WE have been hit by yet another infectious disease that is causing panic among our hapless citizens. This winter, as in many past winters, the influenza virus has struck. There is a rush for doctors’ clinics and emergency rooms, and frenzy to receive the influenza vaccine as news headlines scream reports of ‘influenza deaths’.

Influenza (abbreviated ‘flu’) begins with body pain, scratchy throat and runny nose, followed by high fever with chills, headache, and a dry cough. This lasts three to four days; there is a period of recovery with fatigue and loss of energy for few more days. There is work or school absenteeism, and slow return to normal activity, while dry cough persists another few days.

A common cold, on the other hand, is milder, and is caused by an unrelated virus. A powerful sneeze or cough sends an aerosol spray containing millions of virus particles, which remain suspended in the air for a while. People within range of the spray inhale the virus and the infection grows into an outbreak, expands to an epidemic, and, with ease of travel, involves people in other cities, countries and continents, causing a global pandemic. In the majority of instances, the treatment is only rest, fluids and fever control. Antibiotics are unnecessary.

Samples must be examined to determine the current virus strain.

The influenza virus has some interesting features: it has projections consisting of protein on its surface, called Haemagglutinin (H), and Neuraminidase (N) which have the propensity to ‘drift’ and ‘shift’, and ultimately mutate into a subtype of the original virus. Moreover, the genetic material of human influenza virus is known to have mixed with the bird and swine influenza viruses to form a novel hybrid virus. These changes are depicted in the H and N proteins, and are given nomenclatures such as H1N1, H5N2, etc.

Once a virus circulates in a community for several years, people develop immunity and react less severely. This is called ‘seasonal flu’. When a novel virus enters the community, the population does not have immunity against the new virus, and affected persons react severely; the infection spreads rapidly and causes more fatalities. This is called ‘pandemic flu’.

The symptoms of the illness, however, are same in both. Patients who develop more severe symptoms or are likely to die from pandemic flu are already in poor health from previous lung disease from smoking, uncontrolled diabetes, heart failure, or from medicines that reduce body defence mechanisms. The very young, very old and pregnant women, too, are at high risk for complications or mortality.

The Spanish pandemic influenza of 1918 is known to have killed millions of people around the world. One could postulate that during the First World War, living conditions were not as affluent as they are today. Medical care was nascent, chronic diseases were untreatable; smoking was a well-healed habit, and food and medicines were scarce. These factors lead to excess deaths. Modern living styles, improved healthcare and healthier habits have led to better survival. Moreover, vaccines have helped save lives.

The only certain way of distinguishing seasonal from pandemic flu is in the laboratory through a sample taken from the nose or throat on a special medium. The specimen is processed in special labs that can perform the test by PCR. Although the result may not always determine further treatment, it is important from the public health point of view since the final tally of cases will verify the presence of possibly a newly introduced virus. Ultimately, WHO collates reports from all over the world to determine how and where the infection spreads, and makes appropriate recommendations for prevention, manufacture of vaccines, and treatment.

The most recent influenza pandemic occurred in 2009 wherein a new strain of influenza virus A (H1N1) 2009 “emer­ged, spread rapidly around the world, and caused sustained community-level outbreaks. Currently available data suggest that the overall severity of the influenza pandemic was moderate”. In 2008-2011, Pakistan experienced a mix of both seasonal and pandemic flu, as evidenced by tests in a central laboratory at the National Institute of Health in Islamabad. The present outbreak of the type of virus cannot be substantiated until samples are examined and reported.

The flu vaccine was first manufactured in 1930s. The quality of its production has considerably improved over years. The new strains of H and N are incorporated into the vaccine each year to protect against the current strain/s. Although many resist its use, overall it has decreased the incidence and severity of symptoms. It must be understood, though, that the flu vaccine does not prevent against the common cold or against other circulating strains of the virus.

The only way to prevent the flu or its ill effects is to maintain a healthy lifestyle, balanced nutrition, hand hygiene and self-protection.

The writer is an infectious disease specialist.

Published in Dawn, January 24th, 2016