Mutant menace and its health hazards

H1N1 is not the only virus that has taken the world hostage. Every year, as the temperatures dip and the air becomes dry, new strains of flu viruses emerge.

The viruses that emerge with slight changes only cause seasonal flu. Since they have been circulating in the air for quite some time, most people are immune to them and medicines are readily available to tackle any outbreaks they cause. There are others that emerge as “novel strains” and can have the ability to spread more quickly. They do not encounter the “firewall” of protection from pre-existing immunity in a person. Since no medicine is available to tackle them, a large section of the population is susceptible to it, resulting in pandemics.

Rise of novel viruses
According to WHO, 5-10 per cent of adults and 20-30 per cent of children are infected by one form of flu or the other every year. Of late, more number of “novel strains” is causing epidemics. Every year, these epidemics result in three to five million cases of severe illness, and 250,000-500,000 deaths worldwide. In a report in February, WHO states that an influenza pandemic is the most global of infectious disease events currently known.

Although we know the general mechanism by which new influenza viruses emerge, our basic knowledge of how these viruses acquire pandemic potential is rudimentary. So far, all we know is that at least 18 HA (haemagluttinin) and 11 NA (neuramin- idase) subtypes of viruses are circulating in the air, which can constantly reinvent them by exchanging genetic material. This process appears to be happening at an accelerated pace. Most of these novel strains are being churned out by animals and birds. Since the start of 2014, the World Organization for Animal Health, an inter-governmental body, has been notified of 41 outbreaks in birds involving seven different viruses in 20 countries in Africa, the Americas, Asia, Australia, Europe and West Asia.

Climatic conditions are exacerbating the problem. A study published in Proceedings of the National Academy of Sciences in 2013 shows that the four recent human influenza pandemics—reported in 1918, 1957, 1968 and 2009—were first identified in boreal spring or summer and were preceded by La Niña conditions in the equatorial Pacific. Changes in the phase of the El Niño-Southern Oscillation have been shown to alter the migration, fitness and mixing of migratory birds with domestic animals. Thus, La Niña conditions bring divergent subtypes of flu virus together, leading to generation of novel strains.

Another study published in January 2013 issue of PLoS Currents suggests that warmer-than-average winters tend to lead to early and severe influenza seasons. In 2012-13, the influenza season had an unusually early and severe start in the US. An analysis of climate and past US influenza epidemic seasons indicated that warm winters tend to be followed by severe epidemics. “Fewer people are infected with influenza during warm winters, thereby leaving an unnaturally large fraction of individuals susceptible to influenza in the next season. This can lead to early and severe epidemics,” say the researchers. In the event of continued global warming, warm winters such as that of 2011-12 are expected to occur more frequently, they warn.

Global authorities are well aware of the situation but are far from tackling it. Vaccination is said to be one of the first steps towards preparing for an epidemic. To figure out which specific strains to target, over 100 countries study influenza trends and collaborate with WHO. Usually, they select three or four out of hundreds. Then, based on forecasts and a bit of luck, each country decides which strains to include in the next vaccination.

Prevention is the real cure
But vaccines have a problem. Since the 2004-05 flu season, US researchers estimate that the effectiveness of vaccines has reduced to 10-60 per cent. This could be because the genetic make-up and antigenic properties (proteins that activate the immune system) of viruses are changing. For example, since February 2014, the genetic make-up and antigenic properties of the H3N2 Virus circulating in North America and Europe has changed. As a result, the effectiveness of the current seasonal vaccine in reducing influenza-related illnesses was only 23 per cent in the US.

In January this year, the Indian Medical Association mentioned in a press release that current seasonal influenza vaccines are not expected to provide protection against human infection with avian or swine influenza viruses. This calls for a need to develop more potent vaccines and shorten the production time. During a severe pandemic, many lives are lost in the three to four months that are needed to produce vaccines. Since current seasonal vaccines are ineffective against novel pandemic strains, recent efforts have focused on development of broadly protective or universal influenza virus vaccines that can provide immunity against seasonal flu as well as potential pandemic virus.

So, the best way is to prevent major outbreaks of influenza. And this requires understanding flu viruses better. For instance, in August 2014 WHO introduced guidelines for prevention and control of influenza-like illnesses, suggesting that patients should be kept in isolation. However, the specific duration of infectious period for many types of flu, such as swine flu, is unknown. So there is no consensus on how long a patient should be kept in isolation.

Researchers of Columbia University’s Mailman School of Public health are working on the prediction of influenza epidemics. “We do real-time forecasts for over 100 cities in the US. In the future, we would like to expand this effort to other regions around the world, including India,” says Yang. Forecasts, if reliable, would help public health sectors devise effective intervention measures to prevent the spread of the flu through efficient allocation of resources such as vaccines and antivirals, and better education of the public, he adds.

Rajib Dasgupta of JNU says effective communication is an important tool for reducing the impact of spread of infectious diseases, like the current spread of swine flu. “Only messages about the spread of an infectious disease result in panic. So the government needs to actively engage with the affected population. This can be done by communication specialists who can design campaigns to tackle the panic, and ensure that no critical case is ignored. Unfortunately, India’s public health system does not involve communication specialists,” says Dasgupta.

Conditioned by a nervous watch over the lethal H5N1 bird-flu virus in humans in 2003 and then the appearance of H1N1 virus in 2009, scientists are now alert and prepared. But they are more scared than ever. As the virus keeps mutating and evolving, the worst may still be out there.  DOWN TO EARTH
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