Correspondence

Chikungunya Outbreaks

N Engl J Med 2007; 356:2650-2652June 21, 2007

Article

To the Editor:

In their Perspective article on outbreaks of chikungunya fever, Charrel et al. (Feb. 22 issue)1 suggest that the recent outbreak in India2 could have been caused by the same viral strain that caused the Indian Ocean outbreak.3 Recent data do not support this speculation.4,5 We previously described sequence microheterogeneity in the viruses causing the Indian Ocean outbreak.4 We have compared E1 sequences from viruses involved in the Indian and Indian Ocean outbreaks (Figure 1Figure 1Evolutionary Links among E1 Partial Sequences from Strains of Chikungunya Virus.).4,5 The strains differed only in a single nucleotide change (T321C), which was found in all Indian Ocean isolates. Isolates from India retained the ancestral T321 nucleotide present in all other African and Asian strains, making it unlikely that the outbreak in India was caused by a strain originating from the Indian Ocean outbreak. Nevertheless, in contrast to sequences from all other available chikungunya viruses, the Indian and Indian Ocean isolates shared two nucleotide changes: A306G and C384T. These shared derived characters indicate common ancestry. The strain isolated from Yawat, India, in 20005 retained the ancestral nucleotide at both positions but had a distinctive T468C change, arguing against a direct link between this strain and the strain implicated in the 2005–2006 Indian outbreak.

Sylvain Brisse, Ph.D.
Isabelle Iteman, Ph.D.
Institut Pasteur, 75724 Paris, France
sbrisse@pasteur.fr

Isabelle Schuffenecker, M.D., Pharm.D.
National Reference Center for Arboviruses, 69007 Lyon, France

5 References

1. 1

   Charrel RN, de Lamballerie X, Raoult D. Chikungunya outbreaks -- the globalization of vectorborne diseases. N Engl J Med 2007;356:769-771
   Full Text | Web of Science | Medline

2. 2

   Saxena SK, Singh M, Mishra N, Lakshmi V. Resurgence of chikungunya virus in India: an emerging threat. Euro Surveill 2006;11(8):E060810.2.
   

3. 3

   Higgs S. The 2005-2006 Chikungunya epidemic in the Indian Ocean. Vector Borne Zoonotic Dis 2006;6:115-116
   CrossRef | Web of Science | Medline

4. 4

   Schuffenecker I, Iteman I, Michault A, et al. Genome microevolution of chikungunya viruses causing the Indian Ocean outbreak. PLoS Med 2006;3:e263-e263
   CrossRef | Web of Science | Medline

5. 5

   Yergolkar PN, Tandale BV, Arankalle VA, et al. Chikungunya outbreaks caused by African genotype, India. Emerg Infect Dis 2006;12:1580-1583
   CrossRef | Web of Science | Medline

To the Editor:

I am concerned about the accuracy of the Perspective article by Charrel et al. regarding the distribution of Aedes albopictus in Australia and the number of deaths attributed to chikungunya in the recent outbreaks on Indian Ocean islands. The map that accompanies the article indicates that A. albopictus is widespread in Australia. This is incorrect. A. albopictus has not been found on mainland Australia.1

In April 2005, A. albopictus was discovered in the Torres Strait of Australia.2 However, an eradication program is currently restricting any further progression into the mainland. The map also fails to indicate that A. albopictus is present in much of western Indonesia, whereas it shows populations in most of the western United States.

I am also concerned about the statement that chikungunya was “implicated in 237 deaths.” The National Arbovirus and Malaria Advisory Committee believes that much of the data on human deaths attributed solely to chikungunya are very contentious and have not been properly evaluated.

