A few days ago, a Chilean biologist commented on an earlier post in this series (see the original discussion here) and I asked him if he would be willing to answer some questions from a scientist’s perspective and in a way that would go beyond the official statements issued by the Ministry of Health.
Pablo Astudillo, the biologist behind Astu’s Science Blog, agreed and here is our interview.
MS: My understanding is that the disease was originally thought to be the same Swine Flu that is commonly passed among pigs, but that the name has been changed to AH1N1 because it is in fact a human virus (from what I have read, only human viruses are classed as Type A and are not transmitted between humans and animals). Your comment left me wondering if it is a case of the same virus adapting/mutating from animal to human, or is it a case of more advanced research revealing that it had been misidentified originally?
PA: OK, from the beginning… The AH1N1 virus did not originate from humans or birds. This virus was born from a succession of events that allowed genetic material to be recombined (which means, in laymen’s terms, that several pieces of DNA are “copied and pasted”). These events can happen in many organisms in which two or more viruses are able to enter. Pigs have this characteristic; they present two specific receptors in the tracheal epithelium cells that are recognized by human and avian influenza viruses.
The AH1N1 virus originated in pigs in such a way, but was then transmitted to humans. This has been happening for a long time, and it is believed that events like this have been responsible for many pandemic influenzas, including the Spanish flu in 1918.
In theory, the AH1N1 virus can infect ANY animal with receptors that are able to recognize the virus in cells from the tracheal epithelium. I don’t know if cats and dogs have these receptors. One myth that has to be corrected is: this virus is not new… it is evolving constantly.
MS: You said that the majority of cases in Chile are asymptomatic… so how were they identified? If the flu produces no symptoms, is it dangerous? What is the greater concern about the transmission of asymptomatic diseases? Along the same line, will contracting the virus allow the person to develop immunities for a worse or related case of the flu?
PA: I am not familiar with the clinical features of the AH1N1 influenza, but some things can be discussed. As soon as Chile’s health authorities identify a person with AH1N1 influenza, they contact the relatives and friends who have been in touch with the infected person and run tests to determine whether they are positive for the virus. That’s why we have many positive asymptomatic cases.
The greater concern to authorities is, obviously, the public impact of having too many cases, especially when we are a few months from a presidential election.
For medical doctors, the concern is having an overloaded public hospital system. Santiago’s winter season is complicated; the cold, the viruses and the pollution create a scenario where many old people and children die from pulmonary diseases.
To scientists, the concern is with respect to the opportunity of the virus to evolve and develop a new mutation that can be dangerous to humans. Nonetheless, some evolutionary biologists claim that such viruses are quickly eliminated from the ecological niche because they kill their hosts. However, if a virus produces more than a cold and fever, obviously we have to be prepared.
Finally, indeed, becoming infected with this virus will allow humans to produce antibodies that can be useful in future infections. But if a new strain of the virus harbors a mutation in the protein recognized by the antibody produced, the said antibody is useless.
MS: You said the index case is the small boy with no known direct exposure. What does “index case” mean in laymen’s terms? What is the scientific concern here? From what I have read, flu viruses are transmitted through airborne contact; could he simply have sat next to the wrong person on the bus? Or are they concerned that there is another form of transmission that is not understood?
PA: In this case, the “index case” refers to the first patient identified. The virus is transmitted through contact, from saliva, sneezes, kisses, etc. But you should ask a medical doctor for detailed information. The virus does not fly through the air. I mentioned the concerns above.
MS: You say the public health system “claims” we are ready… do you agree? It sounds like you have your doubts…
PA: At this point, that question is irrelevant. We have 199 confirmed cases, making us the 5th country in the world** with more cases of AH1N1 influenza. The system claimed that “we are ready,” but the explosive increase in cases says otherwise. [**At the time this was posted, Chile had just dropped to 6th place.]
MS: Why, in your opinion, does Chile have so many cases? Apparently we are number 2 behind Mexico in Latin America. I wonder how much has to do with (1) more travel means more exposure (although I have no way to prove that Chileans travel abroad more than other Latinos), and (2) how much it has to do with more advanced methods of identification….
PA: Well… The authorities claimed that we had suffered the same as New York: we had infected children in schools. Children are more exposed to other children while in class, playing games, going to parties, etc. That explains the explosive increase in positive cases. The parents and relative of those children then quickly became infected.
In fact, a few days ago the authorities said that around 75% of the cases were children related with the outbreak in schools of Vitacura, Santiago. But with 199 cases, it is more difficult to establish relationships. My guess is that it has nothing to do with Chilean people traveling more often than other South Americans.
About the identification methods, one thing that Chilean authorities claimed was that we have more advanced and faster methods for detection of the virus. That’s a political lie. The diagnostic method is simple, fast, reliable, and, above all, a standard procedure in every university with biology or molecular biology laboratories. Claiming such a thing is not only a lie, but also a vain way to explain the irresponsibility of the authorities. As soon as the first cases were detected in schools, the authorities should have suspended school activities.
The Original Posts for Swine Flu in Chile:
May 28, 2009: AH1N1 (Swine Flu) in Chile: Update Part 4
May 22, 2009: Swine Flu in Chile Part 3: Update on Chile
April 29, 2009: Swine Flu in Chile Part 2: Update on Chile
April 28, 2009: Swine Flu in Chile Part 1: So far, so good