Mexicaans instituut vertelt over varkensgriep

Nieuws | de redactie
4 mei 2009 | Microbiologe Celia Alpuche leidt het Mexicaanse laboratorium, dat de varkensgriep als eerste op het spoor kwam. Zij vertelt exclusief over de 'gekte' en de problemen die de epidemie voor haar en haar Instituto de Diagnóstico y Referencia Epidemiológicos (InDRE) oplevert. "Some days we're getting two hours sleep and then a nap of half an hour. And there's Latte. Double shots. Espresso."

Alpuche: On April 7, we heard that the National Institute of Respiratory Disease was having unusually severe cases of pneumonia in young adults who were previously healthy. Immediately, we started to get the data around this cluster. We also started to do a retrospective analysis of the influenza data we had.

We looked at all data that we had regarding influenza detection since January up to this month and also to compare to the past season of influenza. In addition to the unusual pneumonia, we started to have rumors there were other cases that were not pneumonia, it was like a respiratory disease, an influenza-like illness.

Science: Did you see anything from your analysis of influenza trends that told you anything?

Alpuche: The first thing that it told us is that we were still detecting influenza in the country, not just in Mexico City. It was pretty much the same as we see every year except it was a prolongation of the flu season. Then we analyzed the subtypes of the strains of influenza, and one of the unusual things we saw was that in this season, we had the first peak in the last part of November and December and another one in February. Over the season, we started having more influenza B than we had the year before.

Science: Which had nothing to do with this outbreak.

Alpuche: Nothing to do with this. It was very confusing. We found that 37% of cases were B and the year before we only found up to 15% were B. Then we looked at data that they have in the influenza surveillance system at CDC to see if were having something unusual. We saw also in United States something kind of similar–a prolonged period of influenza and increases of strain B. So we thought that we were having something related to influenza, and we were still concerned about the pneumonia cases. We went back immediately to look at all the influenza outbreaks we had in the country since the season started to see if this was more related to the prolonged influenza or there was something else we were seeing. We had small outbreaks in some states in the central part of Mexico, Tlaxcala, and then the last outbreak we had was in Veracruz state, in the town of La Gloria, near Perote. That was in the last 2 weeks of March.

Science: Why didn’t that trigger concern in the last 2 weeks of March?

Alpuche: It was influenza-like illness, no fatalities and no pneumonia cases. This outbreak was deeply studied with state epidemiologists. The secretary of health of Veracruz did a wonderful job during the outbreak in the last 2 weeks of March.

Science: What capability did they have for typing subtypes?

Alpuche: The influenza, laboratory-based surveillance network in Mexico is using immunofluorescence–that’s the screening test, and it’s using antibodies against A and B. So that’s what the public health state lab is doing.

Science: So they don’t have subtype tests and had to refer the samples to you?

Alpuche: Yes. Not immediately, because if there’s nothing unusual, they wait to get accumulated cases and then send to the national referral center. One of the interesting things in this outbreak is they were testing, but the onset of symptoms was after 4 or 5 days. The sensitivity of the immunofluorescence test is low after 72 hours. Most of the tests, which were nasopharyngeal swabs, were negative.

Science: You later did more sampling from La Gloria, right?
Alpuche: In the last part of the outbreak in La Gloria, children started having symptoms April 1. They took the samples April 3. They sent the samples to the public health state lab, and they were processed April 4. These arrived at my lab on April 8.

Science: What were the positive ones?

Alpuche: They only identified three influenza strains at the end of the period. One turned out be H3N2. The other was A, but it was not heartening. Here at our lab, we were considering that it could be H1, but it looked indeterminate. To be honest, we were not able to type it. And then we had a B.

Science: The one that you weren’t able to type, did you send that anywhere else? Were you concerned that you couldn’t type it?

Alpuche: At that moment, we didn’t have any information about the untypeable A’s that they saw in the California children.

Science: On April 12, Mexico notified the Pan American Health Organization as per the International Health Regulations about the influenza-like outbreak in Veracruz. Initially, did you think these cases looked like influenza?

Alpuche: No, our initial thinking, as we reported according to the International Health Regulations, was that we were having intensification and prolongation of the influenza period. We thought the outbreaks of Tlaxcala and Perote were nothing unusual in terms of the pneumonia. Those were later on, and then we started to consider that there was something unusual.

Science: On 17 April, Mexico started to increase its surveillance for influenza. What triggered the switch to enhanced, active surveillance?

Alpuche: We got a notification of an isolated case, a 37-year-old woman, diabetic, who died because of respiratory disease and pneumonia in Oaxaca. The woman had onset of symptoms April 4. There was no connection at all with Perote. We got samples, and it was a lung biopsy because the relatives didn’t allow an autopsy. They intensively investigated the contacts around these deaths. They found some with respiratory diseases but no fatalities. Nothing unusual, okay? They were tested, and all were negative for influenza and other viruses.

