




































In ternationa l
Scholars
Journa ls

 

African Journal of Pig Farming ISSN 2375-0731 Vol. 2 (8), pp. 001-005, August, 2014. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

 

Review 

 

Swine flu: A threat to human health 

 
Syeda Samra Iqbal Jafri*, Muhammad Ilyas and Muhammad Idrees 

 
National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan. 

 
Accepted 12 September, 2013 

 
Influenza virus has caused major global epidemics since 1918. Although this commonly circulating viral 
strain is not virulent enough to cause mortality, but the re-assortment of viral genome to mutate at a 
very high rate can lead to the emergence of a highly virulent strain that may lead to next pandemics. 
Swine flu is an example of re-assortment of two viruses in pig causing thousands of deaths in the 
whole world especially in the United States of America by zoonotic jumps. This review addresses the 
biological and epidemiological aspects of swine flu virus and efforts to have a control on the virus 
globally. 

 
Key words: Swine influenza, serotypes, pandemic, vaccine. 

 
 
INTRODUCTION 

 
Flu is an ancestrally old illness which started in birds 
initially and then slowly diversified to all warm blooded 
animals on earth in an era of thousands of years. Global 
population affected by annual flu is estimated to be 5 - 
15%. Although most flu cases are mild but may cause 
severe illness in 3 - 5 million people and about 250,000 - 
500,000 deaths worldwide. Mostly chronically unhealthy 
people, the old and high risk populations of infants face 
severe illness and deaths in industrial countries (EPI Fact 
Sheet, 2007). Though the forms of animals are different 
organisms but flu viruses can travel from one organism to 
another organism of different species. Humans are also 
included in this exchange of viruses. Re-assortment is the 
process through which a virus organizes its genetic 
material and thus a hybrid variety of super-virus comes 
into existence. Because this is a newly originated form so 
there is no innate or adaptive immunity present and flu 
spreads effectively and easily. Swine flu is a respiratory 
disease caused by a reassortant virus and has elements  
 
 
 
*Corresponding  author.  E-mail:  milyaskh@hotmail.com.  Tel: 
+92-300-5740568. 
 
Abbreviations: SARS, Severe acute respiratory syndrome; 

CDC, Centre of Disease Control; WHO, World Health 

Organization; DHS, Department of Homeland Security; FDA, 

Federal Drug Administration. 

 
 
 
 

 
of virus found in pigs. Swine flu virus acts similar to the 
Spanish flu, 1918, which caused the death of 20 million 
people; swine flu is showing the same age related 
mortality. Swine flu caused a pandemic flu outbreak by 
spreading from human to human worldwide. Because it is 
caused by a re-assortant virus so no one has immunity 
against this virus and is at risk of being caught by flu. So 
not only children, older people and diseased persons but 
also healthy people are at risk. Swine flu virus is made up 
of tiny droplets and can spread through so many ways. 
 
 
 
Epidemiology 

 
The key thing is going to be the epidemiology. Swine flu 
virus is a “reassortant virus” containing genes from a 
number of sources. Though the swine flu virus is specie 
specific but it can easily cross the specie barrier and 
zoonotic jumps were seen in swine flu virus from pigs to 
humans. Once in humans, it can spread in whole 
population with ease. Normally when virus jumps from 
one species to another, it gets ill- adapted due to its 
inability to multiply and spread in the foreign territory. But 
swine flu virus got well adapted to humans, enabling it to 
transmit efficiently from one person to the next. Swine flu 
infection transmits to humans through pigs and then 
human-to-human transmission is possible but spread is 



        
 

 Table 1. Pandemics of 20
th

 century due to influenza virus.     
 

        
 

 Pandemic due to flu 
Prototype strain Subtype Infected people Death rate Case fatality rate 

 

 virus and causative 
 

 strain       
 

 Spanish flu A/FM1/47 H1N1 (Yu-Chia et 0.5-1 billion infected 20-100 million >2.5%  
 

   al., 2006; Li 2008)  (WHO, 2005; (Taubenberger et 
 

     Knobler et al., al., 2006)  
 

     2005; Patterson   
 

     et al., 1991)   
 

 Asian flu A/Singapore/57 H2N2 (Yu-Chia et  2 million (WHO, <0.1%  
 

   al., 2006)  2005) (Taubenberger et 
 

      al., 2006)  
 

 Hong Kong flu A/Hong Kong/68 H3N2 (Yu-Chia et  1 million (WHO, <0.1%  
 

   al., 2006)  2005) (Taubenberger et 
 

      al., 2006)  
 

