The Risks Of Chikungunya Outbreaks In The United States

 

Credit Wikipedia

# 6855

 

 

Chikungunya, up until about a decade ago, was a little known mosquito-borne disease first described in Tanganyika in the early 1950s. For the next five decades it was sporadically seen across eastern and central Africa.

 

That is, until 2005, when Chikungunya made a surprise jump to the Indian Ocean island of Réunion. There, it infected nearly 1/3rd of the island’s 770,000 residents (see 2006 EID article Chikungunya Disease Outbreak, Reunion Island) in just a matter of months.

 

Chikungunya typically produces a fever, severe muscle and joint pain, and headaches. The symptoms usually go away after a few weeks, but some patients can sustain permanent disability, and some deaths have been reported.

 

In the eight years since that  jump, `Chik’ has spread further across the Indian Ocean, Southeast Asia, and even briefly into northern Italy.

 

While the virus isn't normally found in Europe, the vector, the Aedes mosquito, is.  All it took was one infected traveler to arrive infected with the virus to start the chain of transmission.

 

 

I told the story several years ago in It's A Smaller World After All, but the short version is that a traveler, returning from India, brought the virus to Italy in 2007 which led to more than 290 cases reported in the province of Ravenna, which is in northeast Italy.

 

The concern is that the same sort of introduction could happen elsewhere in Europe, or here in the United States, just as we saw with West Nile Virus in 1999 (see DVBID: Final West Nile Report For 2012) and with Dengue Fever in 2010 (see MMWR: Dengue Fever In Key West)

 

The two primary mosquito vectors of Chikungunya are the Aedes aegypti and Aedes albopictus (cite WHO FAQ) both of which can be found across many regions of the Americas.

Aedes albopictus (Asian Tiger) Mosquito - Wikipedia

Dark blue: Native range
Dark green: introduced (as of December 2007)

 

The risk is considered great enough that early last year, the CDC and PAHO (Pan American Health Organization) put together a 161-page guide on preparing for the arrival of Chikungunya to the Americas (see Preparedness and Response for Chikungunya Virus Introduction in the Americas).

 

All of which serves as prelude to a report that appeared last month in PloS Neglected Tropical Diseases called:

 

Modeling Dynamic Introduction of Chikungunya Virus in the United States

Abstract (reparagraphed for readability)

Chikungunya is a mosquito-borne viral infection of humans that previously was confined to regions in central Africa. However, during this century, the virus has shown surprising potential for geographic expansion as it invaded other countries including more temperate regions.

 

With no vaccine and no specific treatment, the main control strategy for Chikungunya remains preventive control of mosquito populations. In consideration for the risk of Chikungunya introduction to the US, we developed a model for disease introduction based on virus introduction by one individual. Our study combines a climate-based mosquito population dynamics stochastic model with an epidemiological model to identify temporal windows that have epidemic risk. We ran this model with temperature data from different locations to study the geographic sensitivity of epidemic potential.

 

We found that in locations with marked seasonal variation in temperature there also was a season of epidemic risk matching the period of the year in which mosquito populations survive and grow. In these locations controlling mosquito population sizes might be an efficient strategy.

 

But, in other locations where the temperature supports mosquito development all year the epidemic risk is high and (practically) constant. In these locations, mosquito population control alone might not be an efficient disease control strategy and other approaches should be implemented to complement it.

 

Our results strongly suggest that, in the event of an introduction and establishment of Chikungunya in the US, endemic and epidemic regions would emerge initially, primarily defined by environmental factors controlling annual mosquito population cycles. These regions should be identified to plan different intervention measures.

In addition, reducing vector: human ratios can lower the probability and magnitude of outbreaks for regions with strong seasonal temperature patterns. This is the first model to consider Chikungunya risk in the US and can be applied to other vector borne diseases.

(Continue . . . )

 

More background on this modeling study is available from the Cornell University Press Office.

 

 

Chances seen rising for chikungunya outbreaks in NYC, Atlanta, Miami

ITHACA, N.Y. – Global travel and climate warming could be creating the right conditions for outbreaks of a new virus in this country, according to a new Cornell University computer model.

