Swine flu worse in Mexico than US, but why?

(AP) -- Why has the swine flu engulfing Mexico been deadly there, but not in the United States?

Nearly all those who died in Mexico were between 20 and 40 years old, and they died of severe from a flu-like illness believed caused by a unique virus.

The 11 U.S. victims cover a wider age range, as young as 9 to over 50. All those people either recovered or are recovering; at least two were hospitalized.

"So far we have been quite fortunate," said Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention on Saturday, just hours before three new U.S. cases were confirmed.

Health experts worry about a flu that kills healthy young adults - a hallmark of the worst global flu epidemics. Deaths from most ordinary flu outbreaks occur among the very young and very old.

Why the two countries are experiencing the illness differently is puzzling public health experts, who say they frankly just don't know.

It may be that the bug only seems more deadly in Mexico.

And while experts believe Mexico is the epicenter of the outbreak, they're not certain if new cases are occurring or if the situation is getting worse. They also don't know if another virus might be circulating in Mexico that could be compounding the problem.

A big question is, Just how deadly is the virus in Mexico?

The seasonal flu tends to kill just a fraction of 1 percent of those infected.

In Mexico, about 70 deaths out of roughly 1,000 cases represents a fatality rate of about 7 percent. The Spanish flu pandemic of 1918-19, which killed an estimated 40 million worldwide, had a fatality rate of about 2.5 percent.

The Mexican rate sounds terrifying. But it's possible that far more than 1,000 people have been infected with the virus and that many had few if any symptoms, said Dr. Michael Osterholm, a prominent pandemic expert at the University of Minnesota.

U.S. health officials echoed him.

"In Mexico, they were looking for severe diseases and they found some. They may not have been looking as widely for the milder cases," said Schuchat of the CDC.

The U.S. health agency sent two investigators to Mexico on Saturday to help, she said.

Currently, even the counted illnesses are problematic. Only a fraction have been lab confirmed. Severe penumonia-like illness happens all the time, so it's challenging to figure out which ones are really tied to the outbreak, U.S. health officials said.

"These numbers need to be confirmed," said Dr. Richard Wenzel, the immediate past president of the International Society for Infectious Diseases.

Other ideas about the difference include:

-Genetic analysis of virus samples in the two countries is continuing. The CDC says tests results show the U.S. and Mexican viruses are essentially the same, but some experts have not ruled out the possibility that the virus is changing as it leaks across the border to the north.

-Perhaps nutrition levels are worse in some Mexican communities - poor nutrition can degrade a person's immune defenses, and make them more susceptible to illness.

-Air quality in Mexico City is considered terrible. That too may have affect patients confronted with a novel respiratory disease.

-Access to medical care has been an issue in Asia, where a rare bird - which does not spread easily from person-to-person - has killed more than 200 over the last several years. Maybe Mexican patients have also had trouble getting medical care or antiviral drugs, some have speculated - even though the government provides health care.

All that is speculation at this point.

"The question of why the appears to be more virulent in Mexico is one that we are looking intensively into," the CDC's Schuchat said. "Rather than speculate, it's important for the science to lead us on this."

Join PhysOrg.com on Facebook!
Follow PhysOrg.com on Twitter!

Associated Press Writer Mark Stevenson in Mexico City contributed to this report.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Citation: Swine flu worse in Mexico than US, but why? (2009, April 26) retrieved 20 October 2019 from https://medicalxpress.com/news/2009-04-swine-flu-worse-mexico.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Apr 26, 2009
What! A virus that changes!? No way! I thought evolution wasn't real! This must be a lie!

Apr 26, 2009
Couldn't possibly be because we dose our swine rather heavily with antibiotics.

H1N1 is an Influenza virus. Antibiotics only work against bacteria, not against viruses.
Antibiotics inhibit processes during replication. A virus isn't alive. It can't produce its own proteins, nor can it replicate. It uses a host cell to survive and reproduce. So you can't inhibit its growth with antibiotics, because by inhibiting the replication of the host cells you would also inhibit the growth of the other cells that make up our body.

Apr 26, 2009
What! A virus that changes!? No way! I thought evolution wasn't real! This must be a lie!

They do change, and change quickly compared to other "organisms", but generally not as fast as this.

Apr 26, 2009
They do change, and change quickly compared to other "organisms", but generally not as fast as this.

I know, the comment was meant to make fun of creationists..

Apr 26, 2009
They do change, and change quickly compared to other "organisms", but generally not as fast as this.

I know, the comment was meant to make fun of creationists..

I know, hence my response to try to keep us on topic instead of allowing bigoted asinine statements like that to pass...

Unless of course you can tell me wtf creationism has to do with this topic.

Apr 27, 2009
modernmystic-you and I have had our disagreements brotha, but I agree with you here believe it or not...what in the HELL does creationism have to do with this topic.

Oh wait...I know, the imaginary friend called "God" (ever notice it spells dog backwards btw...like you idiots have been dogged with lies all your life), must have "made" this virus to punish us humans.

I know the creationist comment was meant as a joke, but EVERY LAST ONE of us knows that mentioning the creationism MYTH will spark a long thread that entails religious morons defending their oh so true to heart bullshit beliefs upon each of us factual folks in here.

Ive known conservatives that hate, Ive know conservatives that are ignorant. But LuckyBrandon, Ive seldom met a liberal which isnt either ignorant or hateful, as these are the hallmarks of the left.

Apr 27, 2009
I was wondering if the residents could have lower levels of vitamin D due to the blockage of UVB radiation by sulfate aerosol pollution. If their vitamin D levels were very low this could help explain the apparent worse outcomes in Mexico.

Flu generally is far more common in periods of low vitamin D levels.

May 01, 2009
Did anyone consider that those who trace their ancestry back to the indigenous peoples of Mexico only have 500 years of history with pigs, while Europe, Africa, Asia, etc. have some 7,000 years of exposure to domestic swine? (Pigs first came to the New World on the ships of Spanish explorers) Isn't it possible that, after many millenia of being exposed to variants of swine flu--and having the more susceptible die off--that those who are left have better natural defenses? Those naturally selected may be more inhospitable hosts and, therefore, may experience a diminished response to this "new" virus (is it really new? Just because today's scientists never saw it before doesn't necessarily make it new). In the end, 7,000 years of natural selection on "Old World" humans is likely to have had profound effects that "New World" humans may never have experienced, and treatment modalities should be appropriately adjusted to ensure those who likely need the most help get the most help.

May 01, 2009
LuckyBrandon, since inherited resistance hasn't been shown to be a recessive trait, it's quite possible that being a hybrid provides you--and most Americans--with added protections. It would be interesting to see mortality data by population group--and focusing on peoples whose ancestors migrated here prior to the domestication of pigs. We've already seen that vacation patterns have driven the spread of the disease, with Europeans and Americans composing a majority of the visitors Mexico, but the small geographic distribution of deaths is worth exploring from a treatment perspective. Of course, the virus may have mutated into more benign forms, and only those who contracted the original--more virulent--form may be the only ones who die. That would be very good news because history is rife with examples of pathogens that mutate into more virulent forms with more diverse paths of infection.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more