Swine flu

Overview of swine flu

Viruses thrive in a wide range of environments and even in extreme climatic conditions. Hence the incidences of viral infections are common in different parts of the world. The inhabitants of the tropics and the subtropics are the potential victims of these infections. In such climatic zones, viral infections often lead to epidemic outbreaks. In the low and middle-income countries, viral infections are widespread due to the presence of a large immunocompromised population.

Swine flu is one such infection which at first occurs in pigs and then spreads to the humans. The prevalence rate of the disease is quite high in India. According to the reports of the World Health Organisation (WHO), over 31,156 positive test cases of swine flu have been reported in March 2015, in India. The death toll reached about 1841 in the same year.

What is swine flu?

 Swine flu or swine influenza or pig flu is a viral infection caused by one of the many types of influenza viruses.

The strains of influenza C virus or any of the subtypes of influenza A virus such as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3 may be responsible for the disease.

The disease occurs in the pigs in enzootic or epizootic form.

In enzootic form, the symptoms of the disease are not so prominent and the infection does not spread from the pigs to other animals or humans.In epizootic type, the virus completes all the phases of its life cycle within the body of the pig and presents with certain prominent symptoms.This form of infection is contagious. The symptoms are further augmented by secondary bacterial infections if any.

In human hosts, mainly respiratory symptoms are present. 100% morbidity rates are observed, although the mortality rates are relatively low. The incidence rate of swine flu is quite high in those countries where stray pigs are abundant or the people are used to having pork regularly.

How does swine flu transmit?

Swine flu is a highly communicable respiratory disease that readily transmits from one host to another. The commonly observed means of transmission are as follows-

• Pig to pig transmission: According to CDC, more than half of the breeding pigs are directly exposed to the swine flu virus. Therefore, a pig to pig transmission of the disease is very common. The direct contact between infected and healthy animals mainly occurs when all these animals are transported together to other places. Intensive farming, a type of farming where the pigs are bred very close to each other can lead to the spread of the infection through direct exposure. Respiratory droplets (aerosols) produced by the pigs during sneezing or coughing are also the carriers of the infectious viruses.
• Pig to human transmission: This is also called zoonotic transmission. People working in the poultries and the farmhouses are at greater risks of these diseases. Veterinarians and the meat processing workers are also at potential risks of this disease. Immunizations of all these workers with all strains of the influenza A and C viruses is necessary in order to protect them from swine flu or other similar diseases.
• Avian H5N1: Interaction with the avian H5N1 gene can cause swine flu. How it happens needs to be explained. Pigs are often infected with the strains of the influenza virus that can affect mainly three hosts- humans, pigs, and birds. This makes the pigs a site of exchange of genes between the different influenza viruses. These interactions produce more dangerous strains. Studies have shown that the H3N2 originally formed from the H2N2 by antigenic shift.

What are the main signs and symptoms of swine flu?

Swine flu produces a range of visible signs and symptoms in both pigs and humans. The signs observed in human beings will be discussed in details in this section. At the onset, the disease is marked by mild to moderate symptoms. These are as follows-

• Acute onset fever which is mostly intermittent in nature
• Constant cough
• Runny and congested nose
• Soreness in the throat
• Body aches and chills
• Headaches
• Extreme fatigue and general body weakness
• General malaise
• Diarrhoea and vomiting
• Pneumonia and respiratory failure

In the more progressive stages, the following symptoms are observed-

• Increased breathing rate
• Bluish or greyish discoloration of the skin
• Dehydration
• Constant sleeping
• Lack or loss of interaction
• Not waking up at normal times (in small children)
• Irritability (the child does not want to be held)
• Recurrent influenza-like symptoms
• Extreme tiredness
• A throbbing headache
• Nasal congestion
• A sore throat

What are the main types of swine flu?

Swine flu is classified according to the type of virus causing the infection, that is Influenza A and C. These are described below-

Influenza A: Four Influenza subtypes viz H1N1, H1N2, H2N3, H3N1 and H3N2 usually cause swine flu. Among all these, the H1N1 strain is the most prevalent. Studies have shown that the H3N2 originally formed from the H2N2 by antigenic shift.

Influenza C: Incidences of Influenza C infection is rare since it has a limited genetic diversity and a limited host range. Also, its host range is also limited.

What are the necessary diagnostic tests for detecting swine flu?

Swine flu has symptoms similar to that of common cold and flu and pneumonia. Hence a differential diagnosis is necessary to rule out these two diseases. In the next step, the following diagnostic tests may help-

• Real-time PCR
• Oropharyngeal swab test

The ongoing research works are being directed towards devising point-of-care tests for diagnosing swine flu patients.

How can you treat swine flu?

Oseltamivir medications are the best means of treating swine flu via prophylactic treatment. Chemo Prophylaxis is also one effective way of treating the disease. Other supportive therapies include administering intravenous fluids to compensate for the acute dehydration and oxygen therapies.

Prevention

Vaccinations can help prevent swine flu to some extent. But other protective measures to stay away from the virus should also be adopted. Proper diagnosis should be carried out in all cases to determine the exact cause of infection. Consultation with an expert must be done before resorting to self-medication, in order to avoid the side-effects caused by any over-the-counter drugs.

References