 

The model predicts that outbreaks of chikungunya, a painful virus transported by travelers and spread by the invasive Asian tiger mosquito, could occur in 2013 in New York City during August and September, in Atlanta from June through September, and year-round in Miami. The probability of a disease outbreak is correlated with temperature, as warmer weather allows the Asian tiger mosquito to breed faster and grow in numbers, according to the study published in the November issue of PLOS Neglected Tropical Diseases.

 

According to the simulation, there is a high probability of a chikungunya outbreak if a single infected person arrives in New York in July or August and is bitten by an Asian tiger mosquito. The risks are the same, but with wider time frames, for transmission in Atlanta and Miami, according to the paper.

 

Asian tiger mosquitoes were introduced to the United States in Texas in the 1980s; they are established up the East Coast into New Jersey and are rising in numbers in New York City. The aggressive mosquito outcompetes local varieties and transmits more than 20 pathogens, including chikungunya and dengue, said Laura Harrington, associate professor of entomology and the study’s senior author.

 

“The virus is moving in people, and resident mosquito populations are picking it up,” Harrington said.

 

The model estimates that with typical regional temperatures, a chikungunya outbreak in New York would infect about one in 5,000 people, said Diego Ruiz-Moreno, a postdoctoral associate and the paper’s lead author

 

“However, this number would increase drastically as temperatures rise due to climate change,” Ruiz-Moreno said.

(Continue . . . )

 

While this study focused on Chikungunya, much the same could be said about the potential for seeing Dengue, Malaria, or even Yellow Fever making inroads in the United States and Europe. 

 

In March of 2010 the journal  Eurosurveillance carried a series of articles on vector borne diseases and their potential to impact those living in Europe. One of the articles, Yellow fever and dengue: a threat to Europe? by P. Reiter, had these sobering comments about the future of vector-borne illnesses in Europe.

 

The history of dengue and yellow fever in Europe is evidence that conditions are already suitable for transmission. The establishment of Ae. albopictus has made this possible, and the possibility will increase as the species expands northwards, or if Ae. aegypti is re-established.

 

The epidemic of chikungunya in northern Italy in 2007 [8,49] confirms that Ae. albopictus is capable of supporting epidemic transmission, although laboratory studies indicate that the strain of virus involved was particularly adapted to this species [50,51].

 

Nevertheless, it is not unreasonable to assume that climatic conditions that permit malaria transmission will also support transmission of yellow fever and dengue, in which case transmission could extend into northern Europe [52].

 

Reason enough that if you live in - or are visiting  - a mosquito prone area, to remember to follow the `5 D’s’  (courtesy Florida Department of Health).

 

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Preparing For An Unwanted Arrival

 

 

 

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PAHO, the Pan American Health Organization, in partnership with the CDC, have put together a 161-page guide for preparing for the arrival of Chikungunya to the Americas.

 

Chikungunya is a mosquito borne alphavirus (similar to Australia’s Ross River Virus, and EEE), of East African origin, that typically produces a fever, severe muscle and joint pain, and headaches.

 

They symptoms usually go away after a few weeks, but some patients can retain permanent disability.

 

First described in the early 1950s in Tanganyika, it was only sporadically seen over the years in eastern and central Africa. That is, until 2005, when Chikungunya made a jump to the Indian Ocean island of Réunion.

 

In the seven years since that time, Chik has migrated to India, Indonesia, and much of south-east Asia.   It has even been imported into Italy.

 

I told the story several years ago in It's A Smaller World After All, but the short version is that a traveler, returning from India, brought the virus to Italy in 2007 which led to more than 290 cases reported in the province of Ravenna, which is in northeast Italy.

 

 

Many infectious disease specialists have expressed concerns that Florida – which has recently seen a return of Dengue fever after more than 5 decades – could one day face the establishment of chikungunya as well.

 

The two primary mosquito vectors of Chikungunya are the Aedes aegypti and Aedes albopictus, both of which can be found across many regions of the Americas.

 

Aedes albopictus (Asian Tiger) Mosquito

Dark blue: Native range
Dark green: introduced (as of December 2007)

 

 

Credit – PAHO

 

For more on all of this, excerpts from the press release from PAHO, and a link to the PDF.

