Within six weeks, swine flu has transited from airplanes to schools, with maximum infections in Delhi and Pune, which on Monday recorded the first death. Data shows that the infection is spreading the fastest among people under 17 years, with one in three of India’s 574 confirmed swine flu cases, till Tuesday night, being school students.
Ironically, what makes young and healthy students more susceptible to infection is their vigorous immune response, which starts an antibodies assault on the new virus. As the body fights inflammation in the lungs, the cells in the lung start leaking fluid, leading to lung collapse.
What adds to their vulnerability is that unlike people over 50 years, they have no immunity against H1N1, one of the many weakened forms of the 1918 Spanish flu virus that continued to cause seasonal flu outbreaks till 1957. That year, another pandemic caused by H2N2 resulted in the new virus becoming the dominant influenza strain, pushing the weakened H1N1 out of circulation.
As a result, those born before 1957 have antibodies against H1N1. But those born after remain unexposed and vulnerable to the virus, putting them at the risk of infection, reports the US Centers for Disease Control (CDC). This also means that those who have been infected with swine flu now, or will get infected, will have immunity against the specific strain of H1N1.
Despite the current pandemic spreading at the fastest ever pace across the world in human history, the World Health Organisation (WHO) India office maintains that the pandemic level is moderate and young; healthy people are not at any higher risk of death.
Of the 134,503 confirmed cases, there were 816 deaths, which can be simplified to 6 deaths in 1,000 people infected. Compare this, every three out of five people who got Bird Flu (H5N1) died since the outbreak started in 2003. And Sars (Severe Acute Respiratory Syndrome) has killed one in 10 people infected since 2002. Annual influenza — the ubiquitous outbreaks three to four times a year — kills up to 500,000 people annually.
According to the WHO, the swine flu death rate will be even lower if the real numbers — and not just the reported cases — are counted. With countries no longer required to register cases with the WHO, only 134,503 have been reported so far — which, said WHO representative to India, S.J. Habayeb, “is the tip of the iceberg.”
The trouble with flu viruses is that they mutate too quickly for epidemiologists to predict which way the pandemic is headed. There are hundreds of flu viruses circulating at any given time. Within four months, the CDC has antigenically characterised 242 influenza A (H1N1) viruses that are causing the present outbreak.
To date, there has been no re-assortment (a virus may get re-assorted when a person or animal gets simultaneously infected by two flu viruses) of the swine flu virus. But if it does happen, we may just have another deadlier wave of infection against which people will have no immunity. Alternatively, they may get milder with time, though past trends indicate that flu pandemics strike harder in the second wave before weakening as more people develop immunity and break the chain of infection.
What’s known is that it will spread and infect thousands more in coming months. With vaccines ready only by the year-end, there is little we can do except take precautions to protect ourselves and perhaps consider vaccination — such as against pneumonia — for high-risk people with heart disease, chronic respiratory diseases, including asthma, as well as diabetes, obesity, cancer and renal diseases.