 Seasonal flu  Mainly A/ H3N2, (5-15%) 340 million 250,000- <0.05%  
 

   A/H1N1 and B - 1 billion (WHO, 500,000/year (Taubenberger et 
 

    2009) (WHO, 2003) al., 2006)  
 

 Russian flu A/USSR/77 H1N1     
 

 
 

 

limited to close contacts or closed groups of people. 
According to the working party report of UK Government 
in 2000, “There’s something like 500,000 people airborne 
around planet Earth at any instant in time”. This shows 
the potential of swine flu virus to spread far and wide very 
quickly and can lead to a pandemic. Swine flu outbreak 
occurs in pigs in autumn and in winter in temperate 
zones. Disease is considered as endemic. Sporadic 
human infections and outbreaks are occasionally 
reported. 

 
 

GLOBAL PANDEMICS OF 20
TH

 CENTURY DUE TO 

INFLUENZA VIRUS 
 

Three major global epidemics of the 20th century have 
been caused by Influenza A virus, the Spanish flu in 1918 

- 1919, the Asian Flu in 1956 - 1958 and the Hong Kong 
flu in 1968 - 1969 by undergoing major genetic changes 
for which population did not poses significant immunity 
[WHO Fact Sheet; Kilbourne, 2006]. Over the past 
century several pandemic threats have been caused by 
H1N1 subtype, which include the 1947 pseudo-pandemic, 
swine flu outbreak 1976 and Russian flu 1977 [Kilbourne 
ED, 2006]. The SARS epidemic by SARS coronavirus in 
South East Asia further increased the level of alerts. Then 
the advent of H5N1 bird flu outbreaks further increased 
the level of preparedness though the strains have limited 
human-to-human transmission ability [Yu-Chia et al., 
2006; Beigel et al., 2005]. Table 1 shows the effect of 
Influenza virus on people in 20th century. 

 
 

 

SWINE FLU 

 

Swine flu, a global outbreak took its origin from a large 
pig farm in Mexican town of La Gloria in Veracruz State 
with evidence that Mexico was already in midst of an 
epidemic for months before the outbreak was recognized. 
It was first detected in Mexico City on March 18, 2009 
(Kilbourne, 2006). This new strain was first diagnosed in 
two children, having no contact with pigs, by the CDC, 
first on April 14, 2009 in San Diego Country, California 
and a few days later in near by Imperial County, 
California (New York Times, 2009), which was not 
identified as a new strain in Mexico until April 24, 2009 
(Morb Mortal Wkly Rep, 2009). WHO has been notified of 
swine flu cases from the United States and Spain. The 
government closed down most of the private and public 
offices and facilities of Mexico City to stop the spread of 
disease. WHO declared it as pandemic in early June and 
noticed the moderate severity of disease. From Mexico 
the virus spread with un-plecedented speed to Southern 
hemisphere and less developed countries. Outbreaks in 
North America, South America, Europe (including the 
United Kingdom, Italy and Sweden), Africa (Kenya), and 
in parts of the Eastern Asia including China and Japan 
has also been reported. 

Swine flu is a highly contagious acute respiratory 
disease of pigs, caused by Swine Influenza A Virus, 
referred to as the novel H1N1. The most common sub-
type is H1N1 in case of swine flu but other serotypes e.g. 
H1N2, H3N1, H3N2 are also found circulating in pigs. It is  
thought that H3N2 strain was originally introduced into the 



 
 
 

 
Table 2. Various techniques used for the laboratory diagnosis of swine influenza.  

 
Procedure Influenza type detected Acceptable specimen Time for results (h)   

Real time PCR A 
Naso pharyngeal (NP) swab, throat swab, nasal 

 

wash, bronchial wash, nasal aspirate, sputum  

  
 

Antigen detection 
A 

Naso pharyngeal (NP) swab, throat swab, nasal 
 

ELISA wash, bronchial wash, nasal aspirate, sputum 
 

 
  

 
 

2 
 

 
2 - 3 

 

 

 

pigs by humans [News Report, 2009]. Swine flu virus 

spreads by direct or indirect contact among pigs by 
aerosols and remains asymptomatic there. High morbidity 

and low fertility rate is observed in case of swine flu. 
 

 

SYMPTOMS 

 

Swine flu shows clinical symptoms similar to seasonal flu 
and acute upper respiratory tract infection. The extent of 
this disease in humans is still unknown due to the escape 
of mild or asymptomatic case from recognition. An 
algorithm has been drawn up by the Health Protection 
Agency in the UK as to how they intend to assess the 
people suffering with swine flu. Geography is the first 
point on the algorithm according to which disease activity 
is seen in people coming from the same area. This 
obviously includes parts of the US but chiefly Mexico.  