Science: When did you first contact Frank Plummer, head of the National Microbiology Lab at the Public Health Agency of Canada?

Alpuche: I contacted him April 17 by e-mail, and he answered immediately. He wanted to know more about this, and we had a long conversation on Saturday, April 18.

Science: Frank told me that he initially didn’t think influenza. He thought it would be an unknown pathogen.

Alpuche: Exactly. And we discussed that with Dr. Plummer. In fact, I was the one who called him because I’m the lab person. I met him through the Global Health Security Action Group. And we’ve been talking about different collaborations, and immediately when we began discussing this and the epidemiology, we wanted to rule out everything we could.

Science: Why did you contact him?

Alpuche: Canada had a lot of experience with the screening of the severe acute respiratory syndrome, SARS, of unknown pathogenesis.

Science: What do you think of the criticism that Mexico didn’t do enough earlier on to catch this? It’s coming from both the Mexican press and the international press.

Alpuche: There’s always going to be something to find guilty people in everything. This is a new, unknown virus. We’ve been growing so much in terms of diagnostics and epidemiological surveillance lately. We still have limitations, that’s for sure. We really need to accept that. And we’re working very hard to overcome those limitations. We, along with all the health authorities, did everything possible to try to define this as soon as possible.

We’re working so hard to try and control this. And we were very open since the beginning. When I received the confirmation from Dr. Frank Plummer, I was immediately in contact with my superior Dr. Mauricio Hernández, and he spoke immediately with Secretary Córdova and he was basically open.

Science: Many laboratories in Mexico City I’ve visited are very sophisticated. What are the limitations that prevented your lab from identifying the new H1N1? What did CDC and Canada have that you didn’t have?

Alpuche: The only place in Mexico doing subtyping is this lab here. We are able to sequence and subtype, but we are overwhelmed with samples of influenza and other things from all around the country. It’s a little bit slower than in the U.S. or Canada.

Science: But what were the limits in your lab to isolate the virus and sequence it?

Alpuche: Since this week, we have experts from CDC and Canada helping us to set up a real-time PCR [polymerase chain reaction] technology to test for swine H1N1 directly.

Science: Is your lab the only lab in the country at this point that can do the confirmatory test with the real-time PCR machines?

Alpuche: At this point, yes, but we’re working with CDC and Canada to train molecular biologists in different institutions in six different states in Mexico. We have two real-time PCR machines we were able to get immediately–we borrowed one from the company. And now we bought 10 more machines. We are working full-time to speed up the diagnostics.

Science: How many samples do you have waiting to be tested?

Alpuche: Right now, we have a backlog of around 1000 tests that we’re rushing to do on time. We’re having three shifts of people working, during the morning, afternoon, and overnight.

Science: You have 1000 samples waiting to be tested, but there are nearly 2000 suspected cases.

Alpuche: Not all of the cases that were tested at the hospitals had samples that were referred to us. And not all of the 1000 samples we have are suspected cases.

Science: Are you still sending samples to CDC and Canada?

Alpuche: Yes, we sent more samples to Canada this week, and we are just arranging with the person here from CDC to send more samples to CDC. We want to rule out all these samples we’re holding so that we can keep going with the new ones.

Science: A lot of Mexican press and now press outside of Mexico has written about La Gloria and the large pig farm in nearby Perote, Granjas Carroll. There are all these allegations and even conspiracy theories.

Alpuche: I don’t know, there are so many rumors.

Science: What about the boy in La Gloria who has received so much attention?

Alpuche: It was mild disease, no problem.

Science: One of the theories is that this originated in the United States or elsewhere and a human came to Mexico, possibly a migrant. The assumption that it was a big pig farm could be very misleading.

Alpuche: Could be. That’s the same thought we have. We need more data to prove it. One of the interesting thing is, we’re seeing these cases isolated in Oaxaca and Perote, they are well-known for migration. And also the other state that we’re seeing several cases now during the active epidemic is San Luis Potosí, and it’s like the corridor for migration. It’s hard to believe that it’s going to be associated with this farm, but I know that the authorities are thoroughly investigated it.

Science: Do you think if this surfaced somewhere other than Mexico it would have been contained, or does influenza just move too quickly anyway?

Alpuche: Considering it was the end of the season, maybe that confused the fact a little that something else could grow, but probably influenza moves too quickly anyway.

Science: The United States detected cases very early, and the United States was not able to contain it. It tells me that the virus is smarter.

Alpuche: Yes, that’s for sure.

Science: One last thing. How many hours a night are you sleeping.

Alpuche: [laughter] At the most two.

Science: This has been going on for 2 weeks now.

Alpuche: Yeah, so some days we’re getting 2 hours and then a nap of half an hour. And there’s Latte. Double shots. Espresso.

Science: Anything you need, anything right now from the international community?

Alpuche: We’re okay now in the way we’re working, and our collaborators. But at some point if we need it for sure I’ll ask. But now, we’re okay.

[bron: AAAS – ScienceInsider]

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