Swine flu cases may hit 1 crore in December

For those who think the current panic over swine flu — influenza A (H1N1) — is overblown, here’s a sobering thought: the flu is on the upswing, and by December the numbers of those testing positive could cross one crore.

Based on trends reported till August 9, when the country had 864 officially confirmed H1N1 cases, DNA commissioned Fractal Analytics, a leading analytics services company, to project trends into the near future. The analysis, which factors in weather and other conditions, suggests that reported cases will touch 3,000 by the second week of September, but will rise dramatically as winter nurtures the virus. The numbers could hit 1.5 million by mid-November before climbing to over a crore by the end of 2009.

While these are rough projections, the numbers can be refined as more data becomes available over the next few weeks. DNA spoke to epidemiologists in Delhi and they confirmed that the real spike in H1N1 cases will happen by November-December.

“The H1N1 virus is not going to slow down soon. It will peak by November-December, when other influenza viruses too are most active. H1N1 is a new virus and people do not have immunity against it at present,” said Dr RP Vashist, head of public health, Delhi government.

While carrying out the statistical analysis, Fractal compared the growth of H1N1 in the UK and US. The analysis was overlaid with the historical pattern of the spread of flu in India. The data on which the projection was made suggested an exponential rate of growth.

The steep climb is in line with the World Health Organisation’s projection that 30% of the world’s population will be infected by the H1N1 virus during the current pandemic. Health experts in Delhi were unwilling to make predictions about how many people will be infected in India and what the mortality rate will be, but they are using the pattern of common seasonal influenza as the baseline to arrive at conclusions. “Common seasonal flu affects about 20% of the world’s population, despite vaccines being available. Roughly 2.5-5 lakh people die annually due to common flu while about 50 lakh are hospitalised, despite the larger part of the world’s population being immune to these viruses.

The reason is that these viruses keep mutating from time to time,” Vashist said. Epidemiologists do not hold out immediate hope of relief. Paradoxically, they are predicting that higher the initial outbreak, better the chances of people developing a natural resistance to the virus.

Swine flu will start retreating only after a level of ``herd immunity’’ has been reached.
“Most of the time, when infection travels in a community, it remains mild and sub-clinical, leading to herd immunity. This means that when the virus reaches a critical level, its transmission among people stops. But it is still very early days for H1N1 in India and it will take some time for it to reach its critical level,” says Dr Kameshwar Prasad, director of clinical epidemiology at the All India Institute of Medical Sciences (AIIMS).

 “H1N1 is almost like the common flu, with the main difference being that the latter stays for 2-4 days while swine flu stays for 5-6 days. The mortality linked to this strain of virus is similar to that of seasonal influenza, only its profile has changed. As its stays in the atmosphere for long, the community develops antibodies to resist it,” adds Dr NK Ganguly, former director general of the Indian Council of Medical Research (ICMR).

According to Vashist, senior citizens are less likely to be infected by swine flu, probably because they have already developed some kind of resistance from another virus which had circulated in the 1968s as Hong Kong flu. Over one million people had died worldwide at that time, most of them being elderly.

“Even though the virus in 1968 was not H1N1, there is a theoretical possibility that a certain population may have developed cross-resistance. But the other reason for senior citizens not catching the infection is the fact that they are less mobile, and are mainly confined to homes. They are thus less exposed to the virus,” said Prasad.

Ganguly said H1N1 is showing three patterns. It is mildest in persons who are infected, but are asymptomatic; it is mild in persons showing classical flu symptoms like high fever, muscle pain, cold and cough; it is severe in persons who are diabetic, suffering from hypertension, asthma and other ailments. In these persons, H1N1 may lead to respiratory distress, sudden dip in blood pressure and organ failure leading to death. 
No measure can be sufficient against such viral attacks.

While most of the developed countries have now shifted focus from containment to cure, the situation in India is still at a stage where containment is working.

Interviews of epidemiologists by Vineeta Pandey in Delhi