The US Centres for Disease Control and Prevention 
(CDC) noted that although the virus was very serious but 
the world wide cases were usually mild. CDC noted that 
the hospitalizations and deaths had been of persons that 
had underlying weekend immune system conditions, 
heart diseases, asthma, diabetes or obesity 
(Pakspectator, 2009). According to symptom algorithm it 
is a temperature of 38 degrees or a history of a 
temperature of 38 degree not only respiratory symptoms 
e.g. runny nose or a headache, fever, cough, sore throat, 
body aches, chills, fatigue, but also diarrhea and vomiting 
have been observed in some cases. Emergency warning 
signs in children and adults are thus highlighted. 
 

 

In children 

 

Fever with rash, fast breathing or breathing trouble, bluish 

skin color, not drinking enough fluids, unbearable 

irritability in children, not waking up or interacting, flu-like 
symptoms improve but return with fever and cough. 
 

 

In adults 

 

Shortness or difficulty in breathing, Pressure or pain in 

abdomen or chest, sudden dizziness, confusion, persis-

tant or severe breathing, flu-like symptoms improve but 

 
 

 

return with fever and cough (CDC, 2009). 

 

VULNERABLE GROUP OF PEOPLE 

 

Vulnerable group of people includes pregnant women, 
care takers of less than 6 months old infants, health care 
workers, adults with Asthma and diabetes and people 
with immune-compromised systems. In a worst case 
scenario, 40% of the workforce are estimated by CDC 
might be unable to work at the peak of pandemic (Los 
Angeles Times, 2009). 
 

 

SPREAD OF SWINE FLU VIRUS 

 

The actual transmission is from pig to pig but swine flu 
virus can also jump from pig to human and once in 
human, it can spread from human to human very easily 
through coughing, sneezing, touching nose, mouth or 
contaminated surfaces. Currently H1N1 flu has been mild 
for most people; however it should not disregard the 
epidemic mild as is expected to come back and spread. 
Everyone should be vaccinated against swine flu; 
however the vaccine will become available in batches 
and the entire population cannot be vaccinated at once. 
Table 2 shows the various techniques used in the 
laboratory for the diagnosis of swine influenza. 

 

Global spread of swine flu 
 

Until 16
th

 April, 2010, worldwide more than 209 countries 

and overseas territories or communities have reported 
laboratory confirmed cases of pandemic influenza H1N1 
2009, including at least 17,798 deaths. Table 3 describes 
the deaths caused by swine flu in the world. 

 

Swine flu in Pakistan 
 
In Pakistan, National Centre of Excellence in Molecular 
Biology has detected 3 cases out of 77 suspects while 
Khan Laboratory Multan has detected 3 cases out of 7 
suspects. Total confirmed cases detected, using real-time 
PCR on WHO recommended kit, are 6 out of 84 suspects 
and out of these only 2 deaths have been reported until 

16
th

 April, 2010 (Idrees, 2010). 



   

Table 3. Deaths caused by swine flu in the world.    
    

Region Deaths*  

WHO regional office for Africa (AFRO) 168   

WHO regional office for the Americas (AMRO) At least 8274  

WHO regional office for the Eastern Mediterranean (EMRO) ** 1019   

WHO regional office for Europe (EURO) At least 4776  

WHO regional office for South-East Asia (SEARO) 1757   

WHO regional office for the Western Pacific (WPRO) 1804   

Total* At least 17798   
 

*The reported number of fatal cases is an under representation of the actual numbers as many deaths are never tested or 

recognized as influenza related. **No update since 7 March 2010 [Pandemic (H1N1) 2009, 2010]. 
 
 

 

PREVENTION AND CURE 

 

Vaccination 

 

There are generally two kinds of vaccines, 1) Inactivated 
virus vaccine and; 2) Live attenuated vaccine (LAIV). In 
August 2009, no vaccine was thought to be available 
before the end of 2009 by WHO. Influenza virus changes 
quickly and it was thought that if virus mutated further 
then it could be more virulent and less susceptible to any 
new vaccine. When WHO declared the new H1N1 swine 

flu as the first pandemic of the 21
st

 century on June 12
th

, 

a day after this declaration, Novartis AG (Swiss 
Pharmaceutical Company) announced the successful 
production of first batch of swine flu vaccine that was 
ready for sale in October, 2009. 
 

 

Vaccination planning 

 

More than 30 countries have asked Novartis to supply 
them with a swine flu vaccine. According to WHO several 
other drug makers have vaccine approved and ready for 
sale since September 2009 and CDC has already 
developed a vaccination plan. 
 

