The New Nation - Internet Edition

Dr. Md. Alimul Islam

Swine flu (swine influenza) is a disease of pigs. It is a highly contagious respiratory disease caused by one of many Influenza A viruses. Approximately 1% to 4% of pigs that get swine flu die from it. It is spread among pigs by direct and indirect contact, aerosols, and from pigs that are infected but do not have symptoms. In many parts of the world pigs are vaccinated against swine flu. Most commonly, swine flu is of the H1N1 influenza subtype. However, they can sometimes come from the other types, such as H1N2, H3N1, and H3N2.

The current outbreak of swine flu that has infected humans is of the H1N1/A type - this type is very dangerous for human community of the world. The new swine flu virus that broke out in Mexico is unique and potentially dangerous in one way. It is a virus that has a combination of gene segments from human, bird and swine viruses, and can potentially become infectious in humans that have no immunity to the new strain.

Influenza viruses can change its make-up in one of two ways: Antigenic drift is a series of mutations that cause the virus to gradually evolve over time. Antigenic shift is an abrupt change in the surface antigen proteins that suddenly creates a new subtype of the virus. In the history of influenza outbreaks, antigenic shift is the cause behind pandemics in 1918 (Spanish Flu), 1957 (Asian Flu) and 1968 (Hongkong Flu) because the populations have not developed antibody protection against the virus.

What's especially unique about this new swine flu strain is that it's a type A/ strain H1N1 and it hasn't been previously detected in pigs.

The WHO announced they would refer to the new influenza virus as influenza A (H1N1) or "Influenza A (H1N1) virus, human" as opposed to "swine flu", also to avoid suggestions that eating pork products carried a risk of infection.

The outbreak has also been called the "H1N1 influenza," "2009 H1N1 flu," or "swine-origin influenza." However, Seth Borenstein, writing for the Associated Press quoted several experts who objected to any name change at all.

Avian flu and human seasonal flu viruses can infect pigs. The H3N2 influenza virus subtype, a virulent one, is thought to have come from pigs - it went on to infect humans. It is possible for pigs to be infected with more than one flu virus subtype simultaneously. When this happens the genes of the viruses have the opportunity to mingle. When different flu subtypes mix they can create a new virus which contains the genes from several sources - a reassortant virus.

Although swine influenza tends to just infect pigs, they can, and sometimes do, jump the species barrier and infect humans.

Outbreaks of human infection from a virus which came from pigs (swine influenza) do happen and are sometimes reported. Symptoms will generally be similar to seasonal human influenzas - this can range from mild or no symptoms at all, to severe and possibly fatal pneumonia.

As swine flu symptoms are similar to typical human seasonal flu symptoms, and other upper respiratory tract infections, detection of swine flu in humans often does not happen, and when it does it is usually purely by chance through seasonal influenza surveillance. If symptoms are mild it is extremely unlikely that any connection to swine influenza is found - even if it is there. In other words, unless the doctors and experts are specifically looking for swine flu, it is rarely detected. Because of this, we really do not know what the true human infection rate is.

Since the World Health Organization's (WHO's) implementation of IHR (2005) in 2007, they have been notified of swine influenza cases from the USA and Spain.

In March/April 2009 human cases of influenza A swine fever (H1N1/A) were first reported in California and Texas. Later other states also reported cases. A significant number of human cases during the same period have also been reported in Mexico - starting just in Mexico City, but now throughout various parts of the country. A total of more than 4600 people of 20 countries were affected and 176 people died due to this new strain of swine flu virus ( H1N1/A) .

How does a human catch swine influenza? From contact with infected pigs (most common way), from contact with infected humans (much less common way)

In cases when humans have infected other humans close contact was necessary with the infected person, and they nearly always occurred in closed groups of people.

If the pork meat and pork food products have been handled properly transmission of swine influenza to humans is not possible. Cooking pork meats to a temperature of 700C kills the virus. So the answer is YES, pork meat and pork food products are safe to eat after proper cooking by the people who eat pork.

As swine influenza infection among pigs is not an internationally notifiable disease we cannot be completely sure. Swine influenza infection among pigs is known to be endemic in the USA. Outbreaks have also occurred in other parts of North America, South American, Europe, Africa, China, Japan, and other parts of Asia.

