Intended for healthcare professionals

Analysis

Calibrated response to emerging infections

BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b3471 (Published 03 September 2009) Cite this as: BMJ 2009;339:b3471

Because it is a new virus will no one have immunity to it?

There
cannot be any doubt that the new H1N1 virus is highly contagious but only
produces mild disease, probably is even less virulent than seasonal flu.
Dr.Scheibner has put it very succinctly 'Much ado about nothing'.

I have recently returned from India and what struck me was the
valuable resources diverted by the officials into the anti-flu campaign,
which at that time had reported only a single case of H1N1 flu in an
Airline passenger who had mild fever lasting for a day. Thousands of
casualties to preventable diseases like diarrhoea, malaria an
tuberculosis are a daily occurrence there.

Peter Collignon referred to the inappropriate fear which has pushed
us to inappropriate responses. May I refer to inappropriate information
which has been used to create unnecessary fear both by the WHO and the UK swine flu information leaflet: because it is a new virus no one will have
immunity to it (1,2).
H1N1 has been around since 1918. This is a new
variant, a fact that I don't argue.

But is it true that no one will have immunity to it? Millions have
been infected. Most patients had only mild symptoms. The death rate and
overall admission rate were the same or even lower than for seasonal flu. How
could this have happened if the infected population did not have any
immunity? In fact they had good immunity.

Two distinct immune systems operate in our body:innate immunity and
acquired immunity.

Innate immunity is a primitive but powerful immune system that comes
into operation immediately after infection and does not require
previous exposure to the invading microbe. Pattern recognition receptors
in the host cell recognise pathogen associated molecular patterns in a
general manner and signal the immune system to destroy the parasite. There
are also thousands of antimicrobial peptides which keep the pathogen in
check.

Acquired immunity operates by lymphocytes which specifically
recognise antigenic epitopes in the pathogen. Quite a large percentage of
these epitopes will be shared by the different flu viruses and the
vaccines already in use. In fact most of us have good immunity to the new
H1N1 virus as demonstrated by the epidemiology of the present Pandemic.

1.World Health Organization. Ten things you need to know about
pandemic influenza. 2005.

2.Important Information about Swine Flu. www.direct.gov.uk/swineflu

Competing interests:
None declared.

Competing interests: No competing interests

13 September 2009
Dr.Nadaraja Bathirunathan
Retired Lecturer
Clinical Sciences, MRI,M14 9PL