 

Who should be vaccinated first? 

 

The Public Health Agencies should work on priority list, 
deciding where the first batches should go. Several 
articles have been published showing that, unlike 
seasonal flu, the new H1N1 flu strains attack younger 
people and new pandemic strain tend to be more deadly 
in younger patients as S-OIV infection can cause severe 
acute respiratory distress syndrome and death in young 
to middle aged (Rogelio et al, 2009; Chowell et al., 2009; 
MMWR, 2009). The descendants of the 1918 flu have 
genetically modified themselves to be better able to sur-
vive and spread (CDC, 2009; MMWR, 2009). Therefore 
young people should be vaccinated first when a vaccine 

 
 
 

 

becomes available. It would protect not only them, but 
them, but also unvaccinated adults.  

Second group on priority should be health workers as 
they need to be protected from infection by the virus. 
According to the morbidity and mortality weekly report a 
sample of 26 health-care workers found that half became 
infected while at work (CDC, 2010). Next priority should 
be given to countries where the infection is more severe 
such as Mexico. Patients with chronic obstructive 
pulmonary disease, disease of the heart, and other parts 
of the body should be put on vaccination list before get 
vaccinate the whole population. 
 
 
 

Antiviral medications 

 

CDC has issued recommendations for clinicians on the 
use of antiviral medications for the prevention and 
treatment of swine flu. There are two classes of 
medicines available which are effectively used in some 
countries for the prevention and treatment of the disease,  
1) Adamantanaes (amantadine and remantadine), and 
inhibitors of influenza neuraminidase (oseltamivir and 
zanamivir). Swine flu virus developed resistance against 
amantadine and remantadine but are sensitive to 
oseltamivir and zanamivir. There are insufficient 
recommendations on the use of antivirals in the treatment 
and prevention of swine flu virus infection. Based on 
virus’ susceptibility profile national and local authorities 
are recommending to use oseltamivir and zanamivir for 
the treatment and prevention of disease (CDC, 2010). 
FDA has authorized emergency use of Oseltamivir 
(Tamiflu ®) and Zanamivir (Ralenza®) under certain 
circumstances not included in FDA-approved uses or 
outside the FDA-approved uses in response to the 
declaration of public health emergency involving 2009 
H1N1 influenza A virus made by Secretary of Health and 
Human Services on April 26, 2009 (Pan American Health 
Organization, 2009). In addition, FDA has recently issued 
intravenous drug (Paramivir) for the treatment of swine flu 
in certain hospitalized adults and pediatric patients. 



 
 
 

 

Other preventive measures 

 

First prevention is to keep the infected children at home. 
Children showing flu symptoms should be monitored; 
they may not have swine flu but can develop it. Home 
treatment remedies including adequate liquid intake and 
rest, soup to ease congestion, aspirin intake for instance 
and antiviral drugs may help in the treatment of infection. 

An updated guidance for employers of all sizes was 
developed by the US Department of Health and Human 
Services (HHS) and the Centres for Disease Control and 
Prevention (CDC) with input from the US Deapartment of 
Homeland Security (DHS) to use in response to 2009 
H1N1 flu. To slow down the spread of infection, air line 
passengers in Asia and other countries were quarantined 
with flu symptoms while some countries pre-screened 
passengers.  

Disease can also be prevented by having no contact 
with pigs. Initial screening and then activating various 
molecular tests, using tests that can detect the genetic 
material of the virus are seen to be useful for the early 
diagnosis of swine flu. Swine flu virus can be killed by 
cooking the pig meat at 70°C and not transmitted through 
properly cooked pig meat (Press release, 2009). So 
properly cooked pig meat is safe to eat (WHO, 2009). 
People getting flu are recommended to stay at home from 
work or school and to avoid crowds to avoid spread of 
virus further. Facial masks are of little use and may 
benefit in case of close contact with infected people but 
can’t replace other precautions because they are not 
designed to filter viruses and other biological agents 
(Mayo Clinic, 2009). Swine flu can be prevented by 
proper hand washing, balanced diet with fresh fruits and 
vegetables, whole grains and lean protein, sufficient 
sleep, regular exercise and avoiding crowds. 
 

 

IS THE SWINE FLU A LARGE MEDICAL SCANDAL OF 

21
ST

 CENTURY? 
 

It is said that swine flu is a large medical scandal of 21
st

 

century. Whether it is true or not, this is a contradictory 
matter. The purpose of this article is just to provide 
information to the readers. 
 

 
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