Julie Hall, M.P.H&T.M.
National Arbovirus and Malaria Advisory Committee, Canberra CT 2601, Australia
julie.hall@health.gov.au

2 References

1. 1

   Gratz NG. Critical review of the vector status of Aedes albopictus. Med Vet Entomol 2004;18:215-227
   CrossRef | Web of Science | Medline

2. 2

   Ritchie SA, Moore P, Carruthers M, et al. Discovery of a widespread infestation of Aedes albopictus in the Torres Strait, Australia. J Am Mosq Control Assoc 2006;22:358-365
   CrossRef | Web of Science | Medline

Author/Editor Response

Brisse et al. contribute a new phylogenetic tree that includes strains involved in the chikungunya outbreaks in 2005 and 2006. Their data confirm that strains implicated in both the Indian Ocean and Indian outbreaks originated from a common ancestor that has not yet been identified. Moreover, they show that the current Indian outbreak involves a different strain from that found in Yawat, India, in 2000. This suggests that the huge outbreak of 2005–2006 followed the appearance of a new variant that subsequently evolved in India and the Indian Ocean.

Hall may be right to emphasize that the mosquito A. albopictus is not established in mainland Australia. However, it is established in the Torres Strait region in northern Australia1 and has been repeatedly identified in Australian and New Zealand harbors for the past 20 years.2,3 Hall is also concerned about the reported number of deaths. The number of deaths per month on Reunion Island increased by 34% in February 2006 and 25% in March 2006, as compared with the number in the same month in 2005.4 These increases represent a total of 170 to 180 additional deaths, just for these 2 months, with many of them in patients older than 75 years. A total excess of 260 deaths was reported by the French National Institute for Public Health Surveillance4 for the outbreak. This corresponds roughly to a 1% case fatality rate for estimated cases of chikungunya (based on seroprevalence studies). Indeed, the disease outbreak paralleled a significant increase in mortality, and no other cause of death was identified during this period. Few outbreaks have modified significantly the death ratio for a whole country. In the Reunion outbreak in 2006, chikungunya was a significant cause of death, perhaps because of the higher proportion of elderly patients infected during this outbreak than during previous outbreaks.

Rémi N. Charrel, M.D., Ph.D.
Xavier de Lamballerie, M.D., Ph.D.
Didier Raoult, M.D., Ph.D.
Université de la Mediterranée, 13385 Marseille, France

4 References

1. 1

   Russell RC, Williams CR, Sutherst RW, Ritchie SA. Aedes (Stegomyia) albopictus -- a dengue threat for southern Australia? Commun Dis Intell 2005;29:296-298
   Medline

2. 2

   Kay BH, Ives WA, Whelan PI, Barker-Hudson P, Fanning ID, Marks EN. Is Aedes albopictus in Australia? Med J Aust 1990;153:31-34
   Web of Science | Medline

3. 3

   Derraik JG. Exotic mosquitoes in New Zealand: a review of species intercepted, their pathways and ports of entry. Aust N Z J Public Health 2004;28:433-444
   Web of Science | Medline

4. 4

   Josseran L, Paquet C, Zehgnoun A, et al. Chikungunya disease outbreak, Reunion Island. Emerg Infect Dis 2006;12:1994-1995
   CrossRef | Web of Science | Medline

Citing Articles (4)

Citing Articles

1. 1

   Alessandra Lo Presti, Massimo Ciccozzi, Eleonora Cella, Alessia Lai, Francesco R. Simonetti, Massimo Galli, Gianguglielmo Zehender, Giovanni Rezza. (2012) Origin, evolution, and phylogeography of recent epidemic CHIKV strains. Infection, Genetics and Evolution
   CrossRef

2. 2

   Lee Ching Ng, Hapuarachchige C. Hapuarachchi. (2010) Tracing the path of Chikungunya virus—Evolution and adaptation. Infection, Genetics and Evolution 10:7, 876-885
   CrossRef

3. 3

   Fabrice Simon, Hélène Savini, Philippe Parola. (2008) Chikungunya: A Paradigm of Emergence and Globalization of Vector-Borne Diseases. Medical Clinics of North America 92:6, 1323-1343
   CrossRef

4. 4

   S.R. Santhosh, P.K. Dash, M.M. Parida, M. Khan, M. Tiwari, P.V. Lakshmana Rao. (2008) Comparative full genome analysis revealed E1: A226V shift in 2007 Indian Chikungunya virus isolates. Virus Research 135:1, 36-41
   CrossRef