred between April 2009 and 10 April 2010. The mid-level in this range is about 61 million people infected with 2009 H1N1.
• CDC estimates that between about 195,000 and 403,000 H1N1-related hospitalizations occurred between April 2009 and 10 April 2010. The mid-level in this range is about 274,000 2009 H1N1-related hospitalizations.
• CDC estimates that between about 8,870 and 18,300 2009 H1N1-related deaths occurred between April 2009 and 10 April 2010. The mid-level in this range is about 12,470 2009 H1N1-related deaths.

H1N1 in India

With around 400 people getting infected from the disease (as on April 10, 2012), India is looking at another pandemic like the one that hit way back in 2009. At that time the country was unprepared but now the situation was expected to be under control. After six months of absence, Swine Flu was first reported in Maharashtra in the month of March 2012. Four people had died in just 15 days.  In less than a month, Maharashtra is back again with the highest number of patients suffering from the H1N1 virus with 130 reported cases.  Around three more have died since the March impact.

In 2009, it was Pune which had become like a breeding ground for the killer virus. In 2012, this city alone has recorded 125 infected people with four succumbing to the virus. Andhra Pradesh has reported around 100 people getting affected and 10 deaths. Karnataka reported two deaths while Rajasthan, Gujarat, Himachal Pradesh and Tamil Nadu (at least 29 infected) reporting 1 death each. In just 15 days Madhya Pradesh has reported three deaths.  H1N1 claimed another life in Bangalore on April10, 2012, taking this year’s toll from the disease to six in the city.

In New Delhi, the national capital, at least six cases of Swine Flu has been reported.  In 2012, three cases were registered in January, two in February and one in March.  Swine Flu killed 81 people in Delhi in 2009 and 56 in 2010.  In 2011, only two deaths were reported from Delhi. Swine flu cases have been reported from at least 10 states in 2012. Across the country, the disease claimed more than 2,700 lives from May to December, 2011.

Health ministry figures pegs the numbers of people affected by the virus at above 46,000 from May to December 2011. Doctors contend that there is nothing to worry now because a majority of the population has developed antibodies to fight the virus. They warn that only the high-risk patients, i.e., elderly, people with diabetes, kidney problems, cancer patients and pregnant women are the ones at risk.  Occasional cases in H1N1 infection are likely to occur along with seasonal changes, said Avdesh Kumar, assistant director general, Union ministry of health and family welfare. A team of experts from New Delhi, headed by Kumar, are in Pune to study the pattern of swine flu virus infection currently prevailing in the city and surrounding areas.  Compared to the swine flu pandemic scenario in 2009, the virus is not as active now and there is no significant mutation, he added.  Among the team’s members were the chief medical officer and the consultant epidemiologist of the Integrated Disease Surveillance Program.

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