People who are not in close contact with pigs generally have no immunity to the swine influenza viruses - they are less likely to be able to prevent a virus infection. If the virus infects enough people in a given area, the risk of an influenza pandemic is significantly greater. Experts say it is very hard to predict what impact a flu pandemic caused by a swine influenza virus would have on the global human population. This would depend on how virulent the virus is, what existing immunity among humans there already is, plus several other factors.

Flu pandemic come in waves. the 1889-1890 and 1918-1919 flu pandemic each came in three or four waves of increasing lithality. But within a wave mortality was quearter at the beging of the waves. According to the WHO pandemic aleart phase of the swine flu was 4 until April 27, 2009 and the aleart phase raised to 5 from April 29, 2009.

No - not for humans yet. It will take 3-6 months to prepare an effective vaccines against the new strain of swine flu virus.

Vaccination against influenza are most commonly given to high risk human industrilized country and to farm poultry. The most common human vaccine is the trivalent influenza vaccine that contains purefied and inactivated materials from the viral strains (Two from influenza A sub-types and One from influenza B virus strains). The vaccine formulated for one year may be in effective the following year. Since the influenza virus changes rapidly over the time.

We really don't know. Influenza viruses are adapting and changing all the time. If a vaccine was made, it would have to be specifically for a current strain that is circulating for it to be effective. The WHO says it needs access to as many viruses as possible so that it can isolate the most appropriate candidate vaccine.

The signs and symptoms of swine influenza in humans are similar to those of regular flu, and include: Muscle and joint pain, Chills, Cough, Diarrhea (less common), Terrible Headache, Sore throat, High rise of body temperature (fever), Tiredness (fatigue), Vomiting (less common)

There are some drugs around that can effectively treat swine flu infection in humans - and many types of flu infections in humans. There are two main types:

Inhibitors of influenza neuraminidase i.e. oseltamivir (Tami flu) and zanamivir (Relenza)

Most previous swine influenza human cases recovered completely without the need for medical attention. What one can do to protect oneself?, Washing of hands regularly with soap, Try to stay healthy Get plenty of sleep, Do plenty of exercise, Try to manage your stress, Drink plenty of liquids, Eat a well balanced diet, Refrain from touching surfaces which may have the virus, Do not get close to people who are at sick with swine flu virus, Stay away from crowded areas if there is a swine flu outbreak in your area, Stop traveling the swine flu affected (20) countries if it is not very urgent. If you feel bad after traveling from abroad please contact with the doctors for his advices

If you are infected, how can you stop others from becoming infected?, Limit your contact with other people, Do not go to work or school, When you cough or sneeze cover your mouth with a tissue. If you do not have a tissue, cover your mouth and nose. Put your used tissues in a waste basket, Wash your hands and face coughing and sneezing regularly, Keep all surfaces you have touched clean, Follow your doctor's instructions.

In 2007, scientists reported two cases of H2N3 influenza virus in pigs that have two gene segments from birds mixed with gene segments from common swine influenza viruses. This made H2N3 strain infectious and highly transmissible between pigs. Lab tests also showed that H2N3 can infect ferrets and mice.

According to the World Health Organisation (WHO), a pandemic can start when three conditions have been met: Emergence of a disease new to a population. Agents infect humans, causing serious illness. Agents spread easily and sustainable among humans.

A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not considered a pandemic, because the disease is not infectious or contagious.

WHO and CDC are concerned that this outbreak may become a pandemic for the following reasons: New strain (Never before seen strain of H1N1) of virus having no immunity against the virus to human, Possessing wide spread human-to-human transmission properties (young, adults of 25-45 years old), High virulence properties (due to cytokine storm), Lek of sufficient data.

Steps needed to be taken: Formation of monitoring cells for swine flu, Public awareness must be created through print and electronic media, by organising seminar and symposium; The Ministry of health and the Ministry of fisheries and livestock should work jointly to face the coming global threat of swine flu; Resource personnel from the Universities and Research Institutes should work jointly for greater interest of nation; Special fund should be allocated for this purpose in the next National budget; Internationally accredited laboratory (BSL-3) must be established to conduct research on Bird flu and Swine flu viruses in the country.

(The writer is professor and Head of the department of Microbiology and Hygiene, faculty of veterinary science, Bangladesh Agricultural University, Mymensingh)