 

PAHO, CDC publish guide on preparing for chikungunya virus Introduction in the Americas

 

The Pan American Health Organization/World Health Organization (PAHO/WHO), in collaboration with the U.S. Centers for Disease Control and Prevention (CDC), has published new guidelines on chikungunya, a mosquito-transmitted virus transmitted that causes fever and severe joint pain.  The Guidelines for Preparedness and Response for Chikungunya Virus Introduction in the Americas aims to help countries throughout the Americas improve their ability to detect the virus and be prepared to monitor, prevent, and control the disease, should it appear.

 

Hundreds of people who have traveled from the Americas to Asia and Africa in the past five years have become infected with the chikungunya virus. While the virus has not spread locally in the Western Hemisphere, experts say there is a clear risk of its introduction into local mosquito populations. Local transmission could occur if mosquito populations in the United States or elsewhere in the Americas became infected with the virus and began spreading it to people in that area.

(Continue . . . )

 

To download the guide, Preparedness and Response for Chikungunya Virus Introduction in the Americas select this link.

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Another Message Of Import

 

 

Note:  Google’s Blogger Platform experienced a prolonged outage Thursday-Friday and so I’ve been  unable to update this blog for a couple of days.

I’ll be on the road either later today or early tomorrow, and so it will be Sunday night or Monday morning before I’m back to my regular blogging schedule.

 

# 5554

 

Aedes albopictus (Asian Tiger) Mosquito

Dark blue: Native range
Dark green: introduced (as of December 2007)

 

 

In the UK (and much of Europe), Dengue, Chikungunya, Yellow Fever, and Malaria remain imported illnesses. These countries, while not mosquito-free, aren’t normally home to the species that readily transmit these serious tropical diseases.

 

But in recent years, one of these disease vectors – the Asian Tiger Mosquito - has made inroads into many temperate countries (including Italy, France, and the eastern half of the United States) increasing the likelihood of local transmission.

 

In fact, a Chikungunya outbreak occurred  – in all places – Northern Italy in 2007.

 

I told the story in It's A Smaller World After All, but the crux of the matter being that a traveler, returning from India, brought the virus to Italy which led to more than 290 cases reported in the province of Ravenna, which is in northeast Italy.

The UK’s HPA has this to say about the introduction of the Asian Tiger Mosquito to Britain.

The Asian Tiger Mosquito (Aedes albopictus) has been identified by the Health Protection Agency as an insect that could potentially arrive in the UK. If this were to happen and if the mosquito became established, then it could cause a greater biting nuisance and may become involved in the transmission of disease.

 

To date there have been no confirmed reports of the mosquito in the UK and the public health risk remains low. Suspected sightings occur every summer, but thus far have always been identified as the endemic species Culiseta annulata.

 

 

In March of 2010 Eurosurveillance carried a series of articles on vector borne diseases and their potential to impact those living in Europe. One of the articles, Yellow fever and dengue: a threat to Europe? by P. Reiter, had this to say about the future of vector-borne illnesses in Europe.

 

The history of dengue and yellow fever in Europe is evidence that conditions are already suitable for transmission. The establishment of Ae. albopictus has made this possible, and the possibility will increase as the species expands northwards, or if Ae. aegypti is re-established.

 

The epidemic of chikungunya in northern Italy in 2007 [8,49] confirms that Ae. albopictus is capable of supporting epidemic transmission, although laboratory studies indicate that the strain of virus involved was particularly adapted to this species [50,51].

 

Nevertheless, it is not unreasonable to assume that climatic conditions that permit malaria transmission will also support transmission of yellow fever and dengue, in which case transmission could extend into northern Europe [52].

 

In order for an epidemic of Chikungunya, Yellow Fever, Dengue, or Malaria to occur in a previously unaffected area you need a competent vector (the right species of mosquito), and you need the (usually repeated) introduction of the causative pathogen into the mosquito population.

 

As the above Eurosurveillance article points out - 1.2 million people who live in the UK visit the Indian subcontinent, with average stays of 29 days) and, after malaria, dengue infection is the second most frequent reason for hospitalisation after their return

 

These tropical viruses are continually being introduced back into the UK (and other countries), increasing the chances that at some point they could become transmitted to others by the local mosquito population.

 

Which brings us to a recent HPA (Health Protection Agency) report on the rapidly increasing number of imported Dengue cases into the UK.

 

Dengue fever cases double among UK travellers

11 May 2011

Reports of dengue fever, a mosquito-borne infection, have more than doubled in UK travellers from 166 reported cases in 2009 to 406 in 2010, according to new figures from the Health Protection Agency (HPA).

 

Dengue fever does not occur in the UK and the highest proportion of cases were associated with travel to India - 84 cases (21 per cent) and Thailand - 61 cases (15 per cent).

 

This increase in dengue reports is coupled with a 34 percent rise in the number of reported cases of chikungunya, another mosquito borne infection, which rose from 59 cases in 2009 to 79 in 2010. Nearly 50 per cent of these cases were associated with travel to India.

 

Both diseases are endemic in Asia and Africa and dengue is also common in many other parts of the world including South America, Central America and the Caribbean and the Western Pacific.

 

These imported cases aren’t just a concern for the UK, of course.

 

Last summer, the CDC has issued a Health Advisory via their HAN (Health Alert Network) primarily to inform health care providers of the possibility of seeing Dengue Fever in returning visitors from areas where the virus is being seen.

 

This is an official
CDC HEALTH ADVISORY

Distributed via Health Alert Network
Sunday, July 25, 2010, 22:35 EDT (10:35 PM EDT)
CDCHAN-00315-2010-07-25-ADV-N

Increased Potential for Dengue Infection in Travelers Returning from International and Selected Domestic Areas

Summary

Dengue virus transmission has been increasing to epidemic levels in many parts of the tropics and subtropics. Travelers to these areas are at risk of acquiring dengue virus and developing dengue fever (DF) or the severe form of the disease, dengue hemorrhagic fever (DHF).

 

 

The return of locally acquired dengue fever to Florida in 2009 after a 6 decade absence was no doubt due to repeated introductions of the virus by travelers coming from countries where the virus is endemic.

 

You can find the CDC MMWR report on the reemergence of Dengue in Key West HERE.

 

In mid-June of 2010 the MMWR came out with a new report on Travel Associated Dengue in the United States between 2006 and 2008.

 

This surveillance pre-dates the Key West outbreak, and as the study reports, `Clinically recognized cases of travel-associated dengue likely underestimate the risk for importation because many dengue infections are asymptomatic or mildly symptomatic’.

 

The link  is Travel-Associated Dengue Surveillance --- United States, 2006—2008.

The explosive growth of Dengue around the world is well illustrated by the following graph from the World Health Organization.

What this graph doesn’t indicate is another doubling of dengue cases has taken place over the past 5 years.  

 

For now, major outbreaks of Dengue, Chikungunya, Malaria, or Yellow Fever remain unlikely in the United States and Europe.

 

Conditions that are conducive to these kinds of epidemics, however, continue to evolve; Dense urban populations, climate change, increased international travel, and the expanding range of mosquito vectors.

 

So the advice offered by this week’s HPA announcement by Dr Jane Jones, head of the HPA's travel and migrant health section, is worth taking to heart:

 

"These figures demonstrate that the importance of taking precautions to avoid mosquito bites extends to protecting against other infections, not just malaria. Unlike for malaria where drugs can be taken to prevent infection, there is no such option available to prevent either dengue or chikungunya.

Although the overall risk of contracting a mosquito-borne illness in the United States remains very small, scattered cases of Dengue (along with West Nile, EEE, SLEV, and other rare arboviral threats) are why Florida health departments continue to urge people to remember to follow the `5 D’s’:

 

 

Good advice in Florida, and anyplace else mosquitoes can be found.

 

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Chikungunya & Reports Of Flaccid Paralysis In India

 

 

# 5329

 

 

An interesting (although possibly misleading) report appears in today’s Deccan Chronicle on Chikungunya (CHKV) infections and reports of new `polio-like’ acute flaccid paralysis (AFP) complications occurring in Tamil Nadu (southern India) and Andaman & Nicobar Islands (bay of Bengal) during 2010.

 

First the story, which openly suggests that CHKV has `gone rogue’ (presumably meaning: mutated to a more virulent form) – but in actuality provides very little evidence to support the notion.

 

Following that, I’ve some cites that indicate that these sorts of complications aren’t exactly new.

 

 

Rogue chikungunya attacks Chennai, docs for caution

February 21st, 2011

The government may have vehemently denied the presence of chikungunya in the state last year, but studies have found that the viral disease has begun to exhibit rogue symptoms. The ICMR's Regional Medical Resource Centre has analysed over 1,000 cases of the disease from Tamil Nadu and Andaman & Nicobar Islands, and found that patients with chikungunya suffered from polio-like symptoms of ‘flaccid paralysis.’

 

<SNIP>

 

“However, the disease seems to have taken on an unusual turn in 2010. Patients suffered neurological symptoms of short-term paralytic attacks. Once the spasm passed, they found that their limbs were left weakened. They were not able to use their limp arms and legs,” explained Dr Elango.

(Continue . . . )

 

This report goes on to state that the ICMR was studying the virus strain looking for mutations or genetic changes that might explain these new symptoms.

 

Admittedly, declarations of feared or suspected `viral mutations’ are nothing new to the Indian press (see here, here, and here) and so I tend to take these stories with a very large grain of salt.

 

Nevertheless, given the explosion in Chikungunya cases around the world since 2004, the emergence of a new, more virulent `rogue’ strain of CHKV capable of causing a `polio-like’ illness would be pretty big news.

 

And with viruses, mutations are always possible.

 

A hasty search turns up a number of references to flaccid paralysis as a symptom of Chikungunya, however, going back to at least 2006. 

 

 

Epidemiol Infect. 2008 Sep;136(9):1277-80.

Four cases of acute flaccid paralysis associated with chikungunya virus infection.

Singh SS, Manimunda SP, Sugunan AP, Sahina, Vijayachari P.

GB Pant General Hospital, Port Blair, Andaman and Nicobar Islands, Port Blair-744101, India.

Abstract

The recent epidemic of chikungunya fever (2005-2006) in India has affected millions of people. The Andaman and Nicobar Islands, an archipelago situated in the Bay of Bengal 1200 km from peninsular India, also witnessed an outbreak of chikungunya fever starting in July 2006 which affected thousands of people.

 

Chikungunya fever classically manifests as high fever, myalgia, arthralgia and arthritis and in a certain percentage of cases with maculopapular rashes. However, deviation from the classical clinical features of chikungunya fever was reported in the earlier and recent epidemics.

 

During the recent epidemic in the Andaman and Nicobar Islands we came across ten cases of flaccid limb weakness following symptoms and signs suggestive of chikungunya fever. In four subjects we confirmed the diagnosis of chikungunya virus infection by serological method (IgM ELISA method). This is the case report of those four subjects.

 

 

In Chikungunya Fever: An Epidemiological Review of a Re-Emerging Infectious Disease (J. Erin Staples, Robert F. Breiman, and Ann M. Powers) which was published in the Journal Clinical Infectious Diseases  in September of 2009, we learn:

 

During early epidemics, rare but serious complications of the disease were noted, including myocarditis, meningoencephalitis, and mild hemorrhage [8, 39, 42, 43]. From recent epidemics, further neuroinvasive complications have been recognized, including Guillan-Barré Syndrome, acute flaccid paralysis, and palsies [44–48].

(Citations below)

44. Chikungunya in paediatrics: epidemic of 2005–2006 in Saint-Denis, Reunion Island. Arch Pediatr 2008;15:253-62.

45. Guillain-Barré syndrome complicating a chikungunya virus infection. Neurology 2007;69:2105-7.

46. Neurological complications in chikungunya fever. J Assoc Physicians India 2007;55:765-9.

47. Chikungunya virus induced sudden sensorineural hearing loss. Int J Pediatr Otorhinolaryngol 2008;72:257-9.

48. Four cases of acute flaccid paralysis associated with chikungunya virus infection. Epidemiol Infect 2008;136:1277-80.

 

 

Convincing evidence that flaccid paralysis has been – on rare occasions - associated with CHKV infection prior to the past year.

 

While primarily associated with fever, rash, and arthralgias, the finding that CHKV should produce occasional neurological symptoms (including AFP) isn’t completely surprising.

 

Chikungunya is an alphavirus, after all; a genus that includes a number of mosquito borne encephalitis-producing viruses (e.g. Eastern Equine Encephalitis, Western Equine Encephalitis, Venezuelan Equine Encephalitis).

 

Acute Flaccid Paralysis (AFP) has also been observed on rare occasions in association with a number of other encephalitic infections, including West Nile Virus, St. Louis Encephalitis, Japanese Encephalitis, and enterovirus 71.

 

The article that appears in today’s Deccan Chronicle provides us with precious few details.

 

We are not told how many cases of AFP have been  detected recently among confirmed CHKV cases in Tamil Nadu, or whether the ICMR has actually found any molecular changes to the virus they’ve been looking for.

 

All of which leaves us little with which to gauge the actual significance of today’s news report. 

 

But changes to the virus or not, Chikungunya is a serious and growing concern around the world, and it even has the potential to spread to the Southern United States and parts of Europe.

 

 

 

Until more information is forthcoming on today’s story, for more on the Chikungunya virus and other arboviral threats, you may wish to revisit the following blogs:

 

India: Chikungunya & Eye Infections

Pathological Flyers

India: Deep In The Miasma

ASTMH: Dengue and Insect-Borne EIDs In The US

A Message Of Import

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India: Chikungunya & Eye Infections

 

 

 

# 5169

 

 

Although conjunctivitis has been associated with Chikungunya in the past, Indian media sources are reporting on the appearance of more serious eye problems among infected patients.

 

First a report from the Times of India, then some background on Chikungunya, and other reports of accompanying eye infections.

 

Chikungunya of the eye makes an appearance

Dec 21, 2010, 02.55am IST

CHENNAI: The chikungunya virus, which leaves people with severe pain in the joints, is now affecting the eye too. Several samples of eye serum sent from the Government Ophthalmic Hospital in Egmore have tested positive for chikungunya at the King Institute of Preventive Medicine.

 

"Medical journals have reported ocular manifestation of the virus. In most cases, people who reported the infection had high fever, joint pain and blurring of vision. We have sent samples to the lab. It requires a detailed study," said Government Ophthalmic Hospital superintendent Dr Vasantha.

(Continue . . . )

 

Indian doctors are warning Chikungunya patients who experience ocular problems (photophobia, pain, swelling, blurred vision) to seek out an ophthalmologist immediately.  

 

Chikungunya is a mosquito borne alphavirus (similar to Australia’s Ross River Virus, and EEE), of East African origin, that typically produces a fever, severe muscle and joint pain, and headaches.

 

They symptoms usually go away after a few weeks, but some patients can retain permanent disability.

 

First described in 1955 in Tanganyika, it was only sporadically seen over the years in eastern and central Africa.   That is, until 2005, when Chikungunya made a jump to the Indian Ocean island of Réunion.

 

In the five years since that time, Chik has migrated to India, Indonesia, and much of south east Asia.   It has even been imported into Italy.

 

I told the story in It's A Smaller World After All, but the crux of the matter being that a traveler, returning from India, brought the virus to Italy in 2007 which led to more than 290 cases reported in the province of Ravenna, which is in northeast Italy.

 

 

Many infectious disease specialists have expressed concerns that Florida – which has recently seen a return of Dengue fever after more than 5 decades – could one day face the establishment of chikungunya as well.

 

While the Indian media reports over the past couple of days suggest these ocular manifestations are something new, a quick search of the literature shows that rare, but documented cases of retinitis, optic neuritis (inflammation of the optic nerve), and acute iridocyclitis have all been associated with Chikungunya infection in the past.

 

Ophthalmology. 2008 Feb;115(2):287-91.

Ocular manifestations associated with chikungunya.

Mahendradas P, Ranganna SK, Shetty R, Balu R, Narayana KM, Babu RB, Shetty BK.

 

Arch Ophthalmol. 2007 Oct;125(10):1381-6.

Optic neuritis associated with chikungunya virus infection in South India.

Mittal A, Mittal S, Bharati MJ, Ramakrishnan R, Saravanan S, Sathe PS.

 

Indian J Ophthalmol. 2009 Mar-Apr;57(2):148-50.

A case of bilateral presumed chikungunya neuroretinitis.

Mahesh G, Giridhar A, Shedbele A, Kumar R, Saikumar SJ.

 

 

So the real question would appear to be – just how prevalent are these reported chikungunya-related eye infections?

 

And we don’t seem to get an answer to that in these reports.  `Several’ is as close to quantifying the number of cases as it comes.

Until we have some solid numbers (total cases, # of cases with serious eye involvement, more lab results), this article – while certainly interesting – doesn’t really tell us if anything is new or has changed with the virus.

 

But I promise, we’ll keep an